mobile app assignment
karthikrao0207
chapter7book.pdf
Getting Started with iOS WHAT’S IN THIS CHAPTER?
! History of iOS
! Getting an iOS development setup
! Objective-C Basics
! iOS Project Basics
! Implementing the Derby App
This chapter is not intended to make you an expert iOS/Objective-C/Cocoa Touch developer; it’s intended to give you an idea of what it takes to create a mobile application on the iOS platform. In our everyday interaction with developers, we have found that many developers dread learning Objective-C, the native language used to create iOS applications. At technical conferences, we have often sat in on beginning-level sessions on how to develop iOS applications, where the presenter has said, “This is very diffi cult, you don’t want to do it.” We have no idea why some of the developer community thinks this way. Code is code (unless you are working with a functional language, but that’s a topic for a different day). Learning a new programming language/framework takes time and a bit of passion — if you are reading this book, we have no doubt in our mind that you can obtain some more Objective-C resources and have what you need to become an Objective-C developer.
THE IPHONE CRAZE The fi rst iPhone was revealed at the Mac World conference in early January 2007, and later released in June of that year. Initially, third-party native applications were not allowed. Apple executives argued that developers could build web (HTML/CSS) applications that would
7
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behave like native iPhone apps. Developers pushed back, and in October 2007 Apple announced an SDK that allowed developers to create native iPhone applications. Many argue that Apple’s decision to allow developers to create native applications was based on the fact that the Android platform was going to be hitting the market soon, and was an extremely open and fl exible platform in which developers could do things that they could not within iOS. The decision to allow native apps within iOS created a new business model for developers, where small projects after work hours have turned into full-fl edged companies. As of February 2012, the Apple App Store contained more than 725,700 applications, which have collectively been downloaded more than 25 billion times.
Since June 2007, iPhones have helped drive the mobile boom. Apple converted a generation of iPod users to iPhone users with simple and effective user interface practices, and made its product “cool.” In May 2010, 59 percent of all mobile web data consumption in the U.S. came from iPhones. The iPhone was a game changer: a personal organizer, gaming platform, web browser, and a phone all in one small package.
Apple in Its Beauty When Steve Jobs introduced the world to the iPhone he proclaimed it as a revolutionary product that would change everything, with a brand-new “multi-touch” interface as breakthrough and as breathtaking as the mouse interface that was introduced in the 1960s. We agree with this statement, and feel that it was the iPhone that kick-started the mobile boom. The iPhone was marketed to consumers, and its ease of use made just about everybody want one.
At the time of its release, the core uniqueness of the iPhone went far beyond its web browser and tightly integrated web functionality. It was six core ideas (outlined in the following list) that changed software applications and websites. Although there were “smartphones” on the market at the time of release of the iPhone, it was not until after the iPhone was released that smartphone manufacturers realized the importance of all of these features being combined to provide a great mobile development platform.
Always on the Internet: A platform that had Internet access wherever cell phone coverage was available opened the door for a new type of application to be developed. Without this functionality, applications such as foursquare (an app that allows you to “check in” to locations) would not exist. This core concept is easy for developers to develop for; the most diffi cult part is coming up with an application idea.
Location-aware: The iPhone also introduced a platform that could detect where you were based on your location. Apart from privacy concerns, this feature has been well received in the developer and user community. Whether it’s a mapping application or an application that lets you tag photos with your location, this feature opened tremendous opportunity for developers to develop location-based apps that did not have to run on a standalone GPS.
Orientation-aware: In addition to location awareness, the iPhone offered a platform that could now detect where in space the device existed. The app that made this feature popular is Urbanspoon. Urbanspoon displays a random restaurant in your area based on criteria
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that you set. If you do not like the restaurant that it picks, you can “shake” the phone and it will choose another one. This is a new type of UI feature that makes interfaces easier to use.
The mobile gaming industry has also taken full advantage of the iPhone’s orientation awareness, releasing many games that allow you use the device as the control stick; for example, moving the iPhone left and right in a race car game makes the car turn left and right, making it feel as though you are actually using a steering wheel.
Innovative input: The iPhone also represented a platform that could detect multiple fi ngers as input, as well as a wide range of gestures such as swipe up, swipe down, tap, dou- ble tap, and so on. With new input types, new UI patterns emerged helping make the small screen of the mobile device easier to deal with.
High-quality, scalable screen: A huge selling point for the iPhone is its high-resolution screen on which movies and photos can be viewed with stunning picture quality.
Power consciousness: Because the iPhone runs on battery, you as a developer need to watch the power consumption of your application. Loops within your code can cause the CPU to work hard, and when the CPU works hard it takes more power, causing your application to drain the device’s battery, which could result in negative comments from users. Years ago, developers worked to keep the size of applications small; for mobile development, you should pay close attention to how an application is coded, and ensure it doesn’t use too much power.
Apple Devices Throughout the years, Apple has produced many different types of mobile devices. From the iPod classic to the iPhone, Apple has created great products, but has not always opened these products up for developers to create apps for or modify them. For the purpose of this chapter, we are going to discuss iPhone, iPod touch, and the iPad. Although each of these devices runs a version of iOS, it’s important to note that older devices may not be able to run the latest version of iOS. For example, if your company tasked you with creating an app for your sales department and the entire sales team had iPhone 3Gs, you could not take advantage of the great features in iOS 5.0, because these devices run only in iOS 4.2.1 and below.
iPhone The iPhone may well be the reason why you are reading this book. Since its introduction in 2007, the iPhone has helped fuel the mobile boom that is currently underway. It has been the thorn in the side of many IT departments, from networking issues (employees bringing their own devices to work, which raises security concerns) to development issues (making your applications run on iOS). From 2007 to December 2011 fi ve devices have been released. It’s important to understand the close relationship between the iOS hardware and software. Meaning, not all versions of iOS will run on all iOS hardware. As device hardware becomes dated, Apple stops releasing iOS updates. Table 7-1 shows iOS hardware with the version of iOS that shipped with the device and the maximum version that can be installed on the device.
The iPhone Craze " 185
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TABLE 7!1 iPhone Hardware and iOS Versions
DE VICE SHIPPE D IOS VE RSION MA X IOS VE RSION
iPhone iOS 1.0 iOS 3.1.3
iPhone 3G iOS 2.0 iOS 4.2.1
iPhone 3GS iOS 3.0
iPhone 4 iOS 4.0
iPhone 4S iOS 5
iPod Touch After the release the original iPhone, Apple added a new product to the iPod product line: the iPod touch. This device was built on iPhone technology, looked identical to the iPhone, and used the same 480 ! 320 multitouch screen, but it was not a phone. This was a great option for consumers who wanted the iPhone experience, but did not want to pay the fees for a cell phone contract. Because of its lack of cellular connectivity, this device could access the Internet only through a wireless Internet connection. Table 7-2 shows iOS hardware with the version of iOS that shipped with the device and the maximum version that can be installed on the device.
