智能合约实战 - FurnaceCoin

本示例用于展示如何基于ERC20标准代币，实现一套自己的代币。

1. 创建项目和设置配置信息

1.1 创建项目 FurnaceCoin

mkdir FurnaceCoin
cd FurnaceCoin

1.2 配置truffle信息

truffle init

在生成的文件truffle.js配置以太坊网络等信息。

1.3 配置nodejs信息

npm init

在生成的文件package.json中配置依赖的npm包。

2. 编写智能合约

2.1 编写智能合约 FurnaceCoin

编写智能合约 contracts/FurnaceCoin.sol，实现自己的代币。

示例如下：

pragma solidity ^0.4.23;

import "../node_modules/zeppelin-solidity/contracts/ownership/Ownable.sol";
import "../node_modules/zeppelin-solidity/contracts/token/ERC20/StandardToken.sol";

contract FurnaceCoin is Ownable, StandardToken {
    string public name = "FurnaceCoin";
    string public symbol = "FCoin";
    uint public decimals = 18;
    uint public INITIAL_SUPPLY = 1000000000;

    constructor(uint _initSupply) public {
        if (_initSupply <= 0)
            _initSupply = INITIAL_SUPPLY;

        totalSupply_ = _initSupply;

        balances[msg.sender] = totalSupply_;

        emit Transfer(address(0x0), msg.sender, totalSupply_);
    }

    function mint(uint _value) public onlyOwner returns(bool) {
        totalSupply_ += _value;

        balances[msg.sender] += _value;

        emit Transfer(address(0x0), msg.sender, _value);
    }
}

这里用到了 zeppelin-solidity 库中的 ERC20 标准代币实现。

FurnaceCoin 在创建时便设定初始代币数量，并全部分配给创建者。
同时支持创建者在后续增加代币的总数量，通过方法 mint() 实现。

3. 部署智能合约

3.1 编写部署脚本

编写部署脚本 migrations/2_deploy_contracts.js。

示例如下：

var FurnaceCoin = artifacts.require("./FurnaceCoin.sol");

module.exports = function(deployer) {
    var initSupply = 3000000000;
    
    deployer.deploy(FurnaceCoin, initSupply);
};

3.2 将智能合约部署到以太坊网络

truffle migrate --network ganache

这里，需要记住各智能合约在指定以太坊网络中的合约地址。

4. 使用 FurnaceCoin

这里只通过 nodejs 脚本来使用 FurnaceCoin，存放于目录 scripts。

4.1 转账操作

脚本 scripts/transfer.js 用于实现转账操作。

var Web3 = require('web3');
var contract = require('truffle-contract');

//var rpcUrl = "http://localhost:7545";
var rpcUrl = "http://192.168.60.12:7545";

const provider = new Web3.providers.HttpProvider(rpcUrl);
const web3 = new Web3(provider);

const FurnaceCoin = contract(require('../build/contracts/FurnaceCoin.json'));
FurnaceCoin.setProvider(provider);

const showError = error => {
    console.error(error);
};

var addressOfFurnaceCoin = "0xbefd2d3f950f0e948bd0bef1f03f84636185c09c";
var deployed = FurnaceCoin.at(addressOfFurnaceCoin);

var accounts = web3.eth.accounts;
var acc0, balanceOfAcc0;
var acc1, balanceOfAcc1;
var acc2, balanceOfAcc2;
var acc3, balanceOfAcc3;
var acc4, balanceOfAcc4;

if (accounts.length > 0)
    acc0 = web3.eth.accounts[0];

if (accounts.length > 1)
    acc1 = web3.eth.accounts[1];

if (accounts.length > 2)
    acc2 = web3.eth.accounts[2];

if (accounts.length > 3)
    acc3 = web3.eth.accounts[3];

if (accounts.length > 4)
    acc4 = web3.eth.accounts[4];

var async_func_transfer = async function(to, value, sender) {
    var result = await deployed.transfer(to, value, {from: sender});
    console.log("\nTest transfer (sender:", sender, ", to:", to, ", value:", value, ").");
    console.log("transfer tx: ", result.tx);
}

async_func_transfer(acc1, 1000, acc0);

