2019獨角獸企業重金招聘Python工程師標準>>>

參考文檔。

例子代碼如下：

pragma solidity ^0.4.25;contract Assert{} contract TestReturn {Assert ast;event CreateAssertAll(Assert indexed _sig,uint256 indexed id);event CreateAssertOne(Assert indexed _sig,uint256 id);event Create(Assert _sig,uint256 id);function check() public returns(uint256) {ast = new Assert();emit CreateAssertAll(ast,uint256(6));emit CreateAssertOne(ast,uint256(6));emit Create(ast,uint256(6));}}

上面的代碼中，有3個event。他們的index不同。生成的log數據結構不一樣。

• CreateAssertAll全部是index。
• CreateAssertOne有一個是idnex。
• Create全部都不是index。
  我在ropsten上調用了這個方法。hash如下：
  https://ropsten.etherscan.io/tx/0x12e3384bdba97c631bbaa5df27e94e6baeb9ee894ee80c7d9ce0e1b9944b70d7
  可以查看生成的event：
  https://ropsten.etherscan.io/address/0x92e22427412dc8705b69c2db1b702d51586018f5#events

使用web3查看日志。

const Web3 = require('web3'); const web3 = new Web3(new Web3.providers.HttpProvider("https://ropsten.infura.io/XXX"));const SolidityCoder = require("web3/lib/solidity/coder.js"); web3.eth.getTransactionReceipt("0x12e3384bdba97c631bbaa5df27e94e6baeb9ee894ee80c7d9ce0e1b9944b70d7",function(error, result){if(!error){// console.log("receipt ==== ",result);let logs = result.logs;console.log("logs ==== ",logs);let data = SolidityCoder.decodeParams(["address", "uint256"], logs[2].data.replace("0x", ""));console.log("data ==== ",data);}elseconsole.error(error); });

可以看到打印日下：

logs ==== [ { address: '0x92e22427412dc8705b69c2db1b702d51586018f5',blockHash: '0x06cf0bd459caa91c9fd13a7b65875d300942648a975bf282813c4e1596258192',blockNumber: 4381899,data: '0x',logIndex: 3,removed: false,topics: [ '0xd39437daf43d90c2fc7f92c178818776f8ae6c1e6bde3215fa60b27756797d17','0x00000000000000000000000029f65c9a6f016ad76f5a26896343d3731267cc36','0x0000000000000000000000000000000000000000000000000000000000000006' ],transactionHash: '0x12e3384bdba97c631bbaa5df27e94e6baeb9ee894ee80c7d9ce0e1b9944b70d7',transactionIndex: 20 },{ address: '0x92e22427412dc8705b69c2db1b702d51586018f5',blockHash: '0x06cf0bd459caa91c9fd13a7b65875d300942648a975bf282813c4e1596258192',blockNumber: 4381899,data: '0x0000000000000000000000000000000000000000000000000000000000000006',logIndex: 4,removed: false,topics: [ '0xef0d7493287e1bf143771073deb917ba8ae1b8503a98a3d6d490d058e81d67ea','0x00000000000000000000000029f65c9a6f016ad76f5a26896343d3731267cc36' ],transactionHash: '0x12e3384bdba97c631bbaa5df27e94e6baeb9ee894ee80c7d9ce0e1b9944b70d7',transactionIndex: 20 },{ address: '0x92e22427412dc8705b69c2db1b702d51586018f5',blockHash: '0x06cf0bd459caa91c9fd13a7b65875d300942648a975bf282813c4e1596258192',blockNumber: 4381899,data: '0x00000000000000000000000029f65c9a6f016ad76f5a26896343d3731267cc360000000000000000000000000000000000000000000000000000000000000006',logIndex: 5,removed: false,topics: [ '0xcc9018de05b5f497ee7618d8830568d8ac2d45d0671b73d8f71c67e824122ec7' ],transactionHash: '0x12e3384bdba97c631bbaa5df27e94e6baeb9ee894ee80c7d9ce0e1b9944b70d7',transactionIndex: 20 } ] data ==== [ '0x29f65c9a6f016ad76f5a26896343d3731267cc36',BigNumber { s: 1, e: 0, c: [ 6 ] } ]

分析日志可以知道。

• 一共生成了3個日志。
• topics的第一個值topics[0]是sha3(event名字(參數1類型,參數2類型))
• 參數內容：如果event的參數是index，那就會在topics的值中。如果不是index，那就會在data中。

比較方便的解析方式：

let abi = ""; let SolidityEvent = require("web3/lib/web3/event.js"); let logParser = (logs, abi) => {// pattern similar to lib/web3/contract.js: addEventsToContract()let decoders = abi.filter(function (json) {return json.type === 'event';}).map(function(json) {// note first and third params required only by enocde and execute;// so don't call those!return new SolidityEvent(null, json, null);});return logs.map(function (log) {return decoders.find(function(decoder) {return (decoder.signature() == log.topics[0].replace("0x",""));}).decode(log);}) }; web3.eth.getTransactionReceipt("0x12e3384bdba97c631bbaa5df27e94e6baeb9ee894ee80c7d9ce0e1b9944b70d7",function(error, result){if(!error){// console.log("receipt ==== ",result);let logs = result.logs;let events = logParser(logs,JSON.parse(abi));console.log("logParser === ",events)}elseconsole.error(error); });

轉載于:https://my.oschina.net/kunBlog/blog/2873039

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