// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;

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;

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

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

    // 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);
    }

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

2. safemint
   • to:自己address, uri: https://alanhc.github.io/nft/opensea-example.json 就可以在 testnet opensea看到 其實也可以不用一個一個設置：可以直接設置baseuri :https://ethereum.stackexchange.com/questions/122404/best-way-to-set-metadata-in-erc721-contract-on-production

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;

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

contract MyToken is ERC1155, Ownable {
    uint256 public constant Rock = 1;
    uint256 public constant Paper = 2;
    uint256 public constant Scissors = 3;
    constructor() ERC1155("https://alanhc.github.io/nft/erc-1155/{id}.json") {
        _mint(msg.sender, Rock, 1, "");
        _mint(msg.sender, Paper, 1, "");
        _mint(msg.sender, Scissors, 1, "");
    }

    function setURI(string memory newuri) public onlyOwner {
        _setURI(newuri);
    }

    function mint(address account, uint256 id, uint256 amount, bytes memory data)
        public
        onlyOwner
    {
        _mint(account, id, amount, data);
    }

    function mintBatch(address to, uint256[] memory ids, uint256[] memory amounts, bytes memory data)
        public
        onlyOwner
    {
        _mintBatch(to, ids, amounts, data);
    }
}
solidity

註記：mint data要設定 0x0000000000000000000000000000000000000000000000000000000000000000