solidity语言11

函数修饰符

pragma solidity ^0.4.11;

contract owned {
    address owner;

    // 构造函数
    function owned() public { 
        owner = msg.sender;
    }

    // 此合约定义的函数修饰符不使用，用于衍生的合约
    modifier onlyOwner {
        require(msg.sender == owner);
        _; // 引用的函数体部分
    }
}

contract mortal is owned {
    function close() public onlyOwner {
        selfdestruct(owner);
    }
}

    /* 相当于
    function close() public onlyOwner {
        require(msg.sender == owner);
        selfdestruct(owner);
    }
    */

contract priced {
    modifier costs(uint price) {
        if (msg.value >= price) {
            _;
        }
    }
}

// 继承合约priced，owned
contract Register is priced, owned {
    mapping (address => bool) registeredAddresses;
    uint price;
    
    function Register(uint initialPrice) public { 
        price = initialPrice; 
    }

    // 这里使用关键字payable很重要，否则函数将自动拒绝所有以太的转帐
    function register() public payable costs(price) {
        registeredAddresses[msg.sender] = true;
    }

    /* 相当于
    function register() public payable costs(price) {
        if (msg.value >= price) {
            registeredAddresses[msg.sender] = true;
        }
    }
    */

    function changePrice(uint _price) public onlyOwner {
        price = _price;
    }

    /* 相当于
    function changePrice(uint _price) public onlyOwner {
        require(msg.sender == owner);
        price = _price;
    }
    */
}

contract Mutex {
    bool locked;
    
    modifier noReentrancy() {
        require(!locked);
        locked = true;
        _;
        locked = false;
    }

    function f() public noReentrancy returns (uint) {
        require(msg.sender.call());
        return 7;
    }

    /* 相当于
    function f() public noReentrancy returns (uint) {
        require(!locked);
        locked = true;

        require(msg.sender.call());
        return 7;
        
        locked = false;
    }
    */
}

常量

pragma solidity ^0.4.0;

contract C {
    uint constant NUMER = 32 ** 22 + 8;
    string constant TEXT = "abc";
    bytes32 constant MYHASH = keccak256("abc");
}