【IPFS + 区块链 系列】 入门篇 - IPFS + Ethereum （下篇）-ipfs + Ethereum 大图片存储

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区块链视频网站：http://www.kongyixueyuan.com

Ebay项目

基于以太坊Ethereum & IPFS的去中心化Ebay区块链项目详情链接

目录

1. 系列文章

2. 项目描述及效果展示

这篇文章通过truffle unbox react创建项目，安装ipfs-api，将图片存储到ipfs，将图片hash存储到Ethereum区块链，取数据时先从区块链读取图片hash，再通过hash从ipfs读取数据，解决了区块链大数据存储成本高昂的问题。


3. 阅读本文需要掌握的知识

阅读本文需要将先学习上面的系列文章，由于本文前端使用了大量的React语法，所以建议学习一些React语法，还需要学习truffle framework。

4. 源码

其实这篇文章的内容就是上面几篇文章的综合结合体，所以在这里我将不再对代码做过多的概述。

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;

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); }) }) } class App extends Component { constructor(props) { super(props) this.state = { blockChainHash: null, web3: null, address: null, imgHash: null, isWriteSuccess: false } } componentWillMount() { 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); } }); getWeb3.then(results => { this.setState({web3: results.web3}) // Instantiate contract once web3 provided. this.instantiateContract() }).catch(() => { console.log('Error finding web3.') }) } instantiateContract = () => {

    simpleStorage.setProvider(this.state.web3.currentProvider);
    this.state.web3.eth.getAccounts((error, accounts) => { account = accounts[0]; simpleStorage.at('0x66e9bbfe244799149a9c4eb708a34ea7c9ce67e2').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> <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> { 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: 1600 }} src={"http://localhost:8080/ipfs/" + this.state.imgHash}/> </div> : <img alt=""/> } </div>); } } export default App

5. 运行程序

  • 项目下载
$ git clone https://github.com/liyuechun/IPFS-Ethereum-Image.git
$ cd IPFS-Ethereum-Image
$ npm install
  • 运行程序
$ ipfs daemon // 终端一
$ npm start   // 终端二

6. 技术交流

  • 区块链技术交流QQ群：348924182
  • 进微信群请加微信：liyc1215
  • 「区块链部落」官方公众号

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