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Improve PullPayment docs (#1965)

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* Improve PullPayment docs

* Reword escrow note

* Update contracts/payment/PullPayment.sol

Co-Authored-By: Francisco Giordano <frangio.1@gmail.com>
(cherry picked from commit 9e19d90cd9)
This commit is contained in:
Nicolás Venturo
2019-10-24 19:04:50 -03:00
committed by Francisco Giordano
parent 7c31b98e6c
commit 21d014d481
1 changed files with 23 additions and 6 deletions
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29
contracts/payment/PullPayment.sol
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@ -3,9 +3,18 @@ pragma solidity ^0.5.0;
import "./escrow/Escrow.sol"; import "./escrow/Escrow.sol";
/** /**
* @title PullPayment * @dev Simple implementation of a
* @dev Base contract supporting async send for pull payments. Inherit from this * https://consensys.github.io/smart-contract-best-practices/recommendations/#favor-pull-over-push-for-external-calls[pull-payment]
* contract and use {_asyncTransfer} instead of send or transfer. * strategy, where the paying contract doesn't interact directly with the
* receiver account, which must withdraw its payments itself.
*
* Pull-payments are often considered the best practice when it comes to sending
* Ether, security-wise. It prevents recipients from blocking execution, and
* eliminates reentrancy concerns.
*
* To use, derive from the `PullPayment` contract, and use {_asyncTransfer}
* instead of Solidity's `transfer` function. Payees can query their due
* payments with {payments}, and retrieve them with {withdrawPayments}.
*/ */
contract PullPayment { contract PullPayment {
Escrow private _escrow; Escrow private _escrow;
@ -15,15 +24,20 @@ contract PullPayment {
} }
/** /**
* @dev Withdraw accumulated balance. * @dev Withdraw accumulated payments.
* @param payee Whose balance will be withdrawn. * @param payee Whose payments will be withdrawn.
*
* Note that _any_ account can call this function, not just the `payee`.
* This means that contracts unaware of the `PullPayment` protocol can still
* receive funds this way, by having a separate account call
* {withdrawPayments}.
*/ */
function withdrawPayments(address payable payee) public { function withdrawPayments(address payable payee) public {
_escrow.withdraw(payee); _escrow.withdraw(payee);
} }
/** /**
* @dev Returns the credit owed to an address. * @dev Returns the payments owed to an address.
* @param dest The creditor's address. * @param dest The creditor's address.
*/ */
function payments(address dest) public view returns (uint256) { function payments(address dest) public view returns (uint256) {
@ -34,6 +48,9 @@ contract PullPayment {
* @dev Called by the payer to store the sent amount as credit to be pulled. * @dev Called by the payer to store the sent amount as credit to be pulled.
* @param dest The destination address of the funds. * @param dest The destination address of the funds.
* @param amount The amount to transfer. * @param amount The amount to transfer.
*
* Funds sent in this way are stored in an intermediate {Escrow} contract, so
* there is no danger of them being spent before withdrawal.
*/ */
function _asyncTransfer(address dest, uint256 amount) internal { function _asyncTransfer(address dest, uint256 amount) internal {
_escrow.deposit.value(amount)(dest); _escrow.deposit.value(amount)(dest);