TABLE 7!2 iPod touch Hardware and iOS Versions
DE VICE SHIPPE D IOS VE RSION MA X IOS VE RSION
1st generation iOS 1.1 iOS 3.1.3
2nd generation iOS 2.1.1 iOS 4.2.1
3rd generation iOS 3.1.1
4th generation iOS 4.1
iPad Introduced in January of 2010, the iPad was another revolutionary product from Apple. When the iPad was fi rst released, many argued it was just a big iPod touch, which was partially true. You could purchase a cellular data plan so that the device could access data but not phone service. The same great UI that made the iPhone and iPod Touch famous was now available with a 1024 ! 768 screen size.
The iPad pushed the mobile boom even more, with many industries seeing the benefi t that a tablet computer could provide. With two models containing different data storage sizes and access to cellular data, the iPad is leading the way in tablet computing. Table 7-3 shows iOS hardware with the version of iOS that shipped with the device and the maximum version that can be installed on the device.
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Getting the Tools You Need " 187
TABLE 7!3 iPad Hardware and iOS Versions
DE VICE SHIPPE D IOS VE RSION MA X IOS VE RSION
iPad iOS 3.2
iPad 2 iOS 4.3
iPad 3 iOS 5.1
GETTING THE TOOLS YOU NEED Developing for iOS is not a matter of opening up your favorite text editor and going to town. You may need to do a bit of planning, with the fi rst (and most expensive) being hardware. Depending on your development intentions you may need to pay Apple for the honor of being an iOS developer as well.
Hardware Oftentimes we are asked, “Do I really need to have a Mac?” The answer is yes. To develop iPhone, iPod, and iPad applications you must have a Mac. The iPhone SDK runs only on Mac OS X. The only sanctioned hardware for iPhone, iPod, and iPad development is an Intel-based Macintosh.
If you are having a hard time justifying the cost of the hardware, we have had great luck with getting refurbished machines direct from Apple at the following URL:
http://store.apple.com/us/browse/home/specialdeals/mac
Because we work in many different languages and platforms each day, all of the developers we work with have Mac computers. The developers we work with mainly in .NET like to say the Macs are the best Windows machines they have ever had.
Program Levels If you do not have an Apple Developer account, you can create a free account at https:// developer.apple.com/. Having the Apple Developer account allows you to create iOS applications and run them locally on your machine using the iOS Simulator. To deploy applications you have created to a physical device (iPhone, iPad, iPod Touch) you must belong to the iOS Developer program. This is where the money comes in. These programs and prices change from time to time, so please use the following only as a guide, and check https://developer.apple.com/programs/start/ios/ before making any mission-critical decisions.
iOS Developer Program This program level allows developers to distribute apps in the App Store as an individual, a sole proprietor, a company, an organization, a government entity, or an educational institution. The cost for this program is $99 a year, and you are allowed to name 100 devices within your iOS Developer account (which is covered in the device section of this chapter).
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iOS Developer Enterprise Program This program level allows developers to develop proprietary apps for internal distribution within your company, organization, government entity, or educational institution. The cost for this program is $299 a year. This level of the program will not allow you to distribute apps through the App store, but allows ad hoc distributions (distribute directly to a device without using the App Store) to devices in your organization. A valid Dun & Bradstreet (DUNS) number is required, and this program level will take a little bit longer to get enrolled in. We have seen this process take well over a month before acceptance into the program.
iOS Developer University Program This program level allows higher-education institutions to create teams of up to 200 developers that can develop iOS applications. This program level is free, and allows for programs to be tested on physical devices, but does not allow for ad hoc or App Store deployment.
The iOS Provisioning Portal No matter which level of Apple Developer program you registered for, you will have access to the iOS Provisioning Portal. This is the section of the iOS Developer Center that allows you to create the fi les necessary to deploy development and distribution (production) builds onto physical devices.
Certifi cates During the development process of your iOS app, you will more than likely create both a development and a distribution certifi cate. These certifi cates are used to digitally sign the app, and verify you are who you say you are. Figure 7-1 shows the iOS Provisioning Portal Certifi cate section, found within the iOS developer account web interface; here both development and distribution certifi cates are created.
FIGURE 7!1: iOS Provisioning Portal certifi cates
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Getting the Tools You Need " 189
App IDs Each iOS application that you create (that you intend to deploy to a device) needs to be identifi ed on the App IDs section of the iOS Provisioning Portal. The app ID that is created is a unique ID that contains a number from Apple and then a bundle identifi er that you specify. The bundle identifi er is usually in the format com.companyname.appname. As you start to develop more applications, they tend to become messy in this interface, as shown in Figure 7-2.
FIGURE 7!2: iOS Provisioning Portal App IDs
Devices The Devices section in the iOS Provisioning Portal section allows developers to maintain a list of devices in which their iOS applications will be developed. These are the devices that are either used for testing your app or for ad-hoc deployments. The number of devices that you can register on this screen relates to the type of Apple Developer account level you selected. For example, if you registered at the iOS Developer level, you will be able to add 100 devices. This number is 100 per year, meaning if you add 100 devices and then delete 10, you are still out of spaces for accounts until you re-enroll in the program the following year, which will still only have a maximum of 100 devices.
This can become problematic if you are developing iOS applications for multiple customers who have not set up accounts for themselves. It’s important to manage and plan ahead for the amount of devices you will need. Figure 7-3 shows that there is room for only 16 more devices in this account.
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Provisioning Files After the certifi cate, the app ID, and devices have been created/added, you can then create a provi- sioning profi le. The provisioning profi le combines the information about which apps/certifi cates can be installed on which devices. As with certifi cates there will be a Development and Distribution version. Figure 7-4 shows the Provisioning section within the iOS Provisioning Portal.
FIGURE 7!3: iOS Provisioning Portal provisioning devices
FIGURE 7!4: iOS Provisioning Portal Provisioning Profi le
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Getting the Tools You Need " 191
FIGURE 7!5: iOS Dev Center
With all of the Apple administrative tasks complete with regard to setting up an account and obtaining provisioning profi les and certifi cates, you can move on to installing the xCode IDE and starting to work with the iOS SDK.
xCode and the iOS SDK To create native iOS applications, you will need to install both the xCode IDE as well as the iOS SDK. Although you can obtain xCode by using the App Store within Mac OS X, we recommend download- ing xCode and the SDK from the downloads section in the iOS Dev Center as shown in Figure 7-5.
