How do you set max amount of NFTs a wallet can mint?

Question

contract xyz is ERC721, ERC721Enumerable, ERC721URIStorage, Ownable {
    using Counters for Counters.Counter;

    Counters.Counter private _tokenIdCounter;
    
    uint256 public constant maxSupply = 9999;
    uint256 public constant userLimit = 1;
    mapping(address => uint) public walletMints;

    constructor() ERC721("xyz", "xyz") {}

    function safeMint(address to, string memory uri) public onlyOwner {
        require(_tokenIdCounter.current() <= maxSupply, "I'm sorry we reached the cap");
        uint256 tokenId = _tokenIdCounter.current();
        _tokenIdCounter.increment();
        _safeMint(to, tokenId);
        _setTokenURI(tokenId, uri);
    }

I have the contract to check and map the wallets address, but I don't know how to write into the mint function how to limit the wallet to only mint 1 nft.

My current guess is it's something along the lines of "require(walletMints[msg.sender] <= userLimit" ?

Any help is appreciated!

Answer 1

contract xyz is ERC721, ERC721Enumerable, ERC721URIStorage, Ownable {
    using Counters for Counters.Counter;

    Counters.Counter private _tokenIdCounter;
    
    uint256 public constant maxSupply = 9999;
    uint256 public constant userLimit = 1;
    mapping(address => uint) public walletMints;
    

    constructor() ERC721("xyz", "xyz") {}

    function safeMint(address to, string memory uri) public onlyOwner {
        require(_tokenIdCounter.current() <= maxSupply, "I'm sorry we reached the cap");
       require(walletMints[msg.sender] <= userLimit, "I'm sorry only one NFT per user");
        uint256 tokenId = _tokenIdCounter.current();
        _tokenIdCounter.increment();
        _safeMint(to, tokenId);
        _setTokenURI(tokenId, uri);
    }
    ```

Answer 2

you should use function 'balanceOf' or 'balances' state variable. (they return The number of NFTs owned by an address).

contract xyz is ERC721, ERC721Enumerable, ERC721URIStorage, Ownable {
using Counters for Counters.Counter;

Counters.Counter private _tokenIdCounter;

uint256 public constant maxSupply = 9999;
uint256 public constant userLimit = 1;
mapping(address => uint) public walletMints;

constructor() ERC721("xyz", "xyz") {}

function safeMint(address to, string memory uri) public onlyOwner {
    require(_tokenIdCounter.current() <= maxSupply, "I'm sorry we reached the cap");
    require(balanceOf(to) <= userLimit ,'user limit error maessage')
    uint256 tokenId = _tokenIdCounter.current();
    _tokenIdCounter.increment();
    _safeMint(to, tokenId);
    _setTokenURI(tokenId, uri);
}

Answer 3

using BalanceOf state variable is not an answer since a user can transfer that nft to another account and mint again. There is not any solution to this even if you do something like this:

 uint totalPerWallet = 2;
 struct QtyPerUser{
        address userAddr;
        uint256 balance;
    }

    mapping(address =>QtyPerUser) public QtyPerUserMap ;
    ...  
    require(totalPerWallet >= QtyPerUserMap[msg.sender].balance,"Cannot mint more than Qty allowed");

A user can create many wallet addresses using a bot ahha.