openzeppelin-solidity/contracts的代码学习——payment
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payment - A collection of smart contracts that can be used to manage payments through escrow arrangements, withdrawals, and claims. Includes support for both single payees and multiple payees.(这个是不是就是token中withdrawl的来源,要好好看看,在博客的the security of smart有写)
临时账户:其实就是一个映射,在下面例子即deposits_,存储某address应该从合约中取出的钱数
下面这里的代码是openzepplin中写的有关实现临时账户的标准,值得学习,我们学习类似cryptopunks的代码的时候就发现他们是这么写的
https://github.com/OpenZeppelin/openzeppelin-solidity/tree/master/contracts/payment
Escrow.sol
pragma solidity ^0.4.23;
import "../math/SafeMath.sol";
import "../ownership/Ownable.sol";
/**
* @title Escrow
* @dev Base escrow contract, holds funds destinated to a payee until they
* withdraw them. The contract that uses the escrow as its payment method
* should be its owner, and provide public methods redirecting to the escrow‘s
* deposit and withdraw.
*/
contract Escrow is Ownable {
using SafeMath for uint256;
event Deposited(address indexed payee, uint256 weiAmount);
event Withdrawn(address indexed payee, uint256 weiAmount);
mapping(address => uint256) private deposits_;
//得到临时账户中的余额
function depositsOf(address _payee) public view returns (uint256) {
return deposits_[_payee];
}
/**
* @dev Stores the sent amount as credit to be withdrawn.
* @param _payee The destination address of the funds.
*/
//往临时账户中存钱,因为声明为payable,所以调用该函数的address通过将msg.value数量的金额传给了合约地址,并同时将数额写到临时账户deposits_上
function deposit(address _payee) public onlyOwner payable {
uint256 amount = msg.value;//为什么不直接用msg.value进行add运算,是这样更安全吗??????
deposits_[_payee] = deposits_[_payee].add(amount);//为了安全,不使用+来直接运算,而是使用SafeMath.sol中的函数
emit Deposited(_payee, amount);
}
/**
* @dev Withdraw accumulated balance for a payee.
* @param _payee The address whose funds will be withdrawn and transferred to.
*/
//从合约地址中取出临时账户上的所有钱,并将临时账户上的数额清零
function withdraw(address _payee) public onlyOwner {
uint256 payment = deposits_[_payee];
assert(address(this).balance >= payment);//原本是this.balance来得到当前账户地址上的余额??????,address(this)就是是显示转换成合约地址为address类型
deposits_[_payee] = 0;
_payee.transfer(payment);
emit Withdrawn(_payee, payment);
}
}
疑惑address(this).balance的解决,(这里的this代表的是合约的地址):
pragma solidity ^0.4.24;
contract Get{
//查询当前的余额 function getBalance() public view returns(uint){ return this.balance; }
event SendEvent(address to, uint value, bool result);
//使用send()发送ether,观察会触发fallback函数
function sendEther() public{
bool result = this.send(1);
emit SendEvent(this, 1, result);
}
当想要使用this.balance这么写得到账户的余额时,remix编译中会报警告:
Warning:Using contract member "balance" inherited from the address type is deprecated.Convert the contract to "address" type to access the member,for example use "address(contract).balance" instead.
除此之外,使用this.send也是会报相似的警告:
Warning:Using contract member "send" inherited from the address type is deprecated.Convert the contract to "address" type to access the member,for example use "address(contract).send" instead.
