以太坊学习笔记（七）——Truffle集成Nodejs

这篇文章的内容紧接着上章的内容，上一篇讲了truffle合约部署的基本操作，文章最后讲了通过console来调用部署成功的合约中的方法，之所以truffle console能够直接调用合约中的方式，是因为truffle console默认集成了web3。如果想在NodeJS环境使用Truffle合约，就要手动集成这两个模块。
集成NodeJS
1.首先需要安装npm包管理器，这里就不讲安装过程，如果已经安装过最好把npm更新到最新版本，不然在后面的操作中可能会报错，以下就是我在操作过程中遇到的一个错误。

 var BigNumber = (new Web3()).toBigNumber(0).constructor;
                               ^
TypeError: (intermediate value).toBigNumber is not a function

2.创建工程的npm包管理器，这里我们还是以上一个项目为例，进入项目所在的目录，使用npm init来初始化工程的npm包管理环境。

$ npm init
This utility will walk you through creating a package.json file.
It only covers the most common items, and tries to guess sensible defaults.

See `npm help json` for definitive documentation on these fields
and exactly what they do.

Use `npm install ` afterwards to install a package and
save it as a dependency in the package.json file.

Press ^C at any time to quit.
package name: (truffletest) truffletest //回车或输入括号内的包名
version: (1.0.0) 1.0.0 //同上
license: (ISC) //同上
About to write to /Users/cyril/Desktop/truffleTest/package.json:

{
  "name": "truffletest",
  "version": "1.0.0",
  "description": "truffle with nodejs",
  "main": "main.js",
  "directories": {
    "test": "test"
  },
  "scripts": {
    "test": "truffletest"
  },
  "repository": {
    "type": "git",
    "url": "main.js"
  },
  "keywords": [
    "truffletest"
  ],
  "author": "cyril",
  "license": "ISC",
  "dependencies": {
    "truffle-contract": "^3.0.6",
    "web3": "^1.0.0-beta2"
  }
}

Is this OK? (yes) yes //同前面的操作

这个时候项目会生成package.json和package-lock.json同时会添加node-modules相关的库依赖，生成的这些文件没必要去修改
项目结构如下：

安装NodeJS中用到的Truffle合约抽象层运行环境
truffle-contract是Truffle提供的，用于在NodeJS和浏览器中集成Truffle的合约抽象运行环境。

$ npm install truffle-contract

npm notice created a lockfile as package-lock.json. You should commit this file.
+ truffle-contract@3.0.6
added 24 packages from 18 contributors and audited 25 packages in 13.15s
found 0 vulnerabilities

安装NodeJS中用到的Truffle运行时需要的web3环境

$ npm install web3

npm WARN deprecated web3@1.0.0-beta2: This version has faulty dependecy links.
+ web3@1.0.0-beta2
added 1 package from 1 contributor and audited 26 packages in 1.752s
found 0 vulnerabilities

测试合约
这里就用前面的Test.sol和Greeter.sol，部署流程就不讲了，在项目根目录下创建main.js，内容大体结构如下

//引入依赖，并初始化一个实例Web3
var Web3 = require('web3');
var provider = new Web3.providers.HttpProvider("http://localhost:8545");

//省略了无关代码
//合约初始化
var Test = contract(/*合约JSON*/);//合约的元数据 

//设置连接
Test.setProvider(provider);

//设置默认地址
Test.defaults({
  from : "0x299127d72e28cb92d09f856aaedeb139d1e7e74a"
});

//函数调用
//TODO

我们拿Test举个例子：

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

var provider = new Web3.providers.HttpProvider("http://localhost:8545");


//使用truffle-contract包的contract()方法
//请务必使用你自己编译的.json文件内容
var Test = contract({
    "contractName": "Test",
    "abi": [
        {
            "constant": true,
            "inputs": [],
            "name": "f",
            "outputs": [
                {
                    "name": "",
                    "type": "string"
                }
            ],
            "payable": false,
            "stateMutability": "pure",
            "type": "function"
        },
        {
            "constant": true,
            "inputs": [],
            "name": "g",
            "outputs": [
                {
                    "name": "",
                    "type": "string"
                }
            ],
            "payable": false,
            "stateMutability": "pure",
            "type": "function"
        }
    ],
    "networks": {
        "1536568575803": {
            "events": {},
            "links": {},
            "address": "0x57fec0a6d60ce7a133bbc6f7ac64f99a7b97425f",
            "transactionHash": "0x84463c7b8bce644a4df200ed1afdb3714514696cb32eef443854ca2dc2e56a70"
        },
        "1536655141628": {
            "events": {},
            "links": {},
            "address": "0x03873f72987988a143d514f43a6c548fe8d252b9",
            "transactionHash": "0xd3b7577fb5aae6a5950c0b2e04e1211f26ce487dda065d264bf6c61e2b453983"
        }
    },
    "schemaVersion": "2.0.1",
    "updatedAt": "2018-09-11T09:04:16.743Z"
});
Test.setProvider(provider);
//随便从testrpc提供的地址中拷贝一个
Test.defaults({
    from: "0x807b0d9ffc27ecdc481bd1fc84fd3d4fb054c324" 
});