Installation After you follow the steps to install xCode, you should have the xCode IDE as well as a great deal of other useful development tools installed to /Developer/Applications, as shown in Figure 7-6.
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FIGURE 7!7: xCode startup screen
FIGURE 7!6: Development tools
You can start xCode from this directory or by using spotlight. After you start xCode, you should see a screen similar to the one shown in Figure 7-7.
Components of the iPhone SDK The iPhone SDK includes a great number of tools that help create iOS for apps. These tools range from debugging and profi ling to developing. This section lists the most common tools that we use that are included in the iOS SDK.
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iOS Project " 193
xCode xCode is Apple’s Integrated Development Environment (IDE) for creating Objective-C applications. xCode enables you to manage, author, and debug your Objective-C projects.
Dashcode Dashcode is an IDE that enables you to develop web-based iPhone/iPad applications and Dashboard widgets. This product is not in the scope of this book as it is considered an advanced topic.
iPhone Simulator This tool provides a method to simulate an iPhone or iPad device on your Mac, for use with testing your iOS applications.
Interface Builder The Interface Builder, or IB, is a visual editor that is used for designing the user interface for your iOS application.
Instruments Instruments is a suite of tools that helps you analyze your iOS application and monitor for performance bottlenecks as well as memory leaks in real time while attached to an iOS device or iOS Simulator.
The iOS Human Interface Guideline The iOS Human Interface Guideline (HIG) document is one of the most valuable tools to the iOS developer. The iOS HIG describes guidelines and principles that help the iOS developer design a superlative user interface and user experience. It is very important for new iOS developers to read through this document; if you do not develop using the UI principles found in the HIG, your application could be rejected when submitted to the Apple App Store.
The UI standards that Apple puts in place for developers can cause heated conversation. One side of the argument is that developers are locked into obeying a set of rules that cost time and money to learn and implement. The other side of the argument is that Apple has provided a standard UI for applications that have been created for the platform, thus giving the user a great experience no matter who creates the app.
You can fi nd the iOS HIG at http://developer.apple.com/library/ios/#documentation/ UserExperience/Conceptual/MobileHIG/Introduction/Introduction.html#/apple_ref/
doc/uid/TP40006556.
With the xCode IDE and iOS SDK installed, you can now examine what exactly makes up an iOS project with respect to fi les and code.
IOS PROJECT By now you may be thinking that you need to follow a lot of steps before you start creating an iOS application. This may be the reason many seasoned iOS developers try to steer new developers from the platform. Although it takes a lot of steps to get going, they are not complicated or diffi cult; it’s just a matter of learning them and why they exist, which is covered in the remainder of this chapter.
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With all of the “setup” out of the way, we can focus on getting into the IDE and looking at code.
Anatomy of an iOS App iOS .app fi les, the fi les that are actually deployed to the iOS device, are just a set of directories. Although there is an actual binary for the iOS application, you can open the .app fi le and fi nd the images, meta data, and any other resources that are included.
Views iPhone apps are made up of one or more views. Views usually have GUI elements such as text fi elds, labels, buttons, and so on. You can build a view built using the Interface Builder tool, which enables you to drag and drop controls on the view, or you can create a view entirely with code.
Code That Makes the Views Work Because iOS applications follow the MVC design pattern, there is a clean break between the UI and code that provides the application code.
Resources Every iOS application contains an icon fi le, an info.plist fi le that holds information about the application itself and the binary executable. Other resources such as images, sounds, and video are also classifi ed as resources.
Project Structure in Depth When an iOS project is created within xCode, the IDE creates a set of fi les that are ready to run. These fi les provide the basics of what is needed to get going with a new project. Figure 7-8 shows the fi les that are created for a new project named DeleteMe.
Main.m As with any C program, the execution of Objective-C applications start from the main() function, which is the main.m fi le.
AppDelegate.m The AppDelegate receives messages from the application object during the lifetime of your application. The AppDelegate is called from the operating system, and contains events such as the didFinishLaunchingWithOptions, which is an event that iOS would be interested in knowing about.
MainStoryBoard.storyboard This is where the user interface is created. In past versions of xCode/iOS the user interface was stored within .xib (pronounced NIB) fi les. Although this method is still supported, Storyboards are a great improvement over .xib fi les for applications with complex navigation and many views.
FIGURE 7!8: Anatomy of an iOS app
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iOS Project " 195
FIGURE 7!9: Project Navigator
Supporting Files The supporting fi les directory contains fi les such as the plist setting fi les (which contain customiz- able application settings), as well as string resource fi les that are used within your app.
Getting to Know the xCode IDE It’s important to use the correct tool for the job, regardless of whether you are constructing a house or constructing an application. If you are new to xCode, there will be a bit of a learning curve to becoming profi cient with the IDE, but xCode is a top-notch IDE with many features for you to discover.
Navigators The left side of the xCode window is known as the navigator area. A variety of navigators enable you to list the contents of your project, fi nd errors, search for code, and more. The remainder of this section introduces the Project Navigator, the Search Navigator, and the Issue Navigator.
Going from left to right, the project navigator is the fi rst of the xCode navigators; the icon looks like a fi le folder. The Project Navigator simply shows the contents of your project or workspace, as shown in Figure 7-9. Double-clicking a fi le in the Project Navigator opens the fi le in a new window, and single-clicking opens the fi le within the xCode workspace.
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FIGURE 7!10: Search Navigator
The Issue Navigator lists project warnings and errors in real time as you make mistakes. This navi- gator shows any issues preventing your code from compiling, as shown in Figure 7-11.
The Search Navigator helps you locate text within your project or workspace as shown in Figure 7-10.
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iOS Project " 197
FIGURE 7!11: Issue Navigator
Storyboards In iOS versions prior to iOS 5, developers needed to create a separate XIB fi le for each view of their application. A XIB fi le is an XML representation of your controls and instance variables that get compiled into the application. Managing an application that contains more than a few views could get cumbersome.
iOS 5 contained a new feature called storyboards that enables developers to lay out their workfl ow using design tools built within xCode. Apps that use navigation and tab bars to transition between views are now much easier to manage, with a visual representation of how the app will fl ow. Transitions and segues are used to switch between views, without ever having to code them by hand.
