如何编写智能合约(Smart Contract)（I）最新

素颜马尾好姑娘i 2022-05-19 12:54 237阅读 0赞

# #

## **写在前面** ##

参考原文:[http://liyuechun.org/2017/09/19/how-to-code-smart-contract/][http_liyuechun.org_2017_09_19_how-to-code-smart-contract]有版本问题,按照原文会出错

最新:

[https://truffleframework.com/docs/advanced/configuration\#resolving-naming-conflicts-on-windows][https_truffleframework.com_docs_advanced_configuration_resolving-naming-conflicts-on-windows]

Window用户请参看上文,作者写这篇文章的时候,在使用truffle命令时,除了使用  
truffle int之外,truffle 都要加.cmd即truffle.cmd  
或者另一种做法是把truffle.js名字换掉.  
truffle.js需配置  
module.exports = \{

networks: \{

development: \{

host: "127.0.0.1",

port: 8545,//端口

network\_id: "\*" // Match any network id

\}\};

## 学习目标 ##

1.  了解智能合约
2.  简单环境搭建
3.  能够利用`solidity`编写`Hello World`合约
4.  合约部署
5.  和合约互动

## 使用solidity语言撰写智能合约 ##

`Ethereum`上的智能合约需要使用`solidity`语言来撰写。虽然还有其他能用来撰写智能合约的语言如`Serpent`（类Python）、`lll`（类Fortran），但目前看到所有公开的智能合约都是使用`solidity`撰写。

宣传上说，`solidity`是一种类似`Javascript`的语言，而且围绕着`solidity`的各种开发工具链，都是使用属于`Javascript`生态系的`npm`来提供的。但我觉得`solidity`还是比较像Java或C\#。因为和Javascript不同，solidity与Java或C\#同属于强类型（Strong Type，在定义变数时需要指定类型）语言、在定义函式（function）时同样需指定回传的类型（type）、同样也需要先编译才能执行。这些特性都是`Javascript`所不具备的。

## 开发前的准备 ##

本文将使用当前最活跃的智能合约开发框架`truffle`为基础来开发。`ENS（Ethereum Name Service）`也是采用`truffle`框架。其他选择还有`embark`等。

就像一般网站或App开发一样，在提供公开服务之前，开发者会在自己用于写程序的电脑（又称作本机）或透过测试网络来测试程序执行的效果，测试完成后，才会部署到公开的网络上提供服务。开发区块链智能合约（程序）的过程也是如此。特别是公开链上所有写入或读取计算结果的操作都需要真金白银（虚拟代币），而且根据网络状况，每个公开链上的操作都需要要一小段反应时间（15秒~数分钟），这些等待颇浪费宝贵的开发时间⏳。因此在开发的过程中，我们将使用`testrpc`工具在电脑上模拟智能合约所需的以太坊内存块链测试环境。

`testrpc`中也包含了`Javascript`版本的`Ethereum`虚拟机（Ethereum Virtual Machine），因此可以完整地执行智能合约。

此外，开发前还需准备一个合手的编辑器。我目前是使用vscode搭配`solidity`插件来开发。`solidity`插件除了支持语法高亮之外，也会透过`Solium`检查并提示基本的语法错误，相当方便。其他编辑器应该也有类似的插件可选择。

![Snip20170919_6.png][]![Snip20170919_7.png][]![Snip20170919_8.png][]

## 安装所需工具 ##

首先开发机上必须装好Node.js，再使用以下命令安装所需的工具：

$ npm install -g ethereumjs-testrpc truffle

liyuechun:~ yuechunli$ npm install -g ethereumjs-testrpc truffle
    /usr/local/bin/testrpc -> /usr/local/lib/node_modules/ethereumjs-testrpc/build/cli.node.js
    /usr/local/bin/truffle -> /usr/local/lib/node_modules/truffle/build/cli.bundled.js
    + truffle@3.4.9
    + ethereumjs-testrpc@4.1.3
    added 1 package and updated 7 packages in 76.132s
    liyuechun:~ yuechunli$

## 启动Testrpc ##

安装好后随时可以使用`testrpc`命令来启动以太坊测试环境。

liyuechun:~ yuechunli$ testrpc
    EthereumJS TestRPC v4.1.3 (ganache-core: 1.1.3)
    
    Available Accounts
    ==================
    (0) 0xbbd414b340f2255dab9d923428c97f0b65d9df81
    (1) 0xe9869e3cf29b6fca81762c314df229c7c4fea25e
    (2) 0xc79e72362a4511b9e499d186654332c4d6f569be
    (3) 0x9a6f0651907c149d4173c03927144dbbba1473d4
    (4) 0x5b13a5d6788752b26dd4e338aae2e01058ee145e
    (5) 0xfc7f56d942ad5260be23ecee92a344aba1b7e7d8
    (6) 0xc48dc22c6bacd6ade4421ab54f25bc45c1c51142
    (7) 0x3fe2b7d4141dd0a456661f77086d055cbaf3b78f
    (8) 0x567979fed26ca85e9d1b4ac919c840e3fc9857e2
    (9) 0xb2eafe245f098eef1c2c1f466d9a8dcd58764c62
    
    Private Keys
    ==================
    (0) 947ab78e91133103612ca099d60e6c38cac5bb769f7f097c82d003cf058500bd
    (1) 8ffe0ba8dc53e16944a17dddd3378b5fba0379cd84df4e5237b8b46d05b8762f
    (2) ffe2e04e43e4106b247407656f5233bcc3e0c49730972d0df9c1d1093375e2ef
    (3) a20e453dc44c76aaca6a22efdbb605c2ed9eea64c11317e683461e11bd105ea7
    (4) 4748268ff1b828868dc56d07a1b121b427e1bdede5dbb3c14ef1254d9d26b1a5
    (5) f9957e68c6d20d38b81604a0509e6c4591478bc754f87d5682564073705fbb46
    (6) 34e648b23c0ace6b2b0893651d87f70be8496f97ecf6b7b4607b2acc4e05c9bd
    (7) d2477cedec217e3fb19a5981dafbc125ef66ccc9dc7df29301d08a24da843cf5
    (8) d319f85ccd80e55b2e707e05f09662632564c297248f8b96f82ea5eeaeef0851
    (9) 88c33ac9f1062b82f9e82f86a0ce307e3bd8fcf683b9751232c2f193f5bdc668
    
    HD Wallet
    ==================
    Mnemonic:      hire custom clinic expect fury fantasy try dress source spy viable flag
    Base HD Path:  m/44'/60'/0'/0/{account_index}
    
    Listening on localhost:8545

可以看到`testrpc`启动后自动建立了`10`个帐号（Accounts），与每个帐号对应的私钥（Private Key）。每个帐号中都有`100`个测试用的以太币（Ether）。要注意`testrpc`仅运行在內存中，因此每次重开时都会回到全新的状态。

一切准备就绪，我们可以开始建立第一份智能合约项目了。

## 建立项目 ##

开启另一个终端窗口，输入以下命令以建立项目：

liyuechun:Desktop yuechunli$ mkdir SmartContractDemo
    liyuechun:Desktop yuechunli$ cd SmartContractDemo/
    liyuechun:SmartContractDemo yuechunli$ mkdir HelloWorld
    liyuechun:SmartContractDemo yuechunli$ cd HelloWorld/
    liyuechun:HelloWorld yuechunli$ truffle init
    
    Downloading project...
    Project initialized.
    
      Documentation: http://truffleframework.com/docs
    
    Commands:
    
      Compile: truffle compile
      Migrate: truffle migrate
      Test:    truffle test
    
    liyuechun:HelloWorld yuechunli$ ls
    contracts	migrations	test		truffle.js

目录结构：

`/contracts:`存放智能合约原始代码的地方，可以看到里面已经有三个`sol`文件，我们开发的`HelloWorld.sol`文件就存放在这里。

`/migrations:`这是 `Truffle`用来部署智能合约的功能，待会儿我们会修改`2_deploy_contracts.js`来部署 `HelloWorld.sol`。 `/test: `测试智能合约的代码放在这里，支持`js` 与 `sol` 测试。 `truffle.js:` `Truffle` 的设置文档。

![Snip20170919_12.png][]

## 新建HelloWorld合约 ##

在`contracts`文件夹下新建`HelloWorld.sol`文件，当然也可以直接在`HelloWorld`路径下面直接执行`truffle create contract HelloWorld`命令来创建`HelloWorld.sol`。

![Snip20170919_13.png][]

`HelloWorld.sol`文件內容如下：

pragma solidity ^0.4.4;
    
    contract HelloWorld {
      function sayHello() returns (string) {
        return ("Hello World");
      }
    }

![Snip20170919_14.png][]

## 讲解 ##

pragma solidity ^0.4.4;

第一行指名目前使用的`solidity`版本，不同版本的`solidity`可能会编译出不同的`bytecode`。`^`代表兼容`solidity``0.4.4 ~ 0.4.9`的版本。

contract HelloWorld {
        ...
    }

`contract`关键字类似于其他语言中较常见的`class`。因为`solidity`是专为智能合约（Contact）设计的语言，声明`contract`后即内置了开发智能合约所需的功能。也可以把这句理解为`class HelloWorld extends Contract`。

function sayHello() returns (string) {
        return ("Hello World");
    }

函数的结构与其他程序类似，但如果有传入的参数或回传值，需要指定参数或回传值的类型（type）。

## 编译 ##

现在执行`truffle compile`命令，我们可以将`HelloWorld.sol`原始码编译成`Ethereum bytecode`。

liyuechun:HelloWorld yuechunli$ ls
    contracts	migrations	test		truffle.js
    liyuechun:HelloWorld yuechunli$ truffle compile
    Compiling ./contracts/ConvertLib.sol...
    Compiling ./contracts/HelloWorld.sol...
    Compiling ./contracts/MetaCoin.sol...
    Compiling ./contracts/Migrations.sol...
    Writing artifacts to ./build/contracts
    
    liyuechun:HelloWorld yuechunli$ ls
    build		contracts	migrations	test		truffle.js
    liyuechun:HelloWorld yuechunli$ cd build/
    liyuechun:build yuechunli$ ls
    contracts
    liyuechun:build yuechunli$ cd contracts/
    liyuechun:contracts yuechunli$ ls
    ConvertLib.json	HelloWorld.json	MetaCoin.json	Migrations.json
    liyuechun:contracts yuechunli$ cat HelloWorld.json 
    {
      "contract_name": "HelloWorld",
      "abi": [
        {
          "inputs": [],
          "payable": false,
          "type": "constructor"
        }
      ],
      "unlinked_binary": "0x60606040523415600e57600080fd5b5b5b5b603680601e6000396000f30060606040525b600080fd00a165627a7a723058203ee98a767948e9bc08094df4a46ab0361f068b2a559032cf968df5bbf63e91430029",
      "networks": {},
      "schema_version": "0.0.5",
      "updated_at": 1505805826302
    }
    liyuechun:contracts yuechunli$

![Snip20170919_15.png][]

编译成功后，会在`HelloWorld`文件夹下面的`build/contracts`文件夹下面看见`HelloWorld.json`文件。

## 部署 ##

`truffle`框架中提供了方便部署合约的脚本。打开`migrations/2_deploy_contracts.js`文件（脚本使用`Javascript`编写），将内容修改如下：

var HelloWorld = artifacts.require("HelloWorld");
    module.exports = function(deployer) {
      deployer.deploy(HelloWorld);
    };

![Snip20170919_17.png][]

使用`artifacts.require`语句来取得准备部署的合约。使用`deployer.deploy`语句将合约部署到区块链上。这边`HelloWorld`是`contract`的名称而不是文件名。因此可以用此语法读入任一`.sol`文件中的任一合约。

现在执行`truffle migrate`命令：

liyuechun:HelloWorld yuechunli$ ls
    build		contracts	migrations	test		truffle.js
    liyuechun:HelloWorld yuechunli$ truffle migrate
    Compiling ./contracts/HelloWorld.sol...
    Writing artifacts to ./build/contracts
    
    Using network 'development'.
    
    Running migration: 1_initial_migration.js
      Deploying Migrations...
      ... 0x218431f16a5cadc6347449808d981887c90b3872898af7cc9dc9b3280c07c184
      Migrations: 0x64e9673cf962d21642a08635e6654fb7f2ea9bcd
    Saving successful migration to network...
      ... 0xd9ec788c106df36b8491c95a0ab02ff1e5ef22c1965c910a2576e8259a00535c
    Saving artifacts...
    Running migration: 2_deploy_contracts.js
      Deploying HelloWorld...
      ... 0x17774b4914d7bc7ab2505a53c59bda6a1fce30c9839d19d735290ca9140450ea
      HelloWorld: 0x471a22ffe2bddd02e82853059871067e4c07a7f4
    Saving successful migration to network...
      ... 0xe5e2e11cf5a63ca4517221c68dadb3cae2ca42cbfed93c09c575b6d5f275fc8b
    Saving artifacts...
    liyuechun:HelloWorld yuechunli$

如此一来合约已经部署到`testrpc`中。切换到`testrpc`窗口，可以看到`testrpc`有反应了。

![Snip20170919_18.png][]

## 与合约互动 ##

`truffle`提供命令行工具，执行`truffle console`命令后，可用`Javascript`来和刚刚部署的合约互动。

liyuechun:HelloWorld yuechunli$ ls
    build		contracts	migrations	test		truffle.js
    liyuechun:HelloWorld yuechunli$ truffle console
    truffle(development)> HelloWorld.deployed().then(instance => contract = instance)
    TruffleContract {
      constructor: 
       { [Function: TruffleContract]
         _static_methods: 
          { setProvider: [Function: setProvider],
            new: [Function: new],
            at: [Function: at],
            deployed: [Function: deployed],
            defaults: [Function: defaults],
            hasNetwork: [Function: hasNetwork],
            isDeployed: [Function: isDeployed],
            detectNetwork: [Function: detectNetwork],
            setNetwork: [Function: setNetwork],
            resetAddress: [Function: resetAddress],
            link: [Function: link],
            clone: [Function: clone],
            addProp: [Function: addProp],
            toJSON: [Function: toJSON] },
         _properties: 
          { contract_name: [Object],
            abi: [Object],
            network: [Function: network],
            networks: [Function: networks],
            address: [Object],
            links: [Function: links],
            events: [Function: events],
            binary: [Function: binary],
            unlinked_binary: [Object],
            schema_version: [Function: schema_version],
            updated_at: [Function: updated_at] },
         _property_values: {},
         _json: 
          { contract_name: 'HelloWorld',
            default_network: undefined,
            abi: [Array],
            unlinked_binary: '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',
            networks: [Object],
            schema_version: '0.0.5',
            updated_at: 1505806918535 },
         setProvider: [Function: bound setProvider],
         new: [Function: bound new],
         at: [Function: bound at],
         deployed: [Function: bound deployed],
         defaults: [Function: bound defaults],
         hasNetwork: [Function: bound hasNetwork],
         isDeployed: [Function: bound isDeployed],
         detectNetwork: [Function: bound detectNetwork],
         setNetwork: [Function: bound setNetwork],
         resetAddress: [Function: bound resetAddress],
         link: [Function: bound link],
         clone: [Function: bound clone],
         addProp: [Function: bound addProp],
         toJSON: [Function: bound toJSON],
         web3: 
          Web3 {
            _requestManager: [Object],
            currentProvider: [Object],
            eth: [Object],
            db: [Object],
            shh: [Object],
            net: [Object],
            personal: [Object],
            bzz: [Object],
            settings: [Object],
            version: [Object],
            providers: [Object],
            _extend: [Object] },
         class_defaults: 
          { from: '0xbbd414b340f2255dab9d923428c97f0b65d9df81',
            gas: 4712388,
            gasPrice: 100000000000 },
         currentProvider: 
          HttpProvider {
            host: 'http://localhost:8545',
            timeout: 0,
            send: [Function],
            sendAsync: [Function],
            _alreadyWrapped: true },
         network_id: '1505794143155' },
      abi: 
       [ { constant: false,
           inputs: [],
           name: 'sayHello',
           outputs: [Array],
           payable: false,
           type: 'function' } ],
      contract: 
       Contract {
         _eth: 
          Eth {
            _requestManager: [Object],
            getBalance: [Object],
            getStorageAt: [Object],
            getCode: [Object],
            getBlock: [Object],
            getUncle: [Object],
            getCompilers: [Object],
            getBlockTransactionCount: [Object],
            getBlockUncleCount: [Object],
            getTransaction: [Object],
            getTransactionFromBlock: [Object],
            getTransactionReceipt: [Object],
            getTransactionCount: [Object],
            call: [Object],
            estimateGas: [Object],
            sendRawTransaction: [Object],
            signTransaction: [Object],
            sendTransaction: [Object],
            sign: [Object],
            compile: [Object],
            submitWork: [Object],
            getWork: [Object],
            coinbase: [Getter],
            getCoinbase: [Object],
            mining: [Getter],
            getMining: [Object],
            hashrate: [Getter],
            getHashrate: [Object],
            syncing: [Getter],
            getSyncing: [Object],
            gasPrice: [Getter],
            getGasPrice: [Object],
            accounts: [Getter],
            getAccounts: [Object],
            blockNumber: [Getter],
            getBlockNumber: [Object],
            protocolVersion: [Getter],
            getProtocolVersion: [Object],
            iban: [Object],
            sendIBANTransaction: [Function: bound transfer] },
         transactionHash: null,
         address: '0x471a22ffe2bddd02e82853059871067e4c07a7f4',
         abi: [ [Object] ],
         sayHello: 
          { [Function: bound ]
            request: [Function: bound ],
            call: [Function: bound ],
            sendTransaction: [Function: bound ],
            estimateGas: [Function: bound ],
            getData: [Function: bound ],
            '': [Circular] },
         allEvents: [Function: bound ] },
      sayHello: 
       { [Function]
         call: [Function],
         sendTransaction: [Function],
         request: [Function: bound ],
         estimateGas: [Function] },
      sendTransaction: [Function],
      send: [Function],
      allEvents: [Function: bound ],
      address: '0x471a22ffe2bddd02e82853059871067e4c07a7f4',
      transactionHash: null }
    truffle(development)> contract.sayHello.call()
    'Hello World'
    truffle(development)>

讲解

HelloWorld.deployed().then(instance => contract = instance)

`truffle console`中预载了`truffle-contract`函数库，以方便操作部署到区块链上的合约。

这边使用`HelloWorld.deployed().then`语句来取得`HelloWorld`合约的`Instance`（实例），并存到`contract`变量中，以方便后续的调用。

上面用的是`Javascript ES6+`的语法，这句也可以写成：

HelloWorld.deployed().then(instance => {
        contract = instance
    });

还可以用ES5的写法：

HelloWorld.deployed().then(function(instance) {
      hello = instance;
    });

truffle(development)> contract.sayHello.call()
    'Hello World'

这里直接呼叫`contract.sayHello()`也会得到一样的结果。`truffle-contract`提供使用`call()`来读取只读（read only）的数据，这样就不需提供`gas`。因此如果遇到的操作需要向区块链写入数据，我们就不能用`call`语句了。

