使用 Solidity 和 Truffle 在 Ethereum 區塊鏈開發智能合約

前言

本文使用 Ethereum 智能合約實作一個「To-Do List」應用程式。

前置作業

  1. 安裝 Ganache 測試工具,並啟動應用程式。
  2. 安裝 MetaMask 錢包。

安裝依賴

安裝 Truffle 命令列工具。

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npm install -g [email protected]

查看版本。

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truffle version
Truffle v5.0.2 (core: 5.0.2)
Solidity v0.5.0 (solc-js)
Node v14.17.3

建立專案

建立專案。

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mkdir eth-todo-list
cd eth-todo-list

新增 .gitignore 檔。

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/node_modules

新增 package.json 檔。

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{
"name": "eth-todo-list",
"version": "0.1.0",
"description": "",
"main": "truffle-config.js",
"directories": {
"test": "test"
},
"scripts": {
"dev": "lite-server",
"test": "echo \"Error: no test specified\" && sexit 1"
},
"author": "",
"license": "ISC",
"devDependencies": {
"bootstrap": "4.1.3",
"chai": "^4.1.2",
"chai-as-promised": "^7.1.1",
"chai-bignumber": "^2.0.2",
"lite-server": "^2.3.0",
"nodemon": "^1.17.3",
"truffle": "5.0.2",
"truffle-contract": "3.0.6",
"web3": "^0.20.0"
}
}

安裝依賴套件。

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npm install

使用 truffle 指令初始化專案。

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truffle init

新增 contracts/TodoList.sol 檔。

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// SPDX-License-Identifier: MIT
pragma solidity >=0.5.0;

contract TodoList {
uint public taskCount = 0;
}

修改 truffle-config.js 檔,將網路指向 Ganache 的端點。

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module.exports = {
networks: {
development: {
host: "127.0.0.1",
port: 7545,
network_id: "*",
},
},
solc: {
optimizer: {
enabled: true,
runs: 200,
},
},
};

新增 migrations/2_deploy_contracts.js 檔。

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const TodoList = artifacts.require("TodoList");

module.exports = function(deployer) {
deployer.deploy(TodoList);
};

編譯智能合約。

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truffle compile

執行部署腳本,將合約部署到本地測試鏈上。

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truffle migrate

互動介面

進入 Truffle 互動介面,與合約進行互動。

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truffle console

取得 TodoList 合約的內容。

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> todoList = await TodoList.deployed()

取得 TodoList 合約的地址。

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> todoList.address
'0x21875AacaeDbE8F9CF0ce0a72cEF4665BF25e058'

取得 TodoList 合約中,變數 taskCount 的值。

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> (await todoList.taskCount()).toNumber()
0

離開互動介面。

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> .exit

合約實作

修改 contracts/TodoList.sol 檔。

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// SPDX-License-Identifier: MIT
pragma solidity >=0.5.0;

contract TodoList {
uint public taskCount = 0;

struct Task {
uint id;
string content;
bool completed;
}

mapping(uint => Task) public tasks;

event TaskCreated(
uint id,
string content,
bool completed
);

event TaskCompleted(
uint id,
bool completed
);

constructor() public {
createTask("Check out https://github.com/memochou1993");
}

function createTask(string memory _content) public {
taskCount++;
uint id = taskCount;
tasks[id] = Task(id, _content, false);
emit TaskCreated(id, _content, false);
}

function toggleCompleted(uint _id) public {
Task memory _task = tasks[_id];
_task.completed = !_task.completed;
tasks[_id] = _task;
emit TaskCompleted(_id, _task.completed);
}
}

編譯智能合約。

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truffle compile

重新執行部署腳本。

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truffle migrate --reset

設置錢包

在 MetaMask 錢包新增一個測試網路:

將 Ganache 中帳戶的私鑰匯入至 MetaMask 錢包。

實作前端

新增 bs-config.json 檔,用來配置 lite-server 伺服器。

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{
"server": {
"baseDir": [
"./src",
"./build/contracts"
],
"routes": {
"/vendor": "./node_modules"
}
}
}

新增 src/index.html 檔。

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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>To-Do List</title>
<link href="vendor/bootstrap/dist/css/bootstrap.min.css" rel="stylesheet">
<style>
main {
margin-top: 60px;
}
#content {
display: none;
}
form {
width: 350px;
margin-bottom: 10px;
}
ul {
margin-bottom: 0px;
}
#completedTaskList .content {
color: grey;
text-decoration: line-through;
}
</style>
</head>
<body>
<nav class="navbar navbar-dark fixed-top bg-dark flex-md-nowrap p-0 shadow">
<a class="navbar-brand col-sm-3 col-md-2 mr-0" href="https://github.com/memochou1993" target="_blank">To-Do List</a>
<ul class="navbar-nav px-3">
<li class="nav-item text-nowrap d-none d-sm-none d-sm-block">
<small><a class="nav-link" href="#"><span id="account"></span></a></small>
</li>
</ul>
</nav>
<div class="container-fluid">
<div class="row">
<main role="main" class="col-lg-12 d-flex justify-content-center">
<div id="loader" class="text-center">
<p class="text-center">Loading...</p>
</div>
<div id="content">
<form onSubmit="App.createTask(); return false;">
<input id="newTask" type="text" class="form-control" placeholder="Add task..." required>
<input type="submit" hidden="">
</form>
<ul id="taskList" class="list-unstyled">
<div class="taskTemplate" class="checkbox" style="display: none">
<label>
<input type="checkbox" />
<span class="content">Task content goes here...</span>
</label>
</div>
</ul>
<ul id="completedTaskList" class="list-unstyled">
</ul>
</div>
</main>
</div>
</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
<script src="vendor/bootstrap/dist/js/bootstrap.min.js"></script>
<script src="vendor/web3/dist/web3.min.js"></script>
<script src="vendor/truffle-contract/dist/truffle-contract.js"></script>
<script src="app.js"></script>
</body>
</html>

