使用web3进行合约部署调用以及监听

矫情吗；* 2022-05-17 06:51 819阅读 0赞

token合约是官方提供的一个样例,这里给出我修改过的版本,方便演示.

contract MyToken {
        /* Public variables of the token */
        string public name;
        string public symbol;
        uint8 public decimals;
    
        /* This creates an array with all balances */
        mapping (address => uint256) public balanceOf;
        mapping (address => mapping (address => uint)) public allowance;
        mapping (address => mapping (address => uint)) public spentAllowance;
    
        /* This generates a public event on the blockchain that will notify clients */
        event Transfer(address indexed from, address indexed to, uint256 value);
        event ReceiveApproval(address _from, uint256 _value, address _token, bytes _extraData);
    
        /* Initializes contract with initial supply tokens to the creator of the contract */
        function MyToken(uint256 initialSupply, string tokenName, uint8 decimalUnits, string tokenSymbol) {
            balanceOf[msg.sender] = initialSupply;              // Give the creator all initial tokens
            name = tokenName;                                   // Set the name for display purposes
            symbol = tokenSymbol;                               // Set the symbol for display purposes
            decimals = decimalUnits;                            // Amount of decimals for display purposes
        }
    
        /* Send coins */
        function transfer(address _to, uint256 _value) {
            if (balanceOf[msg.sender] < _value) throw;           // Check if the sender has enough
            if (balanceOf[_to] + _value < balanceOf[_to]) throw; // Check for overflows
            balanceOf[msg.sender] -= _value;                     // Subtract from the sender
            balanceOf[_to] += _value;                            // Add the same to the recipient
            Transfer(msg.sender, _to, _value);                   // Notify anyone listening that this transfer took place
        }
    
        /* Allow another contract to spend some tokens in your behalf */
    
        function approveAndCall(address _spender, uint256 _value, bytes _extraData) returns (bool success) {
            allowance[msg.sender][_spender] = _value;
            ReceiveApproval(msg.sender, _value, this, _extraData);
        }
    
        /* A contract attempts to get the coins */
    
        function transferFrom(address _from, address _to, uint256 _value) returns (bool success) {
            if (balanceOf[_from] < _value) throw;                 // Check if the sender has enough
            if (balanceOf[_to] + _value < balanceOf[_to]) throw;  // Check for overflows
            if (spentAllowance[_from][msg.sender] + _value > allowance[_from][msg.sender]) throw;   // Check allowance
            balanceOf[_from] -= _value;                          // Subtract from the sender
            balanceOf[_to] += _value;                            // Add the same to the recipient
            spentAllowance[_from][msg.sender] += _value;
            Transfer(msg.sender, _to, _value);
        }
    
        /* This unnamed function is called whenever someone tries to send ether to it */
        function () {
            throw;     // Prevents accidental sending of ether
        }
    }

## 编译token ##

通过solc编译得到的json abi以及hex编码的code,由于太长,太占地方就不放上来了.

这些会在部署以及调用的时候用到.  
下面来通过web3进行合约的部署,读取数据,发起事务以及监听事件的发生.

## 部署合约 ##

部署合约需要创建事务,话费gas,因此相关账户必须事先解锁,web3目前没有api可以解锁账户,需要自己在控制台事先解锁才行.  
首先创建合约,需要制定abi.  
然后就可以部署合约了,这时候需要合约的code,  
部署合约的结果可以通过异步函数来获取,例子已经给出.

## 查询合约 ##

合约部署成功以后,有了地址就可以根据地址来查询合约的状态.  
查询合约状态并不需要发起事务,也不需要花费gas,因此比较简单.

var tokenContract = new web3.eth.Contract(MyTokenABI, '0x6a0dF9E94a41fCd89d8236a8C03f9D678df5Acf9');
    
    tokenContract.methods.name().call(null,function(error,result){
            console.log("contract name "+result);
        })

## 调用合约函数 ##

合约的函数除了指明返回值是constant的以外,都需要发起事务,这时候就需要指定调用者,因为要花费该账户的gas.  
这里调用一下transfer函数.

tokenContract.methods.transfer("0x8c1b2e9e838e2bf510ec7ff49cc607b718ce8401",387).send({from: '0x1a9ec3b0b807464e6d3398a59d6b0a369bf422fa'})
    .on('transactionHash', function(hash){
    })
    .on('confirmation', function(confirmationNumber, receipt){
    })
    .on('receipt', function(receipt){
        // receipt example
        console.log(receipt); //查询这里可以得到结果
    })
    .on('error', console.error); // If a out of gas error, the second parameter is the receipt.

