Create NFT on Ethereum Testnet

This implemtation is reference from 2021 快速建立 ERC721 標準智能合約並且 Mint NFT

Set up

Create a empty directory mkdir NFT_EXAMPLE
install npm npm init
To use the standard ERC-721 smart contract, you can reference by openzeppelin provide contract, therefore, please install @openzeppelin/contracts module npm install --save @openzeppelin/contracts

Deploying your NFT smart contract on Ethereum testnet

It is recommanded to use the Ethereum smart contract IDE Remix

In order to manage your local directory, connect the remix IDE to local host

install remix npm module globoly npm install -g @remix-project/remixd
check if installation successed remixd -v
link the remix and local directory remixd -s <absolute-path-to-the-shared-folder> --remix-ide https://remix.ethereum.org/
open remix can change the workspace to localhost and you can see check the local directory linked
the create the contracts directory
add your NFT smart contract file <name>.sol, take following solidity code as example
- change the argument in ERC721PresetMinterPauserAutoId function
  - NFT NAME
  - Token code
  - MetaData URI (The share URI of created folder, remember to add \ at last)

// @openzeppelin v3.2.0
pragma solidity ^0.8.0;
import "../node_modules/@openzeppelin/contracts/token/ERC721/presets/ERC721PresetMinterPauserAutoId.sol";
contract veryBig is ERC721PresetMinterPauserAutoId {
    constructor() public
    ERC721PresetMinterPauserAutoId("veryBig", "VB", "https://ipfs.io/ipfs/QmVwDck8FSJ41zpWMoe4KoZMfqN1gdMcqNpiLX4R8LtBru/")  
    {}
    //NFT NAME, Token code, MetaData URI
    // This allows the minter to update the tokenURI after it's been minted.
    // To disable this, delete this function.
    function setTokenURI(uint256 tokenId, string memory tokenURI) public {
        require(hasRole(MINTER_ROLE, _msgSender()), "web3 CLI: must have minter role to update tokenURI");
        setTokenURI(tokenId, tokenURI);
    }
}

Setting up MetaData URI

Using IPFS storage. The reason is the we need to storage the docment in ad safety way

Download ipfs desktop
Open ipfs desktop, the import a new folder
Import the image (or data) represent the NFT
Import the metadata.json file, rename it to 0 (since the NFT token will mint in order from 0)
- You can change the tile, name, and imageUrl
- The imageUrl should be the share link of image in IPFS

{
    "title": "Shun Metadata",
    "name": "shunan photo 0",
    "imageUrl": "https://ipfs.io/ipfs/QmPE3dpYehnRcQqcPWHH5AjgxS76ivhwAFik2KiaAUoAyF?filename=shun.jpeg",
    "type": "object",
    "properties": {
        "name": {
            "type": "string",
            "description": "Identifies the asset to which this NFT represents"
        },
        "description": {
            "type": "string",
            "description": "Describes the asset to which this NFT represents"
        },
        "uri": {
            "type": "string",
            "description": "A URI pointing to a resource"
        },
        "custom_attributes": {
            "type": "object",
            "description": "a nested json"
        }
    }
}

Deploy the NFT contract

compile
deploy
- you have to download MetaMask extension and create and account
  - you can get eth by faucet
- Choose the Rinkeby Test Network
- Then deploy