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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event Withdrawn(address indexed payee, uint256 weiAmount); mapping(address =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* @dev Stores the sent amount as credit to be withdrawn.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* @param _payee The address whose funds will be withdrawn and transferred to.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deposits_[_payee] = 0; _payee.transfer(payment); emit Withdrawn(_payee, payment);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.; 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.; 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.; 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());
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.; 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 = ;
uint256 public totalReleased = ; 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 > ); for (uint256 i = ; 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] > ); 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 != );
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());
require(_shares > );
require(shares[_payee] == ); 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