## 监听事件 ##

刚刚调用transfer的时候还会触发合约的事件Transfer,如果程序关注谁给谁进行了转账,那么就可以通过监听该事件.  
通过指定fromBlock,toBlock可以限制事件发生的范围,除了这个还有一个filter参数可以进行更详细的限制,  
如有兴趣可以查询文档[web3文档][web3]

tokenContract.events.Transfer({
        fromBlock: 0,
        toBlock:'latest'
    }, function(error, event){ /*console.log("result:\n"+JSON.stringify(event)); */})
    .on('data', function(event){
        console.log(event); // same results as the optional callback above
    })
    .on('changed', function(event){
        // remove event from local database
    })
    .on('error', console.error);

需要说明的是,这个监听不仅传送历史事件,未来所有事件也会传送.

下面的结果是首先运行程序,会先打印出来刚刚进行的转账.  
然后我在通过其他途径进行转账操作,这时候终端会把新的转账也打印出来.

历史转账:
    { address: '0x6a0dF9E94a41fCd89d8236a8C03f9D678df5Acf9',
      blockNumber: 10680,
      transactionHash: '0x27d5ab9277df504a436b1068697a444d30228584094632f10ab7ba5213a4eccc',
      transactionIndex: 0,
      blockHash: '0xcde734882b0d8cb7a5bf1f7e6d1ccfac5365308de2d7391ce286b45c5546f40b',
      logIndex: 0,
      removed: false,
      id: 'log_2588a961',
      returnValues:
       Result {
         '0': '0x1a9eC3b0b807464e6D3398a59d6b0a369Bf422fA',
         '1': '0x8c1b2E9e838e2Bf510eC7Ff49CC607b718Ce8401',
         '2': '387',
         from: '0x1a9eC3b0b807464e6D3398a59d6b0a369Bf422fA',
         to: '0x8c1b2E9e838e2Bf510eC7Ff49CC607b718Ce8401',
         value: '387' },
      event: 'Transfer',
      signature: '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef',
      raw:
       { data: '0x0000000000000000000000000000000000000000000000000000000000000183',
         topics:
          [ '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef',
            '0x0000000000000000000000001a9ec3b0b807464e6d3398a59d6b0a369bf422fa',
            '0x0000000000000000000000008c1b2e9e838e2bf510ec7ff49cc607b718ce8401' ] } }
    实时监控到的转账
    { address: '0x6a0dF9E94a41fCd89d8236a8C03f9D678df5Acf9',
      blockNumber: 10740,
      transactionHash: '0xb42651720e8b8b64283cbd245aebaa7ad7e3dda58b9887f645ad6957bd7771b8',
      transactionIndex: 0,
      blockHash: '0xcdca97ba5a277e402a93188df03a758c916c37eea0f7498365d227ebd7cb2ee2',
      logIndex: 0,
      removed: false,
      id: 'log_edc5dc68',
      returnValues:
       Result {
         '0': '0x1a9eC3b0b807464e6D3398a59d6b0a369Bf422fA',
         '1': '0x0000000000000000000000000000000000000001',
         '2': '32',
         from: '0x1a9eC3b0b807464e6D3398a59d6b0a369Bf422fA',
         to: '0x0000000000000000000000000000000000000001',
         value: '32' },
      event: 'Transfer',
      signature: '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef',
      raw:
       { data: '0x0000000000000000000000000000000000000000000000000000000000000020',
         topics:
          [ '0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef',
            '0x0000000000000000000000001a9ec3b0b807464e6d3398a59d6b0a369bf422fa',
            '0x0000000000000000000000000000000000000000000000000000000000000001' ] } }

[web3]: http://web3js.readthedocs.io/en/1.0/web3-eth-contract.html