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With Storyboards, you will have a better conceptual overview of all the views in your app and the connections between them. Figure 7-12 is an example of a Storyboard for an application that contains a tab bar for navigation to three other views. Segues are the arrows that connect the views.
FIGURE 7!12: Sample Storyboard
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Debugging iOS Apps " 199
DEBUGGING IOS APPS A bug discovered in the fi eld is much more expensive to fi x than bugs that are found on a developer’s machine or during the quality assurance process. Modern-day IDEs provide a great deal of tooling that helps developers fi nd issues in their code before it reaches production.
The iOS Simulator Developers use the iOS Simulator as their fi rst way of fi nding issues with the code they just created. The iOS Simulator enables developers to run their iOS applications on their Macs without having to have a physical iOS device. The Simulator is a great tool for testing your apps quickly. The iOS Simulator is very quick to load, compared to other simulation tools for other mobile platforms. The iOS Simulator is also a great tool for HTML/CSS experts to have installed as well to test mobile webpages rendered within the mobile Safari web browser. Figures 7-13 and 7-14 show the Simulator simulating an iPhone and iPad, respectively.
The term “debugging” was made popular by Admiral Grace Murray Hopper, who was working on a Mark II computer at Harvard University in August 1945, when colleagues discovered a moth stuck in a relay that was causing issues with the system. She made the comment they were “debugging the system.”
FIGURE 7!13: iOS Simulator simulating an iPhone
FIGURE 7!14: iOS Simulator simulating an iPad
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By no means is the Simulator the only tool you should use for testing your app. Although the Simulator is great for testing some things, it lacks in other areas. Not all applications that are avail- able on a physical iOS device are available within the Simulator. Besides that, memory, performance, accelerometer, and camera functionality cannot be tested reliably in the Simulator.
One nice feature of the iOS Simulator is the ability to test various iOS versions, as shown in Figure 7-15.
FIGURE 7!15: iOS Simulator version options
The iOS Simulator is not an emulator. An emulator tries to mimic the behavior of a real device. The iOS Simulator simulates real behavior of the iOS device, but relies on various libraries that are installed on the Mac, such as QuickTime, to perform renderings so that it looks like an actual iPhone. Applications that are deployed to the iOS Simulator are compiled to x86 code, whereas on a real iOS device the code would be compiled to ARM-based code.
Debugging Code As with many modern-day IDEs, Apple and the xCode team have put a great deal of time and effort into creating a set of tools to aid developers in their quest for hunting bugs.
When it boils down to it, developers want tools that make their life easier — tools to step through the code, view log messages, as well as see the state of their variables. xCode provides tools for these features, and much more.
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Debugging iOS Apps " 201
The debugging tools within xCode are located at the bottom of the workspace window. If you do not see the debugging tools, you can click View # Debug Area # Show Debug Area from the xCode menu (see Figure 7-16) to make the debugging tools visible.
FIGURE 7!16: The Debug area
Local Window When the debug area is enabled, the local window shows you a list of all of the variables that are currently within scope of your current breakpoint, and enables you to view details about each vari- able. Figure 7-17 shows the local window, and you can see that an object named derbyNameDetail that is of type NSCFArray contains 908 elements within the array.
FIGURE 7!17: The local window
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Breakpoints You can set breakpoints by clicking on the “gutter” next to the line of code where you would like the application to break. Breakpoints can be enabled and disabled; disabled breakpoints have an opaque blue color, whereas active breakpoints are a solid blue, as shown in Figure 7-18.
FIGURE 7!18: Breakpoints added to the gutter
The top of the debug area contains the Breakpoint toolbar, with tools that enable you to Step Over, Step Into, Step Out, and continue execution of your code. These tools are located in the Debug Area’s toolbar, as shown in Figure 7-19.
FIGURE 7!19: Breakpoint toolbar
Output The output section of the Debug Area gives important information about the execution of the app, as well as displays any log messages you may add in your code. Figure 7-20 shows the application output of an application that logged information received from a web service.
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Debugging iOS Apps " 203
Call Stack When hunting for bugs, it’s useful to follow the execution path of a particular feature, in hopes of fi nding the issue. Figure 7-21 shows the stack trace window within xCode.
FIGURE 7!20: Output window
FIGURE 7!21: The call stack window
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Instruments Suppose you’ve spent the last few weeks working nights to get a version of an iOS app ready for release, but after you use your application for about 15 minutes, it stops for no reason. You think it may be a memory leak of some kind, but are not completely sure because the log messages were pretty cryptic. Instruments is the tool for you. Instruments can be found in the Developer # Application directory. Tools within the Instruments tool suite enable you to track down memory issues and help fi nd slow-running code. Instruments is one of our favorite tools found within xCode, because it helps us fi nd those hard-to-replicate issues. Figure 7-22 shows a few of the trace templates that are available for iOS.
FIGURE 7!22: Instruments analysis tools
OBJECTIVE!C BASICS Objective-C is an object-oriented language based on the C programming language. Objective-C adds Smalltalk-style messaging, which throws even the seasoned polyglot programmer for a loop when starting with this language. Objective-C was created in the early 1980s by Brad Cox and Tom Love, and gained popularity when Steve Jobs and NeXT licensed the language from them, and made Objective-C the main language on NeXT’s NextSTEP operating system.
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Objective-C Basics " 205
Objective-C requires developers to declare a class in an interface and then defi ne the implementation, something that non-C developers fi nd off-putting about the language. If you are comfortable developing in C languages, Table 7-4 will help you fi nd your bearings when getting started with Objective-C.
TABLE 7!4: Equivalencies between C languages and Objective-C
C/C++ OBJEC TIVE!C
#include “library.h” #import “library.h”
this self
private: @private
protected: @protected
public: @public
Y = new MyClass(); Y = [[MyClass alloc] init];
try, throw, catch,!fi nally @try, @throw, @catch, @fi nally
Classes The interface of Objective-C classes is defi ned in a header fi le for each interface. Usually the fi lenames of the header match the class name. For example, you can create a header fi le named dog.h:
@interface Dog : Animal { // instance variables }
// Method declarations
@end
You are telling the compiler that a new class named Dog, which is a subclass of animal, is being declared. Any instance variables are declared between the curly brackets, and methods are declared between the end of the curly bracket and the @end keyword.
The actual implementation of the Dog class would look like this:
#import “dog.h” @implementation Dog // method definitions @end
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Instance Variables The attributes that are declared between the curly brackets are instance variables. Instance variables are declared like local or global variables, but have a different scope. Instance variables by default are visible in all instance methods of a class and its subclasses.
