Mastering Blockchain Programming with Solidity

The _clearApproval internal function

_clearApproval() is a private function that is used by the ERC721 implementation itself to clear any approvals given previously for the provided tokenId variable. The function takes the tokenId for which the approvals should be cleared. The function is defined as follows:

function _clearApproval(uint256 tokenId) private {    if (_tokenApprovals[tokenId] != address(0)) {        _tokenApprovals[tokenId] = address(0);    }}

As it is a private function, it cannot be accessed from the inherited contracts. However, this is only used by the ERC721 implementation itself. The function first verifies that the current approval address is not address(0); if not, it clears out the approval by setting it to address(0).

Initially, ...