使用solidity开发以太坊智能合约

blockchain › ethereum › HOW-TO
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一些开发合约相关资料

环境搭建（MAC）

安装solidity

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brew install solidity

安装truffle

truffle是集成安装、部署、测试合约为一体的开发框架；如果没有node环境需要先安装node:brew install node

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npm install truffle -g

合约开发

初始化项目路径

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truffle init

初始化npm环境

在初始化的过程中会让你输入一些参数的值，可以一路按回车全部使用默认值即可

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npm init

安装npm依赖库

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npm install dotenv truffle-wallet-provider ethereumjs-wallet

配置网络

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module.exports = {
  networks: {
    localnode: {
      network_id: "*",
      host: "localhost",
      port: "8545"
    }
  },

  mocha: {
    // timeout: 100000
  },

  compilers: {
    solc: {
      version: "0.8.0+commit.c7dfd78e",    // Fetch exact version from solc-bin (default: truffle's version)
    }
  },

  db: {
    enabled: false
  }
};

开发合约

按照《精通以太坊》书本的例子写了一个“水龙头”的合约，只有两个函数，一个提取以太币（withdraw），一个接收以太币（receive）。合约的代码放在项目的contracts目录下。

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// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.7.0 <0.8.0;

// my first contract
contract Faucet {

    // Give out ether to anyone who asks
    function withdraw(uint withdraw_amount) public {
        // limit withdrawal amount
        require(withdraw_amount <= 1 * 1000 * 1000 * 1000 * 1000);

        msg.sender.transfer(withdraw_amount);
    }

    // Accept any incoming amount 一个默认的函数
    // fallback () external payable {}

    // 推荐使用receive()函数来接收以太币
    receive() external payable{}

}

编译合约

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truffle compile

部署合约

参考migrations/1_initial_migration.js文件，新建一个``migrations/2_initial_migration.js；(*注意：2_initial_migration.js这个名字不能以0`开头，否则部署的时候会忽略。。。*)修改文件内容如下：

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

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

然后部署到本地的测试网络（要在本地启动truffle的ethereum测试网络）：

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truffle migrate --network localnode

执行完成之后的日志如下：

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(base) w:Faucet apple$ truffle migrate --network localnode

Compiling your contracts...
===========================
> Compiling ./contracts/Faucet.sol
> Artifacts written to /Users/apple/code/open-source/my-projects/etherum/Faucet/build/contracts
> Compiled successfully using:
   - solc: 0.8.0+commit.c7dfd78e.Emscripten.clang



Starting migrations...
======================
> Network name:    'localnode'
> Network id:      1337
> Block gas limit: 6721975 (0x6691b7)


1_initial_migration.js
======================

   Replacing 'Migrations'
   ----------------------
   > transaction hash:    0xaf813946c7470d83c7fb1e8b535efebcfdd90540c72ee9092ae9e04775bf56bc
   > Blocks: 0            Seconds: 0
   > contract address:    0x4445151f84Fd5E71aB93f0d9A1AC93fd7a454c10
   > block number:        1
   > block timestamp:     1615445677
   > account:             0xc0F680767D4Ae17C7adaF8C6d0b4805Bc207805e
   > balance:             99.99511424
   > gas used:            244288 (0x3ba40)
   > gas price:           20 gwei
   > value sent:          0 ETH
   > total cost:          0.00488576 ETH


   > Saving migration to chain.
   > Saving artifacts
   -------------------------------------
   > Total cost:          0.00488576 ETH


2_initial_migration.js
======================

   Replacing 'Faucet'
   ------------------
   > transaction hash:    0xcb451bc9f9347fa9983e5182ccc4453f1a3c7ac74b5c7785679913a7325f7715
   > Blocks: 0            Seconds: 0
   > contract address:    0x6B7d6480BC95EF2C51d2Ae247bDd2aC3bBA5690c
   > block number:        3
   > block timestamp:     1615445677
   > account:             0xc0F680767D4Ae17C7adaF8C6d0b4805Bc207805e
   > balance:             99.9888339
   > gas used:            271504 (0x42490)
   > gas price:           20 gwei
   > value sent:          0 ETH
   > total cost:          0.00543008 ETH


   > Saving migration to chain.
   > Saving artifacts
   -------------------------------------
   > Total cost:          0.00543008 ETH


Summary
=======
> Total deployments:   2
> Final cost:          0.01031584 ETH


使用truffle部署智能合约到ropsten测试网络

可以在https://infura.io/网站建立账号，可以把它看成一个geth节点，然后他提供了rpc接口。

首次执行部署，报错说HDWalletProvider没有定义

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$ truffle migrate --network ropsten

Compiling your contracts...
===========================
> Compiling ./contracts/GZToken.sol
> Compiling ./contracts/Token2.sol
> Compiling ./contracts/Token3.sol
> Artifacts written to /Users/apple/code/open-source/my-projects/etherum/Faucet/build/contracts
> Compiled successfully using:
   - solc: 0.8.0+commit.c7dfd78e.Emscripten.clang

ReferenceError: HDWalletProvider is not defined
    at Object.provider (/Users/apple/code/open-source/my-projects/etherum/Faucet/truffle-config.js:62:21)
    at Object.getProvider (/usr/local/lib/node_modules/truffle/build/webpack:/packages/provider/index.js:20:1)
    at Object.create (/usr/local/lib/node_modules/truffle/build/webpack:/packages/provider/index.js:13:1)
    at TruffleConfig.get [as provider] (/usr/local/lib/node_modules/truffle/build/webpack:/packages/config/dist/configDefaults.js:204:1)
    at Object.detect (/usr/local/lib/node_modules/truffle/build/webpack:/packages/environment/environment.js:19:1)
    at Object.run (/usr/local/lib/node_modules/truffle/build/webpack:/packages/core/lib/commands/migrate.js:206:1)
    at Command.run (/usr/local/lib/node_modules/truffle/build/webpack:/packages/core/lib/command.js:136:1)
Truffle v5.2.3 (core: 5.2.3)
Node v14.16.0

解决方案：

添加依赖：
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npm install truffle-hdwallet-provider
npm install dotenv
在与truffle-config.js相同的目录下添加.evn文件，然后写入你的助记词，如：
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mnemonic=topic foster find apple famous have bonus month remain middle funny smart

注意在gitignore文件中把这个文件（.evn）忽略，避免上传到github

修改truffle-config.js：在最上面添加：
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// 在使用infura作为rpc-api的提供方时，因为infura不管理我们的私钥所以要在本地有一个钱包用于签名
var HDWalletProvider = require("truffle-hdwallet-provider");
// 默认读取项目根目录下的.env文件,用process.env.调用
const result = require('dotenv').config();
if (result.error) {
  throw result.error;
}

修改ropsten的配置如下：
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ropsten: {
      provider: () => new HDWalletProvider(process.env.mnemonic, `https://ropsten.infura.io/v3/your-id`),
      network_id: 3,       // Ropsten's id
      gas: 5500000,        // Ropsten has a lower block limit than mainnet
      confirmations: 2,    // # of confs to wait between deployments. (default: 0)
      timeoutBlocks: 200,  // # of blocks before a deployment times out  (minimum/default: 50)
      skipDryRun: true     // Skip dry run before migrations? (default: false for public nets )
    },

重新部署：

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$truffle migrate --network ropsten

Compiling your contracts...
===========================
> Compiling ./contracts/GZToken.sol
> Compiling ./contracts/Token3.sol
> Artifacts written to /Users/apple/code/open-source/my-projects/etherum/Faucet/build/contracts
> Compiled successfully using:
   - solc: 0.8.0+commit.c7dfd78e.Emscripten.clang



Starting migrations...
======================
> Network name:    'ropsten'
> Network id:      3
> Block gas limit: 8000000 (0x7a1200)


1_initial_migration.js
======================

   Deploying 'Migrations'
   ----------------------

Error:  *** Deployment Failed ***

"Migrations" -- insufficient funds for gas * price + value.

    at /usr/local/lib/node_modules/truffle/build/webpack:/packages/deployer/src/deployment.js:365:1
    at processTicksAndRejections (internal/process/task_queues.js:93:5)
    at Migration._deploy (/usr/local/lib/node_modules/truffle/build/webpack:/packages/migrate/Migration.js:74:1)
    at Migration._load (/usr/local/lib/node_modules/truffle/build/webpack:/packages/migrate/Migration.js:61:1)
    at Migration.run (/usr/local/lib/node_modules/truffle/build/webpack:/packages/migrate/Migration.js:212:1)
    at Object.runMigrations (/usr/local/lib/node_modules/truffle/build/webpack:/packages/migrate/index.js:150:1)
    at Object.runFrom (/usr/local/lib/node_modules/truffle/build/webpack:/packages/migrate/index.js:110:1)
    at Object.run (/usr/local/lib/node_modules/truffle/build/webpack:/packages/migrate/index.js:87:1)
    at runMigrations (/usr/local/lib/node_modules/truffle/build/webpack:/packages/core/lib/commands/migrate.js:263:1)
    at Object.run (/usr/local/lib/node_modules/truffle/build/webpack:/packages/core/lib/commands/migrate.js:228:1)
    at Command.run (/usr/local/lib/node_modules/truffle/build/webpack:/packages/core/lib/command.js:136:1)
Truffle v5.2.3 (core: 5.2.3)
Node v14.16.0

原因是没有足够的汽油费，去https://faucet.ropsten.be/获取即可。

在此重新部署：

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$ truffle migrate --network ropsten

Compiling your contracts...
===========================
> Compiling ./contracts/Token3.sol
> Artifacts written to /Users/apple/code/open-source/my-projects/etherum/Faucet/build/contracts
> Compiled successfully using:
   - solc: 0.8.0+commit.c7dfd78e.Emscripten.clang



Starting migrations...
======================
> Network name:    'ropsten'
> Network id:      3
> Block gas limit: 8000000 (0x7a1200)


1_initial_migration.js
======================

   Deploying 'Migrations'
   ----------------------
   > transaction hash:    0x212e4eee81d5fc3024db8d6787b36a51f070f832b94961605de18675d8f597d3
   > Blocks: 2            Seconds: 13
   > contract address:    0x0d4f7ff83b66e1E3377aacE5EFA70d9E036890c2
   > block number:        9941219
   > block timestamp:     1617088554
   > account:             0x2560be5793F9AA00963e163A1287807Feb897e2F
   > balance:             0.99508824
   > gas used:            245588 (0x3bf54)
   > gas price:           20 gwei
   > value sent:          0 ETH
   > total cost:          0.00491176 ETH

   Pausing for 2 confirmations...
   ------------------------------
   > confirmation number: 2 (block: 9941221)

   > Saving migration to chain.
   > Saving artifacts
   -------------------------------------
   > Total cost:          0.00491176 ETH


2_initial_migration.js
======================

   Deploying 'Faucet'
   ------------------
   > transaction hash:    0x40ead4c9b0fa1efb90d551e43587c10457e0c99deeaf4f804222645395435090
   > Blocks: 2            Seconds: 21
   > contract address:    0xE18C40cEf01bEedA140033892b4638CFBc464BbD
   > block number:        9941227
   > block timestamp:     1617088603
   > account:             0x2560be5793F9AA00963e163A1287807Feb897e2F
   > balance:             0.9887139
   > gas used:            272804 (0x429a4)
   > gas price:           20 gwei
   > value sent:          0 ETH
   > total cost:          0.00545608 ETH

   Pausing for 2 confirmations...
   ------------------------------
   > confirmation number: 1 (block: 9941229)
   > confirmation number: 2 (block: 9941230)

   > Saving migration to chain.
   > Saving artifacts
   -------------------------------------
   > Total cost:          0.00545608 ETH


