Not able to access ERC721 OpenZeppelin NFTs from separate contract that inherits NFT contract

Question

I'm creating an NFT that inherits the openzeppelin ERC721 NFT smart contract. I have a contract, BookCreation, that inherits ERC721. This smart contract is where I mint the NFTs in the function mintBook():

    function mintBook(uint256 _bookID, uint256 _editionID) external onlyBookAuthor(_bookID) {
        _tokenIds = _tokenIds + 1;
        books[_bookID]._numMinted = books[_bookID]._numMinted + 1;
        books[_bookID].editions[_editionID]._numMinted = books[_bookID].editions[_editionID]._numMinted + 1;

        emit BookMinted(_tokenIds, _editionID, _bookID, books[_bookID].authorID);
        _safeMint(msg.sender, _tokenIds);
    }

I then have another smart contract, BookStore, that will be the marketplace where you can buy and sell these NFTs.

I have overwritten the ERC721 function ownerOf(uint256 tokenID) as so in my BookCreation contract.

    function ownerOf(uint256 tokenID) public view virtual override returns (address) {
        return super.ownerOf(tokenID);
    }

And then I call this function in BookStore like this (I have also tried super.ownerOf(_tokenID) and ownerOf(_tokenID) in place of (BookCreation.ownerOf(_tokenID)):

    modifier onlyBookOwner(uint256 _tokenID) {
        require(BookCreation.ownerOf(_tokenID) == msg.sender,"This isn't your book!");
        _;
    }

I am running into a problem where, while I can mint a Book in the BookCreation smart contract and see this NFT reflected on the blockchain by calling ownerOf(tokenId) in BookCreation, when I try to call this function in BookStore on the same tokenID by calling BookCreation.ownerOf(tokenId), it is not able to see the NFT that was created.

I am a little unsure about how to be able to read NFTs created in a separate smart contract, any guidance would be helpful!

Other relevant parts of BookCreation class:

import "../node_modules/@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "../node_modules/@openzeppelin/contracts/access/Ownable.sol";

contract BookCreation is ERC721, Ownable {
    uint256 private _tokenIds;
     /**
     * @dev represents a submitted book
     * Along with editions associated with it (initially empty)
     */
    struct Book {
        string title;
        uint256 authorID;
        uint256 _bookID;
        uint256 _numMinted;
        uint256 _numEditions;
        mapping (uint256 => Edition) editions;
    }
    /** @dev Represents specific edition of a specific book
     *    (Advanced Readers Copy, Initial Publishing, 1yr Special Edition, etc)
    */
    struct Edition{
        uint256 _editionID;
        uint256 _bookID;
        uint256 _numMinted;
        string editionName;
    }
    // BookId mapped to the Book it represents
    mapping (uint256 => Book) private books;
    /**
     * @dev Constructs ERC721 "Book" token collection with symbol "TLB"
     */
    constructor() ERC721("Book", "TLB"){
    }

djd djd · Accepted Answer · 2021-08-04T01:44:14

If you could provide more of the code that would be helpful. Otherwise, my guess is something with the super keyword. https://ethereum.stackexchange.com/questions/12920/what-does-the-keyword-super-in-solidity-do

Not able to access ERC721 OpenZeppelin NFTs from separate contract that inherits NFT contract

1 Answers