ERC721 mint with multiple URIs

Support Contracts
1

Hi, I was thinking of a case where each uri is set upon mint.
The mint function takes in an amount to mint and a corresponding number of uri in an array.
Then as the tokenID is increased, the current tokenID is is set to the uri in the array.
User mints 2 items, token id of first item is 1 and second item is 2
The uri given as [uri1, uri2] is then assigned, 1-uri1 and 2 to uri2
When the tokenURI is called, with tokenID argument, instead of concatenating a base uri with tokenid, it returns the uri from the mapping perhaps.
(Id=> uri) token
TokenURI(1) returns
token[1] =uri1

I wonder if it’s possible with the current protocols in place for ERC721

Thank you for your opinions

2

This should be possible and relatively simple to put together. You should give this a try and write the mint function that you need, then share it here.

Take a look at Contracts Wizard and choose Mintable + URI Storage. You should change safeMint so it takes an array of URIs instead of a single one, and then inside the function add a for loop.

3 
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.2;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Counters.sol";

contract MyToken is ERC721, ERC721URIStorage, Ownable {
    using Counters for Counters.Counter;
    Counters.Counter private _tokenIdCounter;
    uint256 _tokenId = 1;

    constructor() ERC721("MyToken", "MTK") {}

    function safeMint(address to, string[] memory uri) public onlyOwner {
         for(uint8 i = 0; i<uri.length; i++){
        _tokenId = _tokenIdCounter.current();      
        _tokenIdCounter.increment();
        _safeMint(to, _tokenId);
        _setTokenURI(_tokenId, uri[i]);
        }
    }

    // The following functions are overrides required by Solidity.

    function _burn(uint256 tokenId) internal override(ERC721, ERC721URIStorage) {
        super._burn(tokenId);
    }

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

Thank you so much!
this works pretty well, although I tried to initialize the token id as one, so the counter starts from one but it doesn't work that way. Is there a way i can make it start counting from 1?

4

Include _tokenIdCounter.increment() in the constructor.

1 Like
5

It works! I'll give you credit in the smart contract comment haha. Thank you so much

1 Like
6

I have written something similar but it does not work, does anyone has any insights?

I have added a bulkMint function which takes a string array and in the function I will iterate the string array and call safeMint multiple times.
I found that if I pass a string array with only 1 element, it works. However, if there are more than 1 strings, it throws error.
Succeeded tx: https://mumbai.polygonscan.com/tx/0xf25edc6187f47f88493063c004487f35261360f8e0015d480573b15bff800056
Failed tx: https://mumbai.polygonscan.com/tx/0xeac51304c5a553dd3569663192fdca433e8f4febedf30a84d617c570cdc580ed

function bulkMint(address to, string[] memory uris)
        public
        onlyRole(MINTER_ROLE)
    {
        for (uint8 i = 0; i < uris.length; i++) {
            safeMint(to, uris[i]);
        }
    }

    function safeMint(address to, string memory uri)
        public
        onlyRole(MINTER_ROLE)
    {
        uint256 tokenId = _tokenIdCounter.current();
        _tokenIdCounter.increment();
        _safeMint(to, tokenId);
        _setTokenURI(tokenId, uri);
    }

my contract:

7

That error looks really strange! The code looks good to me. Have you tested it locally with Hardhat?

8

Shouldn't the safeMint() be internal, if it only gets called by bulkMint?

(I'm a newbie, so don't take my words for the truth!)

Have you found an answer? I'm trying to mint more than one NFT in one contract (with a list of URIs like you) and trying to figure out how to get it done properly :slight_smile:

9

In this case it doesn't seem to make a difference. There is no real downside to making it public, only minimal overhead to bytecode size and runtime cost.

1 Like
10

Thank you for the information :slight_smile: