solidity msg.sender.transfer发送给谁_msg.sender.trans()fer是什么意思

发送给调用者自己，表示将该合约中的自己应有的以太坊退款到发送者自己的账户

address.transfer(amount)

转账一定数量（以wei为单位）的以太币到指定的地址，遇到任何错误都将抛出异常。我们在Faucet例子中使用过这个方法，针对的是msg.sender这个地址，即msg.sender.transfer

精通以太坊8：智能合约与Solidity（2） | 码农家园精通以太坊8：智能合约与Solidity（2）8.1使用Solidity进行编程有关Solidity的完整文档可以在这里访问：https://solidity.readthedocs.io/en/latest。8.2数据...https://www.codenong.com/cs105234539/

如：weth源码

pragma solidity ^0.4.18;
 
contract WETH9 {
    string public name     = "Wrapped Ether";
    string public symbol   = "WETH";
    uint8  public decimals = 18;
 
    event  Approval(address indexed src, address indexed guy, uint wad);
    event  Transfer(address indexed src, address indexed dst, uint wad);
    event  Deposit(address indexed dst, uint wad);
    event  Withdrawal(address indexed src, uint wad);
 
    mapping (address => uint)                       public  balanceOf;
    mapping (address => mapping (address => uint))  public  allowance;
 
    function() public payable {
        deposit();
    }
    function deposit() public payable {
        balanceOf[msg.sender] += msg.value;
        Deposit(msg.sender, msg.value);
    }
    function withdraw(uint wad) public {
        require(balanceOf[msg.sender] >= wad);
        balanceOf[msg.sender] -= wad;
        msg.sender.transfer(wad);
        Withdrawal(msg.sender, wad);
    }
 
    function totalSupply() public view returns (uint) {
        return this.balance;
    }
 
    function approve(address guy, uint wad) public returns (bool) {
        allowance[msg.sender][guy] = wad;
        Approval(msg.sender, guy, wad);
        return true;
    }
 
    function transfer(address dst, uint wad) public returns (bool) {
        return transferFrom(msg.sender, dst, wad);
    }
 
    function transferFrom(address src, address dst, uint wad)
        public
        returns (bool)
    {
        require(balanceOf[src] >= wad);
 
        if (src != msg.sender && allowance[src][msg.sender] != uint(-1)) {
            require(allowance[src][msg.sender] >= wad);
            allowance[src][msg.sender] -= wad;
        }
 
        balanceOf[src] -= wad;
        balanceOf[dst] += wad;
 
        Transfer(src, dst, wad);
 
        return true;
    }
}