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Approval events on transferFrom and burnFrom (#1524)

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* transferFrom now emits an Approval event, indicating the updated allowance.

* Updated burnFrom to also emit Approval.

* Added notices about the extra Approval events.
This commit is contained in:
Nicolás Venturo
2018-11-29 12:06:47 -03:00
committed by GitHub
parent 6407d7818d
commit 7ef2730506
2 changed files with 31 additions and 4 deletions
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15
contracts/token/ERC20/ERC20.sol
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@ -9,6 +9,10 @@ import "../../math/SafeMath.sol";
* @dev Implementation of the basic standard token.
* https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md
* Originally based on code by FirstBlood: https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
*
* This implementation emits additional Approval events, allowing applications to reconstruct the allowance status for
* all accounts just by listening to said events. Note that this isn't required by the specification, and other
* compliant implementations may not do it.
*/
contract ERC20 is IERC20 {
using SafeMath for uint256;
@ -73,7 +77,9 @@ contract ERC20 is IERC20 {
}
/**
* @dev Transfer tokens from one address to another
* @dev Transfer tokens from one address to another.
* Note that while this function emits an Approval event, this is not required as per the specification,
* and other compliant implementations may not emit the event.
* @param from address The address which you want to send tokens from
* @param to address The address which you want to transfer to
* @param value uint256 the amount of tokens to be transferred
@ -81,6 +87,7 @@ contract ERC20 is IERC20 {
function transferFrom(address from, address to, uint256 value) public returns (bool) {
_allowed[from][msg.sender] = _allowed[from][msg.sender].sub(value);
_transfer(from, to, value);
emit Approval(from, msg.sender, _allowed[from][msg.sender]);
return true;
}
@ -90,6 +97,7 @@ contract ERC20 is IERC20 {
* allowed value is better to use this function to avoid 2 calls (and wait until
* the first transaction is mined)
* From MonolithDAO Token.sol
* Emits an Approval event.
* @param spender The address which will spend the funds.
* @param addedValue The amount of tokens to increase the allowance by.
*/
@ -107,6 +115,7 @@ contract ERC20 is IERC20 {
* allowed value is better to use this function to avoid 2 calls (and wait until
* the first transaction is mined)
* From MonolithDAO Token.sol
* Emits an Approval event.
* @param spender The address which will spend the funds.
* @param subtractedValue The amount of tokens to decrease the allowance by.
*/
@ -165,13 +174,13 @@ contract ERC20 is IERC20 {
* @dev Internal function that burns an amount of the token of a given
* account, deducting from the sender's allowance for said account. Uses the
* internal burn function.
* Emits an Approval event (reflecting the reduced allowance).
* @param account The account whose tokens will be burnt.
* @param value The amount that will be burnt.
*/
function _burnFrom(address account, uint256 value) internal {
// Should https://github.com/OpenZeppelin/zeppelin-solidity/issues/707 be accepted,
// this function needs to emit an event with the updated approval.
_allowed[account][msg.sender] = _allowed[account][msg.sender].sub(value);
_burn(account, value);
emit Approval(account, msg.sender, _allowed[account][msg.sender]);
}
}