Truffle合约交互 - WEB端对以太坊数据的读写
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Truffle合约交互 - WEB端对以太坊数据的读写
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1. 初始化truffle
truffle init webpack- 1
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可以參考：here
2. 寫一個(gè)合約
這里給出一個(gè)簡(jiǎn)單的合約。
pragma solidity ^0.4.2;contract Credit {event createRecord(address indexed _address, string identity, uint category, uint price);string a;uint b;uint c;function create(string identity, uint category, uint256 price){a = identity;b = category;c = price;createRecord(msg.sender, identity, category, price);}function all() returns (string, uint, uint){return(a, b, c);}}- 1
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3. 部署合約
前文有提到：here
4. 修改HTML文件
這里假設(shè)已經(jīng)有了web基礎(chǔ)。
寫3個(gè)input, 分別是身份、分類以及價(jià)格。注意它們的id
以及2個(gè)按鈕：
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5. 修改app.js文件
注意引入的文件。
// Import the page's CSS. Webpack will know what to do with it. import "../stylesheets/app.css";// Import libraries we need. import { default as Web3} from 'web3'; import { default as contract } from 'truffle-contract'// Import our contract artifacts and turn them into usable abstractions. import credit_artifacts from '../../build/contracts/Credit.json'// MetaCoin is our usable abstraction, which we'll use through the code below. var Credit = contract(credit_artifacts);//展示與合約的互動(dòng) var accounts; var account;window.App = {start: function() {var self = this;// Bootstrap the Credit abstraction for Use.Credit.setProvider(web3.currentProvider);//獲取初始賬戶web3.eth.getAccounts(function(err, accs) {if (err != null) {alert("There was an error fetching your accounts.");return;}if (accs.length == 0) {alert("Couldn't get any accounts! Make sure your Ethereum client is configured correctly.");return;}accounts = accs;account = accounts[0];// self.refreshBalance();});},//設(shè)置頁面文字信息setStatus: function(message) {var status = document.getElementById("status");status.innerHTML = message;},//從以太坊獲取信息getMessage: function(){var self = this;var meta;var a,b,c;Credit.deployed().then(function(instance) {meta = instance;return meta.all.call({from: account});}).then(function(value){self.setStatus(value);}).catch(function(e) {console.log(e);self.setStatus("Error getting message. see log.");});},//寫數(shù)據(jù)到以太坊saveMessage: function(){var self = this;var meta;var identity = document.getElementById("identity").value;var category = parseInt(document.getElementById("category").value);var price = parseInt(document.getElementById("price").value);Credit.deployed().then(function(instance) {meta = instance;return meta.create(identity, category, price, {from: account});}).then(function(){self.setStatus(identity);}).catch(function(e){console.log(e);self.setStatus("Error");});} };//下面這一段應(yīng)該是不用管照抄就行了。web頁面加載會(huì)調(diào)用。但實(shí)際上我還沒理解，待解決。 window.addEventListener('load', function() {if (typeof web3 !== 'undefined') {console.warn("Using web3 detected from external source. If you find that your accounts don't appear or you have 0 MetaCoin, ensure you've configured that source properly. If using MetaMask, see the following link. Feel free to delete this warning. :) http://truffleframework.com/tutorials/truffle-and-metamask")// Use Mist/MetaMask's providerwindow.web3 = new Web3(web3.currentProvider);} else {console.warn("No web3 detected. Falling back to http://localhost:8545. You should remove this fallback when you deploy live, as it's inherently insecure. Consider switching to Metamask for development. More info here: http://truffleframework.com/tutorials/truffle-and-metamask");// fallback - use your fallback strategy (local node / hosted node + in-dapp id mgmt / fail)window.web3 = new Web3(new Web3.providers.HttpProvider("http://localhost:8545"));}App.start(); });- 1
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參考：here
記錄一下自己遇到的問題：
剛開始寫法：
event createRecord(string identity, uint category, uint price); 調(diào)用時(shí)：createRecord(identity, category, price);- 1
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得到的identity不是輸入的字符串而是一串類似于下面這樣的數(shù)據(jù)
0x4f6054c80000000000000000000000000000000000000000- 1
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解決：
event createRecord(address indexed _address, string identity, uint category, uint price);調(diào)用時(shí)：createRecord(msg.sender, identity, category, price);- 1
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可以看到加了一個(gè)地址，這個(gè)事件是用來廣播的，第一個(gè)參數(shù)是用來部署合約的地址。
版權(quán)聲明：本文為博主原創(chuàng)文章，未經(jīng)博主允許不得轉(zhuǎn)載。 http://blog.csdn.net/loy_184548/article/details/78041350總結(jié)
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