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");
}
posted on
2018-02-28 16:55
北京涛子 阅读(
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转载于:https://www.cnblogs.com/liujitao79/p/8484539.html
