如何了解interface'；s以太坊区块链的实施和声明之间的联系

我不明白如何将接口声明和实现部分连接在一起

这是一段伪代码，只留下相关的重要部分

ApproveAndCall.sol

    contract ApproveAndCall {
        function receiveApproval(address _sender, uint256 _amount, address _addressOfToken, bytes _extraData) external {
            emit ReceiveApproval(_sender, _amount, _addressOfToken, _extraData);
        }
    }

TokenERC20.sol
    interface tokenRecipient { 
      function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external; 
    }

    contract TokenERC20 is Pausable {
        function approveAndCall(address _spender, uint256 _value, bytes _extraData) public noReentrancy returns (bool success) {
                tokenRecipient spender = tokenRecipient(_spender);
                spender.receiveApproval(msg.sender, _value, this, _extraData);
        }
    }

正如您所看到的，接口“tokenRecipient”是在TokenERC20.sol中声明的 名为“spender”的令牌接收者将调用函数“receiveApproval”

但TokenERC20智能合约如何知道真正的“接受批准”，即“挥霍者”

我认为这似乎与地址或其他东西没有任何联系

---

这两个智能合约都已部署在rinkeby testnet上。这个接口只是为了方便起见，所以您可以轻松地调用接口方法。您可以将任何智能合约地址强制转换到此接口，即使它们不是此接口的实例

例如，如果我对您的示例进行以下更改：

批准并调用.sol

contract ApproveAndCall {
    function receiveApproval(address _sender, uint256 _amount, address _addressOfToken, bytes _extraData) external {
        emit ReceiveApproval(_sender, _amount, _addressOfToken, _extraData);
    }
}

contract ApproveAndCall2 {
    function() public {
        emit Fallback(msg.data);
    }
}

interface tokenRecipient { 
  function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external; 
}

contract TokenERC20 is Pausable {
    function approveAndCall(address _spender, uint256 _value, bytes _extraData) public noReentrancy returns (bool success) {
            tokenRecipient spender = tokenRecipient(_spender);
            spender.receiveApproval(msg.sender, _value, this, _extraData);
    }
}

TokenERC20.sol

contract ApproveAndCall {
    function receiveApproval(address _sender, uint256 _amount, address _addressOfToken, bytes _extraData) external {
        emit ReceiveApproval(_sender, _amount, _addressOfToken, _extraData);
    }
}

contract ApproveAndCall2 {
    function() public {
        emit Fallback(msg.data);
    }
}

interface tokenRecipient { 
  function receiveApproval(address _from, uint256 _value, address _token, bytes _extraData) external; 
}

contract TokenERC20 is Pausable {
    function approveAndCall(address _spender, uint256 _value, bytes _extraData) public noReentrancy returns (bool success) {
            tokenRecipient spender = tokenRecipient(_spender);
            spender.receiveApproval(msg.sender, _value, this, _extraData);
    }
}

如果

批准和调用

合同的地址将用作

\u spender

参数，它将按预期工作，因为智能合同中实际上定义了相应的函数，因此调用了

接收批准

但是，如果将

批准和调用2

合同的地址用作

\u spender

参数，则会调用“回退函数”，因为

批准和调用2

合同上不存在

接收批准

函数。

msg.data

变量包含此函数调用的编码调用数据（函数名、参数值等）