Lesson 14: randomIpfsNft.test.js question

[YuraH99]

Inside the "fulfillRandomWords" test, there is this line of code:

const tokenUri = await randomIpfsNft.tokenURI("0")

For me, it returns this via console log: ipfs://QmZYmH5iDbD6v3U2ixoVAjioSzvWJszDzYdbeCLquGSpVm.
My question is, in the contract there is no function called tokenURI, so what is it that we are calling here? Is it coming from the ERC721 extension?

[krakxn]

Yes, we are calling via @openzeppelin/contracts/token/erc721/extensions/erc721uristorage.sol. And inside that contract, specifically, the following code is what we are using here:

Context:

/**
     * @dev See {IERC721Metadata-tokenURI}.
     */
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        _requireMinted(tokenId);

        string memory _tokenURI = _tokenURIs[tokenId];
        string memory base = _baseURI();

        // If there is no base URI, return the token URI.
        if (bytes(base).length == 0) {
            return _tokenURI;
        }
        // If both are set, concatenate the baseURI and tokenURI (via abi.encodePacked).
        if (bytes(_tokenURI).length > 0) {
            return string(abi.encodePacked(base, _tokenURI));
        }

        return super.tokenURI(tokenId);
    }

Hope this answers your query!

[YuraH99]

I see, thank you very much!

[krakxn]

No problem, all the best.