这就是this.balance为什么改为address(this).balance的原因,在这里this.send也要改为address(this).send
PullPayment.sol
pragma solidity ^0.4.24; import "./Escrow.sol"; /** * @title PullPayment * @dev Base contract supporting async send for pull payments. Inherit from this * contract and use asyncTransfer instead of send or transfer. */ contract PullPayment { Escrow private escrow; constructor() public { escrow = new Escrow(); } /** * @dev Withdraw accumulated balance, called by payee. */ //取钱 function withdrawPayments() public { address payee = msg.sender; escrow.withdraw(payee); } /** * @dev Returns the credit owed to an address. * @param _dest The creditor‘s address. */ //查余额 function payments(address _dest) public view returns (uint256) { return escrow.depositsOf(_dest); } /** * @dev Called by the payer to store the sent amount as credit to be pulled. * @param _dest The destination address of the funds. * @param _amount The amount to transfer. */ //向临时账户中存钱 function asyncTransfer(address _dest, uint256 _amount) internal { escrow.deposit.value(_amount)(_dest);//形如someAddress.call.value()() ,因为deposit是payable的,value(_amount)相当于{value:_amount} } }
contracts/payment/ConditionalEscrow.sol
就是当某条件允许时才能够将临时账户中的钱取出
该函数为abstract函数
pragma solidity ^0.4.23; import "./Escrow.sol"; /** * @title ConditionalEscrow * @dev Base abstract escrow to only allow withdrawal if a condition is met. */ contract ConditionalEscrow is Escrow { /** * @dev Returns whether an address is allowed to withdraw their funds. To be * implemented by derived contracts. * @param _payee The destination address of the funds. */ function withdrawalAllowed(address _payee) public view returns (bool); function withdraw(address _payee) public { require(withdrawalAllowed(_payee));//只有满足情况了才能withdraw,下面即实现例子RefundEscrow.sol super.withdraw(_payee); } }
contracts/payment/RefundEscrow.sol
当账户状态为Refunding时,存钱的人能把存的钱取回
当账户状态为Closed时,受益人才能把账户中的钱取出
pragma solidity ^0.4.23; import "./ConditionalEscrow.sol"; import "../ownership/Ownable.sol"; /** * @title RefundEscrow * @dev Escrow that holds funds for a beneficiary(收益人), deposited from multiple parties. * The contract owner may close the deposit period, and allow for either withdrawal * by the beneficiary, or refunds to the depositors. */ contract RefundEscrow is Ownable, ConditionalEscrow { enum State { Active, Refunding, Closed } event Closed(); event RefundsEnabled(); State public state; address public beneficiary; /** * @dev Constructor. * @param _beneficiary The beneficiary of the deposits. */ constructor(address _beneficiary) public {//声明受益人,此时账户状态为Active require(_beneficiary != address(0)); beneficiary = _beneficiary; state = State.Active; } /** * @dev Stores funds that may later be refunded. * @param _refundee The address funds will be sent to if a refund occurs. */ function deposit(address _refundee) public payable {//往账户存钱 require(state == State.Active); super.deposit(_refundee);//使用的是super,即父合约而不是this本合约 } /** * @dev Allows for the beneficiary to withdraw their funds, rejecting * further deposits. */ function close() public onlyOwner {//当账户状态为Closed,就不能再往里面存钱了,只能受益人取钱 require(state == State.Active); state = State.Closed; emit Closed(); } /** * @dev Allows for refunds to take place, rejecting further deposits. */ function enableRefunds() public onlyOwner { require(state == State.Active); state = State.Refunding; emit RefundsEnabled(); } /** * @dev Withdraws the beneficiary‘s funds. */ function beneficiaryWithdraw() public {//受益人取钱 require(state == State.Closed); beneficiary.transfer(address(this).balance); } /** * @dev Returns whether refundees can withdraw their deposits (be refunded). */ function withdrawalAllowed(address _payee) public view returns (bool) {//当账户状态为Refunding时,存钱的人能把存的钱取回 return state == State.Refunding; } }
contracts/payment/SplitPayment.sol
付款人能够根据自己在该合约生成时付的钱生成的股份shares[payee]占总股份的比例来要求合约返还自己的钱
pragma solidity ^0.4.24; import "../math/SafeMath.sol"; /** * @title SplitPayment * @dev Base contract that supports multiple payees claiming funds sent to this contract * according to the proportion they own. */ contract SplitPayment { using SafeMath for uint256; uint256 public totalShares = 0; uint256 public totalReleased = 0; mapping(address => uint256) public shares;//payee所拥有的股份 mapping(address => uint256) public released;//合约已经还给payee的钱 address[] public payees; /** * @dev Constructor */ constructor(address[] _payees, uint256[] _shares) public payable { require(_payees.length == _shares.length); require(_payees.length > 0); for (uint256 i = 0; i < _payees.length; i++) {//在该合约创建的时候_payee就都加到该合约中了,比例也是早就算好的 _addPayee(_payees[i], _shares[i]); } } /** * @dev payable fallback */ function () external payable {} /** * @dev Claim your share of the balance. */ function claim() public { address payee = msg.sender; require(shares[payee] > 0); uint256 totalReceived = address(this).balance.add(totalReleased);//就是合约还回去的钱totalReleased+现在合约中有的钱 = 合约总共收到的钱 uint256 payment = totalReceived.mul( //等价于((totalReceived*(shares[payee]/totalShares))-released[payee]),就是通过比例算出本payee发给该合约的钱-之前还的钱released[payee] = 还需要还的钱payment shares[payee]).div( totalShares).sub( released[payee] ); require(payment != 0); assert(address(this).balance >= payment);//合约中现在还有的钱要大于payment才能把钱给payee released[payee] = released[payee].add(payment); totalReleased = totalReleased.add(payment); payee.transfer(payment); } /** * @dev Add a new payee to the contract. * @param _payee The address of the payee to add. * @param _shares The number of shares owned by the payee. */ function _addPayee(address _payee, uint256 _shares) internal { require(_payee != address(0)); require(_shares > 0); require(shares[_payee] == 0); payees.push(_payee); shares[_payee] = _shares; totalShares = totalShares.add(_shares); } }
??:Add a leading underscore to internal and private functions,要在internal and private函数的名字前加下划线
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