Methods Methods can be declared as either instance methods or class methods. Instance methods are called by sending a message directly to the instance of the class, which means you need to have your own instance of the class before you can call these methods. Instance methods are prefi xed with a minus sign (-). The following is an example of the declaration for an instance method that returns the name of the animal, and takes no parameters:
-(NSString) getNameOfAnimal;
A class method does not require an instance of a class. You call a class method by sending a message to the unique class object. C# or Java developers may recognize class methods as static methods. The following method returns an array containing a list of all nonextinct animals:
+(NSArray) getNonExtinct();
Calling Methods You may have noticed that Objective-C is heavy on the use the brackets. In Objective-C, methods are not called in the traditional sense; their objects are sent messages. The syntax for sending messages is to enclose the name of the object and the message with square brackets:
[object method]; [object methodWithInput:input];
Methods can return values:
output = [object methodWithOutput]; output = [object methodWithInputAndOutput:input];
Objective-C 2.0 provides a dot-notation that can be used to invoke methods. Many new Objective-C developers like this syntax because it looks like other languages in which they are more profi cient.
Implementation in Non-Dot Notation:
int lastLocation = [myAnimal getLastLocation];
Implementation in Dot Notation:
int lastLocation = myAnimal.getLastLocation;
Control Structures Oftentimes when learning a new language, we like to look at the control structures to get an idea of how to implement these types of structures.
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Objective-C Basics " 207
If Statements If statements are pretty straightforward in Objective-C. The following example checks to see if an array of animal names contains a name “luna”:
NSArray *animalNames = ... NSString* nameOne = @”luna”;
if ( [animalNames containsObject: nameOne] ) { ... } else { // do something else }
For Loops The standard C for loop can be used to iterate over an enumerable object such as an array in Objective-C. The following example loops over an array of animal objects and prints their location to the console screen:
NSArray *animals = ... NSUInteger animalCount = [animals count];
for (j=0; j < animalCount; j++ ) { NSLog([[animals objectAtIndex: j] getLastLocation]); }
Fast Enumeration Objective-C 2.0 also gives us new syntax for a control structure called Fast Enumeration. Fast Enumeration is easier for developers to code, and runs faster than other traditional loops such as for and while loops.
NSMutableArray *animals = ...
for (Animal *singleAnimalObject in animals ) { NSLog([singleAnimalObject getLastLocation]); }
Try Catch Error handling is one of those developer religious debates that we are not going to get into in this chapter. We will tell you that exception handling in Objective-C is expensive, and was designed for catching programmer errors or other nonrecoverable problems. If you can test for an error condition in advance, you should do so rather than catching exceptions. Your code will run must faster.
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The following example illustrates the structure of exception handling in Objective-C:
@try { // code that may cause the exception } @catch (NSException *e) { //exception is caught and logic should be added to handle the exception } @finally { // code that should be executed no matter if an exception has occurred or not. }
Now that the Objective-C basics are covered, you can dive in and create your fi rst native iOS app with Objective-C and the iOS SDK.
HELLO WORLD APP Before you can run, you need to walk. We are not huge fans of creating Hello World–type apps, but with the iOS SDK and Objective-C so different from many other application frameworks, we felt it made sense.
This section illustrates the steps needed to create a simple iOS application that contains a label and a button. When the button is touched, the text in the label changes. This allows us to explain xCode and the various tools contained within xCode that are required when making an iOS application.
Creating the Project After opening xCode, create a Single View Application project type found under the iOS project types, as shown in Figure 7-23. When you select a Single View Application, xCode generates the fi les you need to start creating an iOS app that has only one view.
FIGURE 7!23: iOS project template
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Hello World App " 209
After you select a project template, you are prompted to enter the project level options as shown in Figure 7-24.
FIGURE 7!24: iOS project options
For this example, enter a product name of Hello World, target the iPhone, set the company identifi er to whatever you choose, and leave the default settings for the rest.
Product Name xCode uses the product name you enter to name your project and the application. If you want your application name to show up differently in iOS, there is an option in the .plist fi le to set the display name of the app.
Company Identifi er This identifi er is used to generate the bundle identifi er for the iOS app. The company identifi er is usually something like com.gravityworksdesign.
Bundle Identifi er The bundle identifi er is automatically generated for you and is a combination of the product name and company identifi er. This identifi er is used when provisioning your app to be installed on devices. The bundle identifi er is unique to an app, and the Apple developer tools will not allow you to provi- sion an app when an existing app is using the same bundle identifi er.
Class Prefi x The text you enter into the Class Prefi x fi eld is prefi xed to the fi lenames and class names of all header and implementation fi les.
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Device Family This option enables you to target which type of device your application will run on: iPhone, iPad, or Universal. Universal allows your application to be run on both iPhone and iPad. Beneath Device Family are three checkboxes:
! Use Storyboard: As mentioned previously in this chapter, Storyboards are new to iOS 5. They are a great feature to aid in iOS development, but some developers are stuck in their ways, and may not like Storyboards (or may have some other valid reason). This option creates .xib fi les for each view just like previous versions of the iOS SDK/xCode.
! Use Automatic Reference Counting: A new feature to iOS 5, automatic reference counting manages memory so that developers do not have to do it themselves. Automatic reference counting can be considered a type of garbage collection mechanism. If you are creating an application that needs to be deployed on versions of iOS less than 5, automatic reference counting is not supported, so this option must be disabled.
! Include Unit Tests: When this option is checked, xCode generates the fi le structure for a set of unit tests for your iOS application. It is your responsibility to create and maintain these unit tests.
After the project has been created, you will see a screen similar to Figure 7-25. This screen contains the project level options for your app. On this screen, you can add a launch image (splash screen), the app icon, target-specifi c device orientations, target-specifi c versions of iOS, and the list goes on and on.
FIGURE 7!25: iOS Project screen
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Hello World App " 211
You do not have to do anything on this screen for the Hello World app.
Creating the User Interface The user interface is fairly simple for this app. It has a label and a button. We are not going to get fancy with any UI elements, but feel free to explore and extend the application to get a feel of your fi rst iOS app.
Controls in the View From the Project Navigator, select the MainStoryboad.storyboard fi le. You then need to put a label control on the view. You can fi nd the controls that you have access to on the bottom right of the IDE in the Object Library. Find the label control, and drag the control to the storyboard. Your app should look similar to Figure 7-26 now.
FIGURE 7!26: Hello World Storyboard
When you click the label in the storyboard, you should see settings that are specifi c to that control in the upper-right side of xCode in the Identity Inspector. The Identity Inspector is a settings tool, which enables you to control font color, size, and other options specifi c to the control you are working with. Figure 7-27 shows the Identity Inspector interface when editing the settings for a button.
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The next step is to add a button to the view. Buttons are added like the label control, by dragging the control onto the view. In this example set the button text to say Change Label.
Wiring Up the Controls By this point you should have a view that contains two controls: a label and a button. If you run your application, you should see the interface you developed in the iOS Simulator, but you have not told the applica- tion to do anything yet. Wiring up the controls to events can be tricky for new developers on this platform.
The fi rst thing you want to do is to show the Assistant Editor. You can toggle this editor on and off by selecting the “Tuxedo” button near the upper-right side of the IDE, as shown in Figure 7-28.
Depending on where you have the Assistant Editor set to show, yours may be placed differently than the following screenshots. To change where exactly on the screen the Assistant Editor shows, you can select View # Assistant Editor from the xCode menu and then select where you would like the editor to show.
Defi ning the Label The next step is a bit tricky. You need to defi ne your controls in the header fi le. To do this, hold down the Control key on the keyboard, and click and drag your label control from the storyboard to the header fi le that is shown in the Assistant Editor (see Figure 7-29).
FIGURE 7!27: xCode control-specifi c settings
FIGURE 7!28: Toggling the Assistant Editor
FIGURE 7!29: Defi ning controls
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Hello World App " 213
Once you release the mouse, a dialog box appears asking you to name the object. We like to follow Hungarian notation for control names, so name the label lblChangeMe as shown in Figure 7-30.
Wiring the Button Wiring the event for the button is similar to defi ning the event. If you right-click the button you see a dialog box similar to the one shown in Figure 7-31.
You are most interested in the Touch Up Inside event, which is the event that occurs when a fi nger is raised off the control. This is where you want to add logic . To do this, simply click the circle next to the Touch Up Inside event, and drag it to the Assistant Editor as shown in Figure 7-32. As with the label, you are prompted for a name; name this one btnChangeText_click.
FIGURE 7!30: Naming the control
FIGURE 7!31: Right-clicking a control
FIGURE 7!32: Defi ning the Touch event
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Like all Hello World–type apps, the intention was to give you an idea of the project structure and basic interaction between the UI and code. To build upon this, the next section tackles a more complex native iOS app.
BUILDING THE DERBY APP IN IOS The idea of the Derby App is to build the same app over all of the mobile platforms covered in this book. The iOS version is very similar to the other versions that you have built thus far or will build in future chapters.
Writing the Code With the UI completed and wired up, you can now tell your app what you want the Touch event to do when touched. To do this, open the ViewController.m fi le, and add the following method:
- (IBAction)btnChangeText_click:(id)sender { NSString* newText = @”My new text”; lblChangeMe.text = newText; NSLog(newText); }
This code defi nes a new string, sets the label text to the new string, and then logs the new string to the event viewer. If you followed the steps correctly, your app should look similar to Figure 7-33 in your iOS Simulator, and you should see a log fi le similar to Figure 7-34 in the output window of xCode.
FIGURE 7!33: Completed Hello World iOS app FIGURE 7!34: Output of the Hello World app
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Building the Derby App in iOS " 215
The requirements are to list the roster from the Lansing Derby Vixens roller derby team as the primary function, and then list all the roller derby teams in the world with the ability to see their team rosters.
User Interface The derby app contains a list of data, so you use table views throughout the application to show the information to the user. Start by creating a new tabbed application within xCode as shown in Figure 7-35.
FIGURE 7!35: Creating a tabbed app
By default xCode creates a new iOS application that contains a Storyboard with tabbed navigation. Your project needs to contain three table views and one Navigation controller. The table views are used to the list the data about the derby teams and rosters, and the navigation controller enables you to create a “back stack” that will allow users to navigate back to the team names table view, when fi nished viewing the team’s roster data. Start by dragging three Table View Controllers from the Object Library onto the storyboard, and then remove the views that were added by default.
Once the previous views are removed and the table views are added, you need to connect them to the navigation controller. To do this, Control-click the Tab Bar Controller icon on the Tab Bar View, within the Storyboard, and drag it to the new view as shown in Figure 7-36.
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When prompted, select Relationship for the type of Storyboard segue from the dialog box shown in Figure 7-37. This adds a new icon to the Tab Bar Controller for the Table View that was just linked.
Setting the segues for the remainder of the storyboard is very similar. Use the Control-drag functionality to link the main Tab Bar Controller to the Navigation Controller, then link the Navigation Controller to the League Table View, and the League Table View to the Details Table View as shown in Figure 7-38.
FIGURE 7!36: Connecting view to tab bar
FIGURE 7!37: Selecting relationship for segue
FIGURE 7!38: Linking the Navigation Controller for the leagues
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Building the Derby App in iOS " 217
The segue that is created from the Leagues view needs to have an identifi er of “Details.” This enables you to trigger this particular segue from within code. To do this, click the segue (the arrow between the Leagues Table View and the Details Table View), and open the Identity Inspector. In the Identifi er box enter Details as shown in Figure 7-39.
When you have completed this task, you should have a storyboard that looks similar to Figure 7-40. For complete code samples, visit this book’s page on http://www.wrox.com and click the Download Code tab.
FIGURE 7!39: Adding an identifi er to a segue
FIGURE 7!40: Relationships completed
Team Roster With the storyboard in place, you can now write the code to populate the table views. Start with the Team Roster tab, which will go out to a web service, and obtain a list of all the Lansing Derby Vixens.
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First create a new class named VixensViewController:
@interface VixensViewController : UITableViewController @property(nonatomic, retain) NSArray *listData; @end
In the viewDidLoad method within the implementation fi le, add your logic to go out the web service and get the roster for the Lansing Derby Vixens. Notice the fi lter criteria contained within the URL.
- (void)viewDidLoad { [super viewDidLoad]; NSMutableArray *array = [[NSMutableArray alloc] init]; // go out to the service and get the data NSError *error = nil; NSURL *derbyService = [NSURL URLWithString: @”http://derbynames.gravityworksdesign.com/DerbyNamesService.svc/ DerbyNames?$filter=League%20eq%20’Lansing%20Derby%20Vixens’”]; NSData *data = [NSData dataWithContentsOfURL:derbyService];
// Use native functions to parse the JSON NSDictionary *derbyNames = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:&error]; NSArray* derbyNameDetail = [derbyNames objectForKey:@”d”]; // loop through all of the derby objects only add the name object to the array for (NSDictionary* derbyItem in derbyNameDetail) { NSString *name = [derbyItem objectForKey:@”Name”]; NSString *league = [derbyItem objectForKey:@”League”]; NSString *number = [derbyItem objectForKey:@”Number”]; NSLog(@”Names: %@-%@-%@”, name, league, number); [array addObject:name]; }
self.listData = array; }
iOS 5 is the fi rst version of the iOS SDK that contains built-in support for parsing JSON strings. This is great because you do not have to depend on a third-party tool. The last line in the method self.listData = array; sets the data that you will use to bind the data to the table view.
