Implementing ERC-1155 contract on the fly

Question

I want to implement an ERC-1155 token to represent ownership of videos. Creating such a contract is relatively easy:

import "@openzeppelin/contracts/token/ERC1155/ERC1155.sol";

contract MyVideos is ERC1155 {
    uint256 public constant Video1 = 0;
    uint256 public constant Video2 = 1;
    uint256 public constant Video3 = 2;

    constructor() public ERC1155("https://video/api/item/{id}.json") {
        _mint(msg.sender, Video1, 100, "IPFS hash");
        _mint(msg.sender, Video2, 1000, "IPFS hash");
        _mint(msg.sender, Video3, 1, "IPFS hash");
    }
}

However, what I have no idea how to do is to create such ERC-1155 tokens dynamically and on the fly. Specifically, how would I add Video3 with 10000 tokens

(_mint(msg.sender, Video4, 10000, "IPFS hash");

But how do I add this new token after the contract MyVideos is already created?

I would really appreciate any help you can give me.

Many thanks!

Answer 1

You need to write a public wrapper function for the _mint function. Since this function is internal, it can only be called from within the context of the contract itself.

Something like:

function addNewVideo(uint VideoN, uint ntokens, bytes memory IPFS_hash) public {
    _mint(msg.sender, VideoN, ntokens, IPFS_hash);
}

Answer 2

this is done using "Factory" approach. You have a factory contract and it does this for you. Take a look at uniswap v2 contract factory:

function createPair(address tokenA, address tokenB) external returns (address pair) {
        require(tokenA != tokenB, 'UniswapV2: IDENTICAL_ADDRESSES');
        (address token0, address token1) = tokenA < tokenB ? (tokenA, tokenB) : (tokenB, tokenA);
        require(token0 != address(0), 'UniswapV2: ZERO_ADDRESS');
        require(getPair[token0][token1] == address(0), 'UniswapV2: PAIR_EXISTS'); // single check is sufficient
        bytes memory bytecode = type(UniswapV2Pair).creationCode;
        bytes32 salt = keccak256(abi.encodePacked(token0, token1));
        assembly {
            pair := create2(0, add(bytecode, 32), mload(bytecode), salt)
        }
        IUniswapV2Pair(pair).initialize(token0, token1);
        getPair[token0][token1] = pair;
        getPair[token1][token0] = pair; // populate mapping in the reverse direction
        allPairs.push(pair);
        emit PairCreated(token0, token1, pair, allPairs.length);
    }

https://github.com/Uniswap/uniswap-v2-core/blob/master/contracts/UniswapV2Factory.sol