如此一来，我们已写好并部署完成了第一个智能合约，也验证了合约确实可以运作。

## 加入新方法 ##

我们在`HelloWorld.sol`中再加入一个`echo`方法，`echo`方法接受输入一个参数，并回传传送的参数。

function echo(string name) constant returns (string) {
        return name;
    }

新的`echo`方法中传入了一个`name`参数。我们也为`echo`方法加入一个`constant`声明，表示调用这个方法并不会改变区块链的状态。如此一来，透过`truffle-contract`来调用此方法时，会自动选用`call`来呼叫，也不需要额外提供gas。

由于更新了合约内容，我们需要先重新新编译一次，将编译结果部署到`testrpc`上，再透过`truffle console`执行看看结果。

liyuechun:HelloWorld yuechunli$ ls
    build		contracts	migrations	test		truffle.js
    liyuechun:HelloWorld yuechunli$ truffle compile
    Compiling ./contracts/HelloWorld.sol...
    Writing artifacts to ./build/contracts
    
    liyuechun:HelloWorld yuechunli$ truffle migrate --reset
    Using network 'development'.
    
    Running migration: 1_initial_migration.js
      Replacing Migrations...
      ... 0x64cdc42e08a7e3f8070c46d4877ba246d95cbbccbfe1b9abd2450cfc02b48eda
      Migrations: 0x42843f6a470b84e2669f19686a223c1bdefb6f4d
    Saving successful migration to network...
      ... 0x57042b767c0f40a4f88ce855e39549010d6d5ae5f880771a45c1f7f36ea0e5b3
    Saving artifacts...
    Running migration: 2_deploy_contracts.js
      Replacing HelloWorld...
      ... 0x2330e3264aae9d6be3744d8fc71d235fc6dc2934d33ff5159ae209df4cf8f12b
      HelloWorld: 0xbf68789cdd6be1577339e8c739abfa1190c31b6c
    Saving successful migration to network...
      ... 0xb4b706d7004654215067ea5954a32f0562b32724d1c646dc43b688b466b10159
    Saving artifacts...
    liyuechun:HelloWorld yuechunli$ truffle console
    truffle(development)> let contract
    undefined
    truffle(development)> HelloWorld.deployed().then(instance => contract = instance)
    TruffleContract {
      constructor: 
       { [Function: TruffleContract]
         _static_methods: 
          { setProvider: [Function: setProvider],
            new: [Function: new],
            at: [Function: at],
            deployed: [Function: deployed],
            defaults: [Function: defaults],
            hasNetwork: [Function: hasNetwork],
            isDeployed: [Function: isDeployed],
            detectNetwork: [Function: detectNetwork],
            setNetwork: [Function: setNetwork],
            resetAddress: [Function: resetAddress],
            link: [Function: link],
            clone: [Function: clone],
            addProp: [Function: addProp],
            toJSON: [Function: toJSON] },
         _properties: 
          { contract_name: [Object],
            abi: [Object],
            network: [Function: network],
            networks: [Function: networks],
            address: [Object],
            links: [Function: links],
            events: [Function: events],
            binary: [Function: binary],
            unlinked_binary: [Object],
            schema_version: [Function: schema_version],
            updated_at: [Function: updated_at] },
         _property_values: {},
         _json: 
          { contract_name: 'HelloWorld',
            default_network: undefined,
            abi: [Array],
            unlinked_binary: '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',
            networks: [Object],
            schema_version: '0.0.5',
            updated_at: 1505809278810 },
         setProvider: [Function: bound setProvider],
         new: [Function: bound new],
         at: [Function: bound at],
         deployed: [Function: bound deployed],
         defaults: [Function: bound defaults],
         hasNetwork: [Function: bound hasNetwork],
         isDeployed: [Function: bound isDeployed],
         detectNetwork: [Function: bound detectNetwork],
         setNetwork: [Function: bound setNetwork],
         resetAddress: [Function: bound resetAddress],
         link: [Function: bound link],
         clone: [Function: bound clone],
         addProp: [Function: bound addProp],
         toJSON: [Function: bound toJSON],
         web3: 
          Web3 {
            _requestManager: [Object],
            currentProvider: [Object],
            eth: [Object],
            db: [Object],
            shh: [Object],
            net: [Object],
            personal: [Object],