For the table view to know how many rows it needs to select, you must implement the numberOfRowsInSection method. In this case, just return the count of the number of items in the listData array, which is the array that you populated when the view loaded.
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Building the Derby App in iOS " 219
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return [self.listData count]; }
The magic really happens in the cellForRowAtIndexPath method. This method is called for the number of times that was returned in the numberOfRowsInSection. In the code, you create a new cell, get the data for the correct position in the listData array, and then return the cell you created, which will be added to the table:
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @”Cell”; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier]; } // Configure the cell... NSUInteger row = [indexPath row]; cell.textLabel.text = [listData objectAtIndex:row]; return cell; }
Details The next class you need to create is DetailViewController. This is the code that drives the details that are displayed when a team name is selected.
#import <UIKit/UIKit.h>
@interface DetailViewController : UITableViewController
@property (nonatomic, retain) NSString *data; @property(nonatomic, retain) NSArray *listData;
@end
The logic for this is very similar to what you just implemented for the roster view, but you are adding a new string named data, which holds the string value of the team for which you want to receive the roster. This string is passed into this view, allowing you to fi lter which roster is shown. You need to implement both the numberOfRowsInSection and cellForRowAtIndexPath methods exactly as you did with the roster view.
You can see that the viewDidLoad code is very similar, but you take the data string, encode it for URL use, and then append it to your URL that fi lters which team to get the roster for:
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- (void)viewDidLoad { [super viewDidLoad]; // build our URL to get the data from NSString* url = @”http://derbynames.gravityworksdesign.com/DerbyNamesService.svc/ DerbyNames?$filter=League%20eq%20’”; NSString* escapedUrlString = [data stringByAddingPercentEscapesUsingEncoding: NSASCIIStringEncoding]; NSString *urlToGetData = [NSString stringWithFormat:@”%@%@’”, url,escapedUrlString]; // get the data NSMutableArray *array = [[NSMutableArray alloc] init]; NSError *error = nil; NSURL *derbyService = [NSURL URLWithString: urlToGetData]; NSData *rosterData = [NSData dataWithContentsOfURL:derbyService]; NSDictionary *derbyNames = [NSJSONSerialization JSONObjectWithData:rosterData options:NSJSONReadingMutableLeaves error:&error]; // process the data NSArray* derbyNameDetail = [derbyNames objectForKey:@”d”]; for (NSDictionary* derbyItem in derbyNameDetail) { NSString *name = [derbyItem objectForKey:@”Name”]; NSString *league = [derbyItem objectForKey:@”League”]; NSString *number = [derbyItem objectForKey:@”Number”]; NSLog(@”Names: %@-%@-%@”, name, league, number); [array addObject:name]; } // return the data self.listData = array; }
Leagues and Team Names Listing all of the team names is very similar to the code you just created for displaying the roster and the details. Start by creating a new class named LeagueTableViewController:
#import <UIKit/UIKit.h>
@interface LeagueTableViewController : UITableViewController @property(nonatomic, retain) NSArray *listData; @end
The viewDidLoad method will look very similar, but notice the URL you are using this time, which is different from the previous URL. This URL returns a JSON string containing the team names.
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Building the Derby App in iOS " 221
- (void)viewDidLoad { [super viewDidLoad];
NSMutableArray *array = [[NSMutableArray alloc] init];
// go out to the service and get the data NSError *error = nil; NSURL *derbyService = [NSURL URLWithString: @”http://derbynames.gravityworksdesign.com/ DerbyNamesService.svc/Leagues”]; NSData *data = [NSData dataWithContentsOfURL:derbyService]; // Use native functions to parse the JSON NSDictionary *derbyNames = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableLeaves error:&error]; // loop through the derby objects returned only add the name object to the array NSArray* derbyNameDetail = [derbyNames objectForKey:@”d”]; for (NSDictionary* derbyItem in derbyNameDetail) { NSString *name = [derbyItem objectForKey:@”LeagueName”]; NSLog(@”Names: %@”, name); [array addObject:name]; } self.listData = array; }
What’s new in this view is the functionality to select a row. When the row is selected, a new view that contains the list of team members for that derby team is opened. To accomplish this you fi rst need to implement the didSelectRowAtIndexPath method. In your method you get the cell and then call the performSegueWithIdentifier method.
- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath { UITableViewCell *cell = [self tableView:tableView cellForRowAtIndexPath:indexPath]; [self performSegueWithIdentifier:@”Details” sender:cell]; }
After the user selects the table row, you need to pass the data in the cell that the user touched to the details view, which will show the roster for that particular team. The performSeagueWithIdenti- fier method is the code that actually switches the views for you. In this case, you are following a segue with the name of Details. Before the transfer is performed, you set the destination controller of the segue to a new DetailViewController and set the data property on the detail view to the contents of the cell, in this case the name of the derby team for which you want to see the roster.
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- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender { if ([segue.identifier isEqualToString:@”Details”]) { DetailViewController *detailView = segue.destinationViewController; UITableViewCell *dataCell = (UITableViewCell *)sender; [detailView setData:dataCell.textLabel.text]; } }
After all of the code has been added to the new View Controllers you created, you need to go back to the Storyboard and attach them as shown in Figure 7-41. You do this using the Identity Inspector found near the upper right of the screen when you are viewing the storyboard. Map each view to the correct class that was created.
With this logic in place, you should now have a working Derby App created natively with iOS. Your app should look similar to Figure 7-42.
FIGURE 7!41: Attaching a class to a View
FIGURE 7!42: Completed Derby application
This section of the iOS chapter covered creating a native iOS mobile app using xCode and Objective-C. The Derby app example covers the major functionality that a mobile developer would encounter when creating an app, such as creating UI and communicating with an external data service. By no means does this section give complete coverage as to what it takes to be an iOS developer, but it should lead you in the right direction.