4.2 监听事件

创建脚本 scripts/events.js 用于监听 FurnaceCoin 触发的日志。

scripts/events.js

var Web3 = require('web3');
var contract = require('truffle-contract');

//var rpcUrl = "http://localhost:7545";
var rpcUrl = "http://192.168.60.12:7545";

const provider = new Web3.providers.HttpProvider(rpcUrl);
const web3 = new Web3(provider);

const FurnaceCoin = contract(require('../build/contracts/FurnaceCoin.json'));
FurnaceCoin.setProvider(provider);

const showError = error => {
    console.error(error);
};

var addressOfFurnaceCoin = "0xbefd2d3f950f0e948bd0bef1f03f84636185c09c";
var deployed = FurnaceCoin.at(addressOfFurnaceCoin);

console.log("Event Lister.");

var eventTransfer = deployed.Transfer();
var eventApproval = deployed.Approval();

eventTransfer.watch(function(error, result){
    if (error) {
        console.error(error);
        return;
    }
    
    console.log('\nEvent for Transfer:');
    console.log('transactionIndex: ', result.transactionIndex);
    console.log('transactionHash: ', result.transactionHash);
    console.log('blockHash: ', result.blockHash);
    console.log('blockNumber: ', result.blockNumber);
    console.log('addressOfFurnaceCoin: ', result.address);
    console.log('from: ', result.args.from);
    console.log('to: ', result.args.to);
    console.log('value: ', result.args.value.toNumber());
});

eventApproval.watch(function(error, result){
    if (error) {
        console.error(error);
        return;
    }
    
    console.log('\nEvent for Approval:');
    console.log('transactionIndex: ', result.transactionIndex);
    console.log('transactionHash: ', result.transactionHash);
    console.log('blockHash: ', result.blockHash);
    console.log('blockNumber: ', result.blockNumber);
    console.log('addressOfFurnaceCoin: ', result.address);
    console.log('owner: ', result.args.owner);
    console.log('spender: ', result.args.spender);
    console.log('value: ', result.args.value.toNumber());
});

4.3 使用 FurnaceCoin

创建脚本 scritps/test.js，调用 FurnaceCoin 中的方法。

主要是：

对于每个字段，调用同名的获取方法，查看对应值。
通过方法 totalSupply() 查看总的代币数量。
通过方法 balanceOf() 查询给定账户的代币余额。
通过方法 transfer() 转账指定数量的代币给指定账户。
通过方法 approve() 授权指定数量的代币可由指定账户进行支付。
通过方法 allowance() 查询授权支付信息。
通过方法 increaseApproval() 追加支付授权。
通过方法 decreaseApproval() 撤销指定数量的支付授权。
通过方法 transferFrom() 进行授权支付。

特别需要注意的是，当调用方法 transfer(), transferFrom() 时会触发事件 Transfer。
当调用方法 approve(), increaseApproval(), decreaseApproval() 时会触发事件 Approval。
启动脚本 scripts/events.js 将能够监听到这些日志事件，并输出日志的详细信息。

var Web3 = require('web3');
var contract = require('truffle-contract');

//var rpcUrl = "http://localhost:7545";
var rpcUrl = "http://192.168.60.12:7545";

const provider = new Web3.providers.HttpProvider(rpcUrl);
const web3 = new Web3(provider);

const FurnaceCoin = contract(require('../build/contracts/FurnaceCoin.json'));
FurnaceCoin.setProvider(provider);

const showError = error => {
    console.error(error);
};

var addressOfFurnaceCoin = "0xbefd2d3f950f0e948bd0bef1f03f84636185c09c";
var deployed = FurnaceCoin.at(addressOfFurnaceCoin);

var accounts = web3.eth.accounts;
var acc0, balanceOfAcc0;
var acc1, balanceOfAcc1;
var acc2, balanceOfAcc2;
var acc3, balanceOfAcc3;
var acc4, balanceOfAcc4;

if (accounts.length > 0)
    acc0 = web3.eth.accounts[0];

if (accounts.length > 1)
    acc1 = web3.eth.accounts[1];

if (accounts.length > 2)
    acc2 = web3.eth.accounts[2];

if (accounts.length > 3)
    acc3 = web3.eth.accounts[3];

if (accounts.length > 4)
    acc4 = web3.eth.accounts[4];

console.log("Test FurnaceCoin.");
deployed.then(function() {
    return deployed.name();
})
.then(function(result) {
    console.log("\nTest name:");
    console.log("name: ", result);

    return deployed.symbol();
})
.then(function(result) {
    console.log("\nTest symbol:");
    console.log("symbol: ", result);

    return deployed.decimals();
})
.then(function(result) {
    console.log("\nTest decimals:");
    console.log("decimals: ", result.toNumber());

    return deployed.INITIAL_SUPPLY();
})
.then(function(result) {
    console.log("\nTest INITIAL_SUPPLY:");
    console.log("INITIAL_SUPPLY: ", result.toNumber());

    return deployed.totalSupply();
})
.then(function(result) {
    console.log("\nTest totalSupply_:");
    console.log("totalSupply_: ", result.toNumber());

    return deployed.balanceOf(acc0);
})
.then(function(result) {
    console.log("\nTest balanceOfAcc0:");
    console.log("balanceOfAcc0: ", result.toNumber());

    balanceOfAcc0 = result.toNumber();

    return deployed.balanceOf(acc1);
})
.then(function(result) {
    console.log("\nTest balanceOfAcc1:");
    console.log("balanceOfAcc1: ", result.toNumber());

    balanceOfAcc1 = result.toNumber();

    return deployed.transfer(acc1, 1000, {from: acc0});
})
.then(function(result) {
    console.log("\nTest transfer:");
    console.log("transfer tx: ", result.tx);

    return deployed.balanceOf(acc0);
})
.then(function(result) {
    console.log("\nTest balanceOfAcc0:");
    console.log("balanceOfAcc0: ", result.toNumber());

    balanceOfAcc0 = result.toNumber();

    return deployed.balanceOf(acc1);
})
.then(function(result) {
    console.log("\nTest balanceOfAcc1:");
    console.log("balanceOfAcc1: ", result.toNumber());

    balanceOfAcc1 = result.toNumber();

    return deployed.approve(acc0, 3000, {from: acc0});
})
.then(function(result) {
    console.log("\nTest approve:");
    console.log("approve tx: ", result.tx);

    return deployed.allowance(acc0, acc0);
})
.then(function(result) {
    console.log("\nTest allowance:");
    console.log("allowance: ", result.toNumber());

    return deployed.increaseApproval(acc0, 1000, {from: acc0});
})
.then(function(result) {
    console.log("\nTest increaseApproval:");
    console.log("increaseApproval tx: ", result.tx);

    return deployed.allowance(acc0, acc0);
})
.then(function(result) {
    console.log("\nTest allowance:");
    console.log("allowance: ", result.toNumber());

    return deployed.decreaseApproval(acc0, 500, {from: acc0});
})
.then(function(result) {
    console.log("\nTest decreaseApproval:");
    console.log("decreaseApproval tx: ", result.tx);

    return deployed.allowance(acc0, acc0);
})
.then(function(result) {
    console.log("\nTest allowance:");
    console.log("allowance: ", result.toNumber());

    return deployed.transferFrom(acc0, acc1, 1000, {from: acc0});
})
.then(function(result) {
    console.log("\nTest transferFrom:");
    console.log("transferFrom tx: ", result.tx);

    return deployed.balanceOf(acc0);
})
.then(function(result) {
    console.log("\nTest balanceOfAcc0:");
    console.log("balanceOfAcc0: ", result.toNumber());

    balanceOfAcc0 = result.toNumber();

    return deployed.balanceOf(acc1);
})
.then(function(result) {
    console.log("\nTest balanceOfAcc1:");
    console.log("balanceOfAcc1: ", result.toNumber());

    balanceOfAcc1 = result.toNumber();
})
.catch(showError);

项目源代码

项目源代码已逐步上传到 Github，地址为 https://github.com/windstamp/dapp/tree/master/examples/FurnaceCoin。

Contributor

Windstamp, https://github.com/windstamp

5.2 智能合约实战 - FurnaceCoin