新增 src/app.js 檔。

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App = {
loading: false,
contracts: {},

load: async () => {
await App.loadWeb3()
await App.loadAccount()
await App.loadContract()
await App.render()
},

loadWeb3: async () => {
if (typeof web3 !== 'undefined') {
App.web3Provider = web3.currentProvider
web3 = new Web3(web3.currentProvider)
} else {
window.alert("Please connect to Metamask.")
}
// Modern dapp browsers...
if (window.ethereum) {
window.web3 = new Web3(ethereum)
try {
// Request account access if needed
await ethereum.enable()
// Acccounts now exposed
web3.eth.sendTransaction({/* ... */})
} catch (error) {
// User denied account access...
}
}
// Legacy dapp browsers...
else if (window.web3) {
App.web3Provider = web3.currentProvider
window.web3 = new Web3(web3.currentProvider)
// Acccounts always exposed
web3.eth.sendTransaction({/* ... */})
}
// Non-dapp browsers...
else {
console.log('Non-Ethereum browser detected. You should consider trying MetaMask!')
}
},

loadAccount: async () => {
App.account = web3.eth.accounts[0]
web3.eth.defaultAccount = App.account;
},

loadContract: async () => {
const todoList = await $.getJSON('TodoList.json')
App.contracts.TodoList = TruffleContract(todoList)
App.contracts.TodoList.setProvider(App.web3Provider)
App.todoList = await App.contracts.TodoList.deployed()
},

render: async () => {
if (App.loading) {
return
}

App.setLoading(true)

$('#account').html(App.account)

await App.renderTasks()

App.setLoading(false)
},

renderTasks: async () => {
const taskCount = await App.todoList.taskCount()
const $taskTemplate = $('.taskTemplate')

for (var i = 1; i <= taskCount; i++) {
const task = await App.todoList.tasks(i)
const taskId = task[0].toNumber()
const taskContent = task[1]
const taskCompleted = task[2]

const $newTaskTemplate = $taskTemplate.clone()
$newTaskTemplate.find('.content').html(taskContent)
$newTaskTemplate.find('input')
.prop('name', taskId)
.prop('checked', taskCompleted)
.on('click', App.toggleCompleted)

if (taskCompleted) {
$('#completedTaskList').append($newTaskTemplate)
} else {
$('#taskList').append($newTaskTemplate)
}

$newTaskTemplate.show()
}
},

createTask: async () => {
App.setLoading(true)
const content = $('#newTask').val()
await App.todoList.createTask(content)
window.location.reload()
},

toggleCompleted: async (e) => {
App.setLoading(true)
const taskId = e.target.name
await App.todoList.toggleCompleted(taskId)
window.location.reload()
},

setLoading: (boolean) => {
App.loading = boolean
const loader = $('#loader')
const content = $('#content')
if (boolean) {
loader.show()
content.hide()
} else {
loader.hide()
content.show()
}
}
}

$(() => {
$(window).load(() => {
App.load()
})
})

啟動介面。

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npm run dev

撰寫測試

新增 test/TodoList.test.js 檔。

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const { assert } = require("chai")

const TodoList = artifacts.require('./TodoList.sol')

contract('TodoList', (accounts) => {
before(async () => {
this.todoList = await TodoList.deployed()
})

it('deploys successfully', async () => {
const address = this.todoList.address
assert.notEqual(address, 0x0)
assert.notEqual(address, '')
assert.notEqual(address, null)
assert.notEqual(address, undefined)
})

it('lists tasks', async () => {
const taskCount = await this.todoList.taskCount()
const task = await this.todoList.tasks(taskCount)
assert.equal(task.id.toNumber(), taskCount.toNumber())
assert.equal(task.content, 'Check out https://github.com/memochou1993')
assert.equal(task.completed, false)
assert.equal(taskCount.toNumber(), 1)
})

it('creates tasks', async () => {
const result = await this.todoList.createTask('A new task')
const taskCount = await this.todoList.taskCount()
assert.equal(taskCount.toNumber(), 2)
const event = result.logs[0].args
assert.equal(event.id.toNumber(), 2)
assert.equal(event.content, 'A new task')
assert.equal(event.completed, false)
})

it('toggles task completion', async () => {
const result = await this.todoList.toggleCompleted(1)
const task = await this.todoList.tasks(1)
assert.equal(task.completed, true)
const event = result.logs[0].args
assert.equal(event.id.toNumber(), 1)
assert.equal(event.completed, true)
})
})

執行測試。

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truffle test

參考資料