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Other Useful iOS Things " 223
OTHER USEFUL IOS THINGS The two example projects up to this point have provided the basics for creating iOS applications that will go out to a web service and render the collected data on the screen. By no means do we feel that we have covered every possible situation you may need to develop a solution for, so we wanted to fi nish this chapter by providing a few more short examples that will help you out when discovering how the iOS framework works.
O" ine Storage Even if your application is using a web service for retrieving information, at some point you may need to save information on the device. Depending on the size and type of data, you have a few different options.
Plist Property lists are the simplest way to store information on the device. In the Mac world, many applications use the plist format to store application settings, information about the application, and even serialized objects. It’s best to keep the data contained in these fi les simple and small, though.
The following example fi nds the path to a plist stored in the supporting fi les directory, with a name of example. It then loads the plist into a dictionary object, and loops through each time writing the contents of each item in the plist to the debug console.
- (void)getValuesFromPlist { // build the path to your plist NSString *path = [[NSBundle mainBundle] pathForResource: @”example” ofType:@”plist”]; // load the plist into a dictionary NSDictionary *pListData = [[NSDictionary alloc] initWithContentsOfFile:path]; // loop through each of the Items in the property list and log for (NSString *item in pListData) NSLog(@”Value=%@”, item); }
If you want to get a single item out of the plist the code is very similar. The following example cre- ates a function named outputSinglePlistValue that takes in the name of the item you want to output, itemName. You then just use the objectForKey method to get the value of a specifi c key in the dictionary that was returned.
- (void)outputSinglePlistValue: (NSString*) itemName { // build the path to your plist NSString *path = [[NSBundle mainBundle] pathForResource:
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@”example” ofType:@”plist”]; // load the plist into a dictionary NSDictionary *pListData = [[NSDictionary alloc] initWithContentsOfFile:path]; NSString *value = [pListData objectForKey:itemName]; NSLog(@”Name=%@-Value=%@”, itemName,value); }
To write to the plist fi le, again you need to load the plist into a dictionary, this time a mutable dictionary that will allow you to make changes. You can use the setValue method to change the value of a key, and then write the plist database to a fi le named example.
- (void)writeToPlist { NSString *path = [[NSBundle mainBundle] pathForResource: @”example” ofType:@”plist”];
NSMutableDictionary* pListData = [[NSMutableDictionary alloc] initWithContentsOfFile:path];
[pListData setValue:@”Modified Value” forKey:@”Test1”]; [pListData writeToFile:path atomically: YES]; }
Core Data If the data that you need to persist on the device is nontrivial, meaning there is a great deal of it or its complex, Core Data is the way to go. Core Data is described by Apple as a “schema-driven object graph management and persistence framework.” Core Data is not an ORM (Object Relational Mapper). Core Data is an API that abstracts the actual data store of the objects. Core Data can be confi gured to store these objects as a SQLite database, a plist, custom data, or a binary fi le. Core Data has a steep learning curve, but is well worth learning more about if your app will have a great deal of data held within.
GPS One of the great benefi ts to mobile devices is the GPS functionality. Once you are able to get over the hurdles of learning the basic functions within the iOS platform, starting to work with the GPS functions can be a great deal of fun.
The GPS functions are located in the CoreLocation framework, which is not added to a new proj- ect by default. To do this, you will need to click the Build Phases tab on the project settings page as shown in Figure 7-43.
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Other Useful iOS Things " 225
Once on the Build Phases tab, expand the Link Binary With Libraries section, and click the + button. You are then prompted with a list of frameworks to add. Select the CoreLocation.framework as shown in Figure 7-44.
FIGURE 7!43 Build Phases tab
FIGURE 7!44: Adding the CoreLocation framework
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With the reference to the CoreLocation framework in place, you are now ready to start working with the GPS functionality. Start with the ViewController.h fi le. The CLLocationManager class will send out updates anytime the location is changed. These updates are sent out using the delegate pattern, which simply means your view controller needs to implement the CLLocationManagerDelegate protocol.
@interface ViewController : UIViewController <CLLocationManagerDelegate>{ CLLocationManager *locationManager; }
Once your header fi le implements the correct delegate, you can initialize the location manager in the ViewDidLoad method of the ViewController.h fi le. When you initialize this class, you have control over how frequently you want to receive updates as well as how accurately you want them.
// GPS Example locationManager = [[CLLocationManager alloc] init]; locationManager.delegate = self; locationManager.distanceFilter = kCLDistanceFilterNone; // get GPS DatalocationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters; [locationManager startUpdatingLocation];
The last step you need to perform is to implement the method that is called whenever the location has changed. In this method you convert the raw GPS data that is sent from iOS to the common format of Degrees, Minutes, and Seconds, and then log the latitude and longitude:
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation { // turn the raw lat info into degrees, minutes, seconds int latDegrees = newLocation.coordinate.latitude; double latDecimal = fabs(newLocation.coordinate.latitude - latDegrees); int latMinutes = latDecimal * 60; double latSeconds = latDecimal * 3600 - latMinutes * 60; NSString *latitude = [NSString stringWithFormat:@”%d° %d’ %1.4f\””, latDegrees, latMinutes, latSeconds]; NSLog(latitude); // turn the raw long into degrees, minutes, seconds int longDegrees = newLocation.coordinate.longitude; double longdecimal = fabs(newLocation.coordinate.longitude - longDegrees); int longMinutes = longdecimal * 60; double longSeconds = longdecimal * 3600 - longMinutes * 60; NSString *longitude = [NSString stringWithFormat:@”%d° %d’ %1.4f\””, longDegrees, longMinutes, longSeconds]; NSLog(longitude); }
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Summary " 227
When you run this example project you are prompted from iOS whether you want to allow this application to use your current location, as shown in Figure 7-45. The Simulator will return the GPS location for Cupertino, California. So if you are looking for more accurate data, you will need to deploy the app to a physical iOS device.
SUMMARY This chapter spent a great deal of time describing the iOS platform. After reading this chapter, you should be comfortable installing xCode and getting started developing and debugging your fi rst iOS app. Developing for iOS should not be rushed into. Even though corporate executives are pushing development teams to create applications for the iOS platform, you should take a step back and make sure it really makes sense.
Apple has helped push the world into the mobile boom that we are in now, and it is constantly innovating and pushing the mobile industry. Choosing one platform helps developers focus their skills, but locks them into that platform. Apple is known for not being kind to developers, by providing tools that are not the easiest to work with. However iOS fi ts into your strategy, be aware that Apple has a large market share, and will be around for a long time.
The following chapter will take a dive into what it takes to develop the same type of mobile app on the Windows Phone 7 platform.
FIGURE 7!45: iOS prompts for use of current location
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