I’m very new to solidity programming, and I’m following an old tutorial based on 0.5.0.

I’ve tried to modify the tutorial for a recent version.

I’m trying to create a ECR721 token, and I have code that works. I am however extending from ERC721, ERC721URIStorage and ERC721Enumerable, and I believe there are some issues with methods from those contracts.

Did I correctly resolve these issues, or am I missing some key concepts from the solidity language?

How is super resolved for those methods? It’s not clear to me which supercontract would be used.

pragma solidity ^0.8.26;

import { ERC721 } from "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import { ERC721URIStorage } from "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";
import { ERC721Enumerable } from "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";

contract MemoryToken is ERC721, ERC721URIStorage, ERC721Enumerable {

    mapping (uint256 => address) private _tokenOwner;
    mapping(uint256 tokenId => string) private _tokenURIs;

    constructor() ERC721("Memory Token", "MEMORY") {
    }

    function mint(address _to, string memory _tokenURI) public returns(bool) {
        uint _tokenId = totalSupply() + 1;
        _mint(_to, _tokenId);
        _setTokenURI(_tokenId, _tokenURI);
        return true;
    }

    function tokenURI(uint256 _tokenId) public view override(ERC721, ERC721URIStorage) returns (string memory) {
        return super.tokenURI(_tokenId);
    }

    function supportsInterface(bytes4 interfaceId) public view override(ERC721, ERC721Enumerable, ERC721URIStorage) returns (bool) {
        return
            interfaceId == type(ERC721).interfaceId ||
            interfaceId == type(ERC721URIStorage).interfaceId ||
            interfaceId == type(ERC721Enumerable).interfaceId ||
            super.supportsInterface(interfaceId);
    }

    function _update(address to, uint256 tokenId, address auth) internal override(ERC721, ERC721Enumerable) returns (address) {
        return super._update(to, tokenId, auth);
    }

    function _increaseBalance(address account, uint128 amount) internal override(ERC721, ERC721Enumerable) {
        super._increaseBalance(account, amount);
    }

}