So, I'm trying to implement openzeppelin ERC721Enumerable contract. I want to override _beforeTokenTransfer method. Because it was a Hook, I have to call super method like this
function _beforeTokenTransfer( address from, address to, uint256 tokenId ) internal virtual override { super._beforeTokenTransfer(from, to, tokenId); // some requirement require(someRequirement(_msgSender()), 'MyERC721: Sender has not met the requirement to proceed') // some stuff } The problem is, inside _beforeTokenTransfer of ERC721Enumerable, there are some changing state variables. I am worried that when my method reverted, the state variables there are changed before are not going back to their previous state. Usually, something like this will happened
>>> class SomeClass: ... def __init__(self): ... self.state = 0 ... def change_state(self, x): ... self.state += x ... raise Exception('method reverted') >>> an_instance = SomeClass() >>> an_instance.state 0 >>> an_instance.change_state(10) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 6, in change_state Exception: method reverted >>> an_instance.state 10 The state variable inside SomeClass is changed because the exception is raised after the state changed. Does this also valid for SmartContract? How does SmartContract handle changing state before exception is raised?
