DIscussion - 10 hours

Professor Michael G. Solomon

BLCN 631 – Blockchain Implementation

EFD Chapter 7 – Building Your First Ethereum Apps

Setting up Your Project

• Everything starts with a project

• We’ll use Truffle to manage projects

• Edit the config file first

• Use VS Code

• Use Ganache settings (next slide, please)

• HOSTNAME

• PORT NUMBER

Ganache – Host & Port

Exploring Ganache

Simple Smart

Contract

• New language – changes frequently

We’ll use the Solidity language

• Blockchain access costs $$ (crypto) • What gets written in a blockchain

• Stays in the blockchain

Remember

• Returns a string – “Hello world!”

First smart contract

HelloWorld.sol

pragma solidity ^0.5.0;

contract HelloWorld {

string private helloMessage = "Hello world";

function getHelloMessage() public view returns (string memory) {

return helloMessage;

}

}

Writing Smart

Contract Code

• Create new file - contracts/HelloWorld.sol

• Create new file - migrations/2_contract_migrations.js

• Type the following code:

var HelloWorld =

artifacts.require("HelloWorld");

module.exports = function(deployer) {

deployer.deploy(HelloWorld);

};

Compiling Smart

Contracts

• EVM can’t run source code

• Smart contracts must be compiled into bytecode

• EVMs run bytecode

• Open new terminal (Terminal -> New Terminal)

• Type: truffle compile

Deploying a Smart Contract

• Make sure Ganache is running

• In VS Code terminal, type:

• truffle deploy –reset

• Go look at Ganache again

• Account[0] balance, blocks, transactions

Invoking a Smart

Contract Function

• Invoke smart contract functions

• At the VS code terminal prompt

• Three separate commands below:

truffle console

HelloWorld.deployed().then(function(in

stance) {return instance });

HelloWorld.deployed().then(function(in

stance) {return

instance.getHelloMessage() });

Summary

Exploring your development environment

Coding in Solidity

Writing smart contracts

Using blockchain data