本文章的项目基于春哥的博客教程
【IPFS + 区块链 系列】 入门篇 - IPFS + Ethereum （下篇）-ipfs + Ethereum 大图片存储
我个人只是作为记录学习心得所借鉴
项目流程
首先调用代码创建truffle项目
truffle unbox react
其次，要引入ipfs的api，用作图片存储的相关功能，我们是将图片存储到ipfs当中，而将所获得图片的hash区块链之中，区块链大数据成本的问题
npm install –save ipfs-api
安装完毕调用complie编译合约代码,，以便使用web3调用合约存储区块链
compile
替换合约地址，这个需要将合约在以太坊部署并取得对应地址
然后运行ipfs节点
ipfs daemon
启动项目
npm start
就可以看到项目成功
代码解读分析
import React, {Component} from 'react'
import SimpleStorageContract from '../build/contracts/SimpleStorage.json'
import getWeb3 from './utils/getWeb3'
import './css/oswald.css'
import './css/open-sans.css'
import './css/pure-min.css'
import './App.css'
const ipfsAPI = require('ipfs-api');
const ipfs = ipfsAPI({host: 'localhost', port: '5001', protocol: 'http'});
const contract = require('truffle-contract')
const simpleStorage = contract(SimpleStorageContract)
let account;
/** Declaring this for later so we can chain functions on SimpleStorage.**/
let contractInstance;
//ipfs保存图片方法//
let saveImageOnIpfs = (reader) => {
return new Promise(function(resolve, reject) {
const buffer = Buffer.from(reader.result);
ipfs.add(buffer).then((response) => {
console.log(response)
resolve(response[0].hash);
}).catch((err) => {
console.error(err)
reject(err);
})
})
}
//创建构造函数，添加状态机变量//
class App extends Component {
constructor(props) {
super(props)
this.state = {
blockChainHash: null,
web3: null,
address: null,
imgHash: null,
isWriteSuccess: false
}
}
//程序启动默认调用方法//
componentWillMount() {
//打印项目中网络节点//
ipfs.swarm.peers(function(err, res) {
if (err) {
console.error(err);
} else {
/** var numPeers = res.Peers === null ? 0 : res.Peers.length;**/
/** console.log("IPFS - connected to " + numPeers + " peers");**/
console.log(res);
}
});
//web3设置，同时调用初始化方法//
getWeb3.then(results => {
this.setState({web3: results.web3})
// Instantiate contract once web3 provided.
this.instantiateContract()
}).catch(() => {
console.log('Error finding web3.')
})
}
//初始化合约实例、web3获取合约账号以及合约实例//
instantiateContract = () => {
simpleStorage.setProvider(this.state.web3.currentProvider);
this.state.web3.eth.getAccounts((error, accounts) => {
account = accounts[0];
simpleStorage.at('0xf6a7e96860f05f21ecb4eb588fe8a8a83981af03').then((contract) => {
console.log(contract.address);
contractInstance = contract;
this.setState({address: contractInstance.address});
return;
});
})
}
render() {
return (<div className="App">
{
this.state.address
? <h1>合约地址：{this.state.address}</h1>
: <div/>
}
<h2>上传图片到IPFS：</h2>
/**这一部分用于上传文件到ipfs**/
<div>
<label id="file">Choose file to upload</label>
<input type="file" ref="file" id="file" name="file" multiple="multiple"/>
</div>
<div>
<button onClick={() => {
var file = this.refs.file.files[0];
var reader = new FileReader();
// reader.readAsDataURL(file);
reader.readAsArrayBuffer(file)
reader.onloadend = function(e) {
console.log(reader);
saveImageOnIpfs(reader).then((hash) => {
console.log(hash);
this.setState({imgHash: hash})
});
}.bind(this);
}}>将图片上传到IPFS并返回图片HASH</button>
</div>
/**这一部分用于上传hash到区块链**/
{
this.state.imgHash
? <div>
<h2>imgHash：{this.state.imgHash}</h2>
<button onClick={() => {
contractInstance.set(this.state.imgHash, {from: account}).then(() => {
console.log('图片的hash已经写入到区块链！');
this.setState({isWriteSuccess: true});
})
}}>将图片hash写到区块链：contractInstance.set(imgHash)</button>
</div>
: <div/>
}
{
this.state.isWriteSuccess
? <div>
<h1>图片的hash已经写入到区块链！</h1>
<button onClick={() => {
contractInstance.get({from: account}).then((data) => {
console.log(data);
this.setState({blockChainHash: data});
})
}}>从区块链读取图片hash：contractInstance.get()</button>
</div>
: <div/>
}
{
this.state.blockChainHash
? <div>
<h3>从区块链读取到的hash值：{this.state.blockChainHash}</h3>
</div>
: <div/>
}
{
this.state.blockChainHash
? <div>
<h2>浏览器访问：{"http://localhost:8080/ipfs/" + this.state.imgHash}</h2>
<img alt="" style={{width:200}} src={"http://localhost:8080/ipfs/" + this.state.imgHash}/>
</div>
: <img alt=""/>
}
</div>);
}
}
export default App
该项目算是truffle和ipfs结合以太坊一起使用的综合案例，用与梳理知识点
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作者：czZ__czZ
来源：CSDN
原文：https://blog.csdn.net/czZ__czZ/article/details/79036567
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