如何在 Solidity 中声明常量

Question

我对 Solidity 和智能合约非常陌生，非常感谢一些帮助。我正在遵循教程，这就是他们使用的确切代码。但是当我编译代码时，我收到此错误：

ParserError：预期的主表达式。地址公共常量​​批准者 = ;

pragma solidity ^0.6.0;

contract ApprovalContract {

    address public sender;
    address public receiver;
    address public constant approver = ;

    function deposit(address _receiver) external payable {
        require(msg.value > 0);
        sender = msg.sender;
        receiver = _receiver;
    }

    function viewApprover() external pure returns(address) {
        return(approver);
    }

    function approve() external {
        require(msg.sender == approver);
        receiver.transfer(address(this).balance);
    }
}

Answer 1

常量需要初始化

address public constant approver = YOURADDRESS;