科普 | 智能合约event调用实例-墨客（MOAC）中文社区

墨染芳华

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墨客战士

event调用过程：首先需要在合约中定义event，并在某个函数中去触发它。当我们调用该函数的时候就会触发event，然后，可以通过在该次调用智能合约产生的block上建立filter来捕获event。

环境：

墨客区块链版本：nuwa1.0.5.win.zip；

操作系统：64位Windows 10家庭版。

部署标准ERC20合约

1. 启动本地节点

D:\nuwa1.0.5.win\win\vnode>moac --rpc --rpcaddr 0.0.0.0 --rpccorsdomain "*" --rpcapi="db,mc,net,chain3,personal,vnode,debug,scs"

2. 按照《第四篇墨客区块链(MOAC BlockChain) 部署ERC-20合约》部署智能合约。

监测智能合约事件

代码如下：

#!/usr/bin/env node

Test the ERC20 contract interface on MOAC network.

This test requires a running MOAC node with RPC http port open at 8545

and the contract address and abi.

1. Connect to a local MOAC node.

2. Load the contract address and abi.

3. Setup a filter of the contract and watch the event, such as transfer.

var Chain3 = require('chain3');

var chain3 = new Chain3(new Chain3.providers.HttpProvider('http://localhost:8545'));

var tokenabi='[ { "constant": true, "inputs": [], "name": "name", ............, { "indexed": false, "name": "_value", "type": "uint256" } ], "name": "Approval", "type": "event" } ]';

//Load the contract ABI

var tokenContract=chain3.mc.contract(JSON.parse(tokenabi));

var myContractInstance = tokenContract.at('0xA2580D58A58998ca06e6f5b2A96A95D8d48f1679'); //智能合约地址

chain3.setProvider(new chain3.providers.HttpProvider('http://localhost:8545'));

if ( chain3.isConnected() ){

console.log("RPC connected, check token balance");

// watch for an event with {some: 'args'}

var events = myContractInstance.allEvents({fromBlock: 0, toBlock: 'latest'});

events.watch(function(error, result){

if( !error )

{

var msg = result.blockNumber;

console.log( msg + ":" + JSON.stringify(result.TxData))

}

else{

console.log("err:" + error);

}

});

}else{

console.log("RPC not connected!");

}

return;

运行后处于侦听状态

操作合约的transfer，查看监测

在 http://wallet.moac.io/ 对erc20合约进行一次transfer操作。

打包后，检测程序显示与浏览器内容一致：

附录：对合约的调用操作

#!/usr/bin/env node

Test the ERC20 contract interface on MOAC network.

This test requires a running MOAC node with RPC http port open at 8545

and the contract address and abi.

1. Connect to a local MOAC node.

2. Load the contract address and abi.

var Chain3 = require('chain3');

var chain3 = new Chain3(new Chain3.providers.HttpProvider('http://localhost:8545'));

//Set the contract ABI and address to use

//The ABI info can be obtained using REMIX

//The address is the contract HASH after deploying the contract.

var tokenabi='[ { "constant": true, "inputs": [], "name": "name",............, "name": "Approval", "type": "event" } ]';

//Load the contract ABI

var tokenContract=chain3.mc.contract(JSON.parse(tokenabi));

//Testnetwork token, networkid = 101

var tokenaddress='0xA2580D58A58998ca06e6f5b2A96A95XXXXXXXXXX';

//Load the contract methods

var tcalls=tokenContract.at(tokenaddress);

//check the balance

var totalBal = 0;

//test accounts

//Need to add the addr and private key for your own ERC20 tokens

var taccts = [{

"addr": "0x68986c1BCD54Ae5dAe69310fC64Ea5XXXXXXXXXX",

"key": "9a863cb325ba30b5f41bd285e80c14c2d96f86b21e90XXXXXXXXXXXXXXXXXXXX"

},{

"addr": "0x745c57ca5318093115D61Bbca3687cXXXXXXXXXX",

"key": ""

}];

//Connect the local MOAC node through HTTP

chain3.setProvider(new chain3.providers.HttpProvider('http://localhost:8545'));

if ( chain3.isConnected() ){

console.log("RPC connected, check token balance");

// console.log("code len:", chain3.mc.getCode(tokenaddress));

var contractCode = chain3.mc.getCode(tokenaddress);

if (contractCode == '0x') {

console.log("Contract address has no data!");

return;

}

//Get token Info

console.log("Token Info\nfull name:", tcalls.name());

console.log(" symbol:", tcalls.symbol());

var src = taccts[0].addr;

var des = "0x745c57ca5318093115D61Bbca3687cXXXXXXXXXX";//taccts[1].addr;

console.log("src bal:", src, ":",tcalls.balanceOf(src).toString(10));

console.log("des bal:", des, ":",tcalls.balanceOf(des).toString(10));

//var strData = '';

var srcVal = tcalls.balanceOf(src);

var desVal = tcalls.balanceOf(des);

var amt = 123;//amout in erc20 token "m02"

console.log(" Transfer from:\n", src, "\n to \n", des);

var tcalldata = tcalls.transfer.getData(des, amt);

console.log("\n Tcalldata:", tcalldata);

let gasEstimate = chain3.mc.estimateGas({data: tcalldata});

gasEstimate = 4000000;

//The sign of the transaction requires the correct network id

var networkid = chain3.version.network;

console.log("On network:", networkid);

//Add some more gas on the estimate to ensure the call can be processed

callContractMethod(taccts[0], tokenaddress, gasEstimate+100, networkid, tcalldata);

}else

console.log("RPC not connected!");

* Call a contract with the input byteCode

function callContractMethod(src, contractAddress, gasValue, inchainID, inByteCode){

var txcount = chain3.mc.getTransactionCount(src["addr"]);

console.log("Get tx account", txcount)

//Build the raw tx obj

//note the transaction

var rawTx = {

from: src.addr,

to: contractAddress,

nonce: chain3.intToHex(txcount),

gasPrice: chain3.intToHex(30000000000),

gasLimit: chain3.intToHex(gasValue),

value: '0x',

data: inByteCode,

chainId: chain3.intToHex(inchainID)

}

console.log(rawTx);

var cmd1 = chain3.signTransaction(rawTx, src["key"]);

console.log("\nSend signed TX:\n", cmd1);

chain3.mc.sendRawTransaction(cmd1, function(err, hash) {

if (!err){

console.log("Succeed!: ", hash);

return hash;

}else{

console.log("Chain3 error:", err.message);

return err.message;

}

console.log("Get response from MOAC node in the feedback function!")

// res.send(response);

});

}

追踪我们：

官网：www.moacfoundation.org

Twitter：https://twitter.com/moac_io

FB: https://www.facebook.com/moacchain/

Medium: https://medium.com/moac

Telegram: https://t.me/moacblockchain

Telegram: https://t.me/MOACDevelopers

Reddit: https://www.reddit.com/r/MOAC/

Github: https://github.com/MOACChain

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