//调用合约方法
var instance;
Test.deployed().then(function (func) {
    instance = func;
    return instance.f.call();
}).then(function (value) {
    console.log(value);
    return instance.g.call();
}).then(function (value) {
    console.log(value);
});

注意：
1.最好原封不动的把json文件的内容拷贝过来，为了节约篇幅，我就只粘贴了部分，虽然不影响正常测试，但可能遇到下面的错误：

node_modules/truffle->contract/node_modules/web3/lib/web3/contract.js:56
 contract.abi.filter(function (json) {
               ^
TypeError: Cannot read property 'filter' of undefined

2.必须设置默认账户，truffle-contract框架默认没有读取coinbase的默认地址，所以需要主动设置，不然会报如下错误：

(node:26922) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): Error: invalid address

运行main.js
运行main.js，然后报了如下错：

$ node main.js 

module.js:487
    throw err;
    ^
Error: Cannot find module 'web3-requestManager'

这个问题就是我开篇说的一定要注意运行环境的版本，这个问题是因为package.json中依赖的web3版本是^1.0.0-beta2，这个问题可以通过安装依赖解决

$ npm install ethereum/web3.js

+ web3@0.20.7
added 4 packages from 4 contributors, updated 1 package and audited 32 packages in 58.834s
found 0 vulnerabilities

再次查看package.json中的web3版本已经变成了github:ethereum/web3.js，然后再次运行main.js

$ node main.js 

method f()
method g()

输出结果跟上篇内容的一样，也在预料之中。不论是合约中的f()方法还是g()方法，都不会改写区块链状态，使用instance.f.call()调用；而对于一个会改写区块链状态的函数f()，使用instance.f()调用，我们在以Greeter.sol为例来演示一下
下面的代码依然是放在main.js里

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

var provider = new Web3.providers.HttpProvider("http://localhost:8545");

var Greeter = contract({
    "contractName": "Greeter",
    "abi": [
        {
            "inputs": [],
            "payable": false,
            "stateMutability": "nonpayable",
            "type": "constructor"
        },
        {
            "constant": true,
            "inputs": [],
            "name": "greet",
            "outputs": [
                {
                    "name": "",
                    "type": "string"
                }
            ],
            "payable": false,
            "stateMutability": "view",
            "type": "function"
        },
        {
            "constant": false,
            "inputs": [
                {
                    "name": "_newgreeting",
                    "type": "string"
                }
            ],
            "name": "setGreeting",
            "outputs": [],
            "payable": false,
            "stateMutability": "nonpayable",
            "type": "function"
        },
        {
            "constant": false,
            "inputs": [],
            "name": "kill",
            "outputs": [],
            "payable": false,
            "stateMutability": "nonpayable",
            "type": "function"
        }
    ],
    "networks": {
        "1536568575803": {
            "events": {},
            "links": {},
            "address": "0x4cf91392df7740176d74f63faf9991ec838a6473",
            "transactionHash": "0x33b9776384f25342d51799970744b44dcfedf55a36093d55a72c5323dcbc8cf5"
        },
        "1536655141628": {
            "events": {},
            "links": {},
            "address": "0x2eb0113712145ffb42889c9421a6881e864ff2b4",
            "transactionHash": "0x748948df55b1597223d54cc6184d7a43ac47a04a559fafd9eb49e3c02c1abe98"
        }
    },
    "schemaVersion": "2.0.1",
    "updatedAt": "2018-09-11T09:04:16.744Z"
});

Greeter.setProvider(provider);
Greeter.defaults({
    from: "0xd10e318f0ef3e74c6e75e0827b840b2d00a49af5"
});

var ins;
Greeter.deployed().then(function (value) {
    ins = value;
    return ins.setGreeting("hello");
}).then(function (value) {
    console.log(value);
    return ins.greet.call();
}).then(function (value) {
    console.log(value);
});

运行

$ node main.js 
{ tx: '0x887d1043feb6f1e65bd90c71840b6b8fe8b2eea6ac19ad82dbd3c61c8eccae4c',
  receipt: 
   { transactionHash: '0x887d1043feb6f1e65bd90c71840b6b8fe8b2eea6ac19ad82dbd3c61c8eccae4c',
     transactionIndex: 0,
     blockHash: '0x323b5d22dbea9f4d7c1e70da5a0dc2b4b96f453afd6a3ae80c989470804c6562',
     blockNumber: 17,
     gasUsed: 33090,
     cumulativeGasUsed: 33090,
     contractAddress: null,
     logs: [],
     status: 1 },
  logs: [] }
//greet()方法输出内容
hello

因为ins.setGreeting ()方法会改变区块链状态，所以需要消耗gas，同时在调用的时候返回对应的交易状态结果。