本文章的項目基于春哥的博客教程
【IPFS + 區(qū)塊鏈 系列】 入門篇 - IPFS + Ethereum （下篇）-ipfs + Ethereum 大圖片存儲
我個人只是作為記錄學習心得所借鑒
項目流程
首先調用代碼創(chuàng)建truffle項目
truffle unbox react
其次，要引入ipfs的api，用作圖片存儲的相關功能，我們是將圖片存儲到ipfs當中，而將所獲得圖片的hash區(qū)塊鏈之中，區(qū)塊鏈大數(shù)據(jù)成本的問題
npm install –save ipfs-api
安裝完畢調用complie編譯合約代碼,，以便使用web3調用合約存儲區(qū)塊鏈
compile
替換合約地址，這個需要將合約在以太坊部署并取得對應地址
然后運行ipfs節(jié)點
ipfs daemon
啟動項目
npm start
就可以看到項目成功
代碼解讀分析
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保存圖片方法//
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);
})
})
}
//創(chuàng)建構造函數(shù)，添加狀態(tài)機變量//
class App extends Component {
constructor(props) {
super(props)
this.state = {
blockChainHash: null,
web3: null,
address: null,
imgHash: null,
isWriteSuccess: false
}
}
//程序啟動默認調用方法//
componentWillMount() {
//打印項目中網(wǎng)絡節(jié)點//
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設置，同時調用初始化方法//
getWeb3.then(results => {
this.setState({web3: results.web3})
// Instantiate contract once web3 provided.
this.instantiateContract()
}).catch(() => {
console.log('Error finding web3.')
})
}
//初始化合約實例、web3獲取合約賬號以及合約實例//
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>合約地址：{this.state.address}</h1>
: <div/>
}
<h2>上傳圖片到IPFS：</h2>
/**這一部分用于上傳文件到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);
}}>將圖片上傳到IPFS并返回圖片HASH</button>
</div>
/**這一部分用于上傳hash到區(qū)塊鏈**/
{
this.state.imgHash
? <div>
<h2>imgHash：{this.state.imgHash}</h2>
<button onClick={() => {
contractInstance.set(this.state.imgHash, {from: account}).then(() => {
console.log('圖片的hash已經(jīng)寫入到區(qū)塊鏈！');
this.setState({isWriteSuccess: true});
})
}}>將圖片hash寫到區(qū)塊鏈：contractInstance.set(imgHash)</button>
</div>
: <div/>
}
{
this.state.isWriteSuccess
? <div>
<h1>圖片的hash已經(jīng)寫入到區(qū)塊鏈！</h1>
<button onClick={() => {
contractInstance.get({from: account}).then((data) => {
console.log(data);
this.setState({blockChainHash: data});
})
}}>從區(qū)塊鏈讀取圖片hash：contractInstance.get()</button>
</div>
: <div/>
}
{
this.state.blockChainHash
? <div>
<h3>從區(qū)塊鏈讀取到的hash值：{this.state.blockChainHash}</h3>
</div>
: <div/>
}
{
this.state.blockChainHash
? <div>
<h2>瀏覽器訪問：{"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
該項目算是truffle和ipfs結合以太坊一起使用的綜合案例，用與梳理知識點
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作者：czZ__czZ
來源：CSDN
原文：https://blog.csdn.net/czZ__czZ/article/details/79036567
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