3_initial_migration.js
======================

   Deploying 'GZToken'
   -------------------
   > transaction hash:    0xf28b9b32e6cbf0b12a44249dd4c6eb914706820daafc671e43cabb4541d5396b
   > Blocks: 2            Seconds: 25
   > contract address:    0xB8DfEe0D9aC703E75EE3D031148227B3BbB26524
   > block number:        9941234
   > block timestamp:     1617088662
   > account:             0x2560be5793F9AA00963e163A1287807Feb897e2F
   > balance:             0.9713052
   > gas used:            841622 (0xcd796)
   > gas price:           20 gwei
   > value sent:          0 ETH
   > total cost:          0.01683244 ETH

   Pausing for 2 confirmations...
   ------------------------------
   > confirmation number: 1 (block: 9941235)
   > confirmation number: 2 (block: 9941236)

   > Saving migration to chain.
   > Saving artifacts
   -------------------------------------
   > Total cost:          0.01683244 ETH


Summary
=======
> Total deployments:   3
> Final cost:          0.02720028 ETH

调用合约的报错汇总：

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Received unexpected error:
        	            	out of gas
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intrinsic gas too low: have 0, want 21420 (supplied gas 0)

上面这些全部都是因为gas费设置的太少导致的。

与合约交互

在remix中调用合约

在remix网页中部署完成合约之后，在下面可以看到withdraw函数，输入提现的金额然后点击transact按钮，就可以调起MetaMask调用智能合约。

image-20210309173249673

使用truffle的命令调用合约

启动truffle的console控制台：
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truffle console --network localnode
打开之后双击两次tab键会有命令提示，我们查看一下部署的Faucet合约的地址：
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truffle(localnode)> Faucet.address
'0x6B7d6480BC95EF2C51d2Ae247bDd2aC3bBA5690c'
查看我们合约的账户余额：
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truffle(localnode)> web3.eth.getBalance(Faucet.address)
'0'

truffle develop

develop Open a console with a local development blockchain

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truffle(develop)> Faucet.deployed().then(i => {FaucetDeployed = i})
// 发送给合约1个eth
truffle(develop)> FaucetDeployed.send(web3.utils.toWei("1", "ether")).then(res => { console.log(res.logs[0].event, res.logs[0].args) })
Deposit Result {
  '0': '0xAC3509D2d2746B6fEC873087AAB9394d03472131',
  '1': BN {
    negative: 0,
    words: [ 56885248, 2993385, 222, <1 empty item> ],
    length: 3,
    red: null
  },
  __length__: 2,
  to: '0xAC3509D2d2746B6fEC873087AAB9394d03472131',
  amount: BN {
    negative: 0,
    words: [ 56885248, 2993385, 222, <1 empty item> ],
    length: 3,
    red: null
  }
}
// 从合约提取0.1eth
truffle(develop)> FaucetDeployed.withdraw(web3.utils.toWei("0.1", "ether")).then(res => { console.log(res.logs[0].event, res.logs[0].args) })
Withdrawal Result {
  '0': '0xAC3509D2d2746B6fEC873087AAB9394d03472131',
  '1': BN {
    negative: 0,
    words: [ 25821184, 13721111, 22, <1 empty item> ],
    length: 3,
    red: null
  },
  __length__: 2,
  to: '0xAC3509D2d2746B6fEC873087AAB9394d03472131',
  amount: BN {
    negative: 0,
    words: [ 25821184, 13721111, 22, <1 empty item> ],
    length: 3,
    red: null
  }
}

与Gas费相关的注意事项

如果在执行过程中gas费耗尽，会触发如下一系列事件：

  • 抛出“out of gas”异常
  • 状态被恢复到执行开始之前
  • 所有在这次执行过程中的gas开销都会被作为交易费用，以太坊不会因为交易中止而退回gas或以太币。

如何把合约函数调用的gas费消耗最小化

避免动态尺寸的数组

例如对数组的每个元素进行操作，或者通过遍历的方式查找数组中的某个值。

避免调用其他合约

调用其他合约，特别是那些gas消耗未知的合约，可能会产生高昂的gas开销。

估计gas开销