How can I get a list of NFTs that I have minted?

Question

I am building Social Media for NFT.

I would like to get a list of NFTs minted in the past by a particular user in Ethereum and Polygon Chain. It does not have to be currently held. Is there a good way to do this?

Answer 1

You write this function in your smart contract

function getOwnedNfts() public view