Mastering Blockchain Programming with Solidity

Approved address mapping kept in _tokenApprovals

An owner of an ERC721 token can give approval to another address. Once approval is given, another address can transfer the approved ERC721 token from the owner's wallet. Let's understand how these approvals are maintained in the contract.

The _tokenApprovals mapping is used to find the approver's address for a given NFT ID. _tokenApprovals is a mapping from uint256 to address, which stores the mapping for the NFT ID to the approved spender's address. In the code, it's defined as follows:

mapping (uint256 => address) private _tokenApprovals;function getApproved(uint256 tokenId) public view returns (address) {    require(_exists(tokenId));    return _tokenApprovals[tokenId];}

The mapping variable is ...