            bzz: [Object],
            settings: [Object],
            version: [Object],
            providers: [Object],
            _extend: [Object] },
         class_defaults: 
          { from: '0xbbd414b340f2255dab9d923428c97f0b65d9df81',
            gas: 4712388,
            gasPrice: 100000000000 },
         currentProvider: 
          HttpProvider {
            host: 'http://localhost:8545',
            timeout: 0,
            send: [Function],
            sendAsync: [Function],
            _alreadyWrapped: true },
         network_id: '1505794143155' },
      abi: 
       [ { constant: false,
           inputs: [],
           name: 'sayHello',
           outputs: [Array],
           payable: false,
           type: 'function' },
         { constant: true,
           inputs: [Array],
           name: 'echo',
           outputs: [Array],
           payable: false,
           type: 'function' } ],
      contract: 
       Contract {
         _eth: 
          Eth {
            _requestManager: [Object],
            getBalance: [Object],
            getStorageAt: [Object],
            getCode: [Object],
            getBlock: [Object],
            getUncle: [Object],
            getCompilers: [Object],
            getBlockTransactionCount: [Object],
            getBlockUncleCount: [Object],
            getTransaction: [Object],
            getTransactionFromBlock: [Object],
            getTransactionReceipt: [Object],
            getTransactionCount: [Object],
            call: [Object],
            estimateGas: [Object],
            sendRawTransaction: [Object],
            signTransaction: [Object],
            sendTransaction: [Object],
            sign: [Object],
            compile: [Object],
            submitWork: [Object],
            getWork: [Object],
            coinbase: [Getter],
            getCoinbase: [Object],
            mining: [Getter],
            getMining: [Object],
            hashrate: [Getter],
            getHashrate: [Object],
            syncing: [Getter],
            getSyncing: [Object],
            gasPrice: [Getter],
            getGasPrice: [Object],
            accounts: [Getter],
            getAccounts: [Object],
            blockNumber: [Getter],
            getBlockNumber: [Object],
            protocolVersion: [Getter],
            getProtocolVersion: [Object],
            iban: [Object],
            sendIBANTransaction: [Function: bound transfer] },
         transactionHash: null,
         address: '0xbf68789cdd6be1577339e8c739abfa1190c31b6c',
         abi: [ [Object], [Object] ],
         sayHello: 
          { [Function: bound ]
            request: [Function: bound ],
            call: [Function: bound ],
            sendTransaction: [Function: bound ],
            estimateGas: [Function: bound ],
            getData: [Function: bound ],
            '': [Circular] },
         echo: 
          { [Function: bound ]
            request: [Function: bound ],
            call: [Function: bound ],
            sendTransaction: [Function: bound ],
            estimateGas: [Function: bound ],
            getData: [Function: bound ],
            string: [Circular] },
         allEvents: [Function: bound ] },
      sayHello: 
       { [Function]
         call: [Function],
         sendTransaction: [Function],
         request: [Function: bound ],
         estimateGas: [Function] },
      echo: 
       { [Function]
         call: [Function],
         sendTransaction: [Function],
         request: [Function: bound ],
         estimateGas: [Function] },
      sendTransaction: [Function],
      send: [Function],
      allEvents: [Function: bound ],
      address: '0xbf68789cdd6be1577339e8c739abfa1190c31b6c',
      transactionHash: null }
    truffle(development)> contract.echo("春哥微信:liyc1215")
    '春哥微信:liyc1215'
    truffle(development)>

`echo`方法确实将我们输入的内容回传了。同时因为声明了constant，我们不需要直接调用`call()`方法，`truffle`会自动选用`call`来呼叫。

另一点需要注意的，是这次如果还是用`truffle migrate`命令，我们会得到如下信息：

$ truffle migrate
    Using network 'development'.
    Network up to date.

`Truffle`会告诉你现在网络上的合约都已是最新的，但事实上刚刚程序中新增的方法并没有更新到内存块链上。要更新内存块链上已部署的程序，需要改写`migrations`中的脚本，但现在还不到介绍`migration`的时候。还好我们开发用的内存块链是怎么修改都没关系的`testrpc`，可以使用`truffle migrate --reset`命令直接重新在`testrpc`上部署一次。

## 总结 ##

这篇文章非常简单，通过这篇文章，你将掌握如何配置开发环境、如何创建新项目、如何编译、如何部署合约以及了解整个智能合约开发的流程。

## 参考资料 ##

*  \[1\] [http://solidity.readthedocs.io/en/latest/index.html][http_solidity.readthedocs.io_en_latest_index.html]
 *  \[2\] [https://ethereum.github.io/browser-solidity/][https_ethereum.github.io_browser-solidity]
 *  \[3\] [http://truffleframework.com/][http_truffleframework.com]
 *  \[4\] [https://github.com/iurimatias/embark-framework][https_github.com_iurimatias_embark-framework]
 *  \[5\] [https://github.com/ethereum/ens][https_github.com_ethereum_ens]
 *  \[6\] [https://github.com/ethereumjs/testrpc][https_github.com_ethereumjs_testrpc]
 *  \[7\] [https://github.com/ethereumjs/ethereumjs-vm][https_github.com_ethereumjs_ethereumjs-vm]
 *  \[8\] [http://web3js.readthedocs.io/en/1.0/index.html][http_web3js.readthedocs.io_en_1.0_index.html]

[http_liyuechun.org_2017_09_19_how-to-code-smart-contract]: http://liyuechun.org/2017/09/19/how-to-code-smart-contract/
[https_truffleframework.com_docs_advanced_configuration_resolving-naming-conflicts-on-windows]: https://truffleframework.com/docs/advanced/configuration#resolving-naming-conflicts-on-windows
[Snip20170919_6.png]: http://om1c35wrq.bkt.clouddn.com/Snip20170919_6.png
[Snip20170919_7.png]: http://om1c35wrq.bkt.clouddn.com/Snip20170919_7.png
[Snip20170919_8.png]: http://om1c35wrq.bkt.clouddn.com/Snip20170919_8.png
[Snip20170919_12.png]: http://om1c35wrq.bkt.clouddn.com/Snip20170919_12.png
[Snip20170919_13.png]: http://om1c35wrq.bkt.clouddn.com/Snip20170919_13.png
[Snip20170919_14.png]: http://om1c35wrq.bkt.clouddn.com/Snip20170919_14.png
[Snip20170919_15.png]: http://om1c35wrq.bkt.clouddn.com/Snip20170919_15.png
[Snip20170919_17.png]: http://om1c35wrq.bkt.clouddn.com/Snip20170919_17.png
[Snip20170919_18.png]: http://om1c35wrq.bkt.clouddn.com/Snip20170919_18.png
[http_solidity.readthedocs.io_en_latest_index.html]: http://solidity.readthedocs.io/en/latest/index.html
[https_ethereum.github.io_browser-solidity]: https://ethereum.github.io/browser-solidity/
[http_truffleframework.com]: http://truffleframework.com/
[https_github.com_iurimatias_embark-framework]: https://github.com/iurimatias/embark-framework
[https_github.com_ethereum_ens]: https://github.com/ethereum/ens
[https_github.com_ethereumjs_testrpc]: https://github.com/ethereumjs/testrpc
[https_github.com_ethereumjs_ethereumjs-vm]: https://github.com/ethereumjs/ethereumjs-vm
[http_web3js.readthedocs.io_en_1.0_index.html]: http://web3js.readthedocs.io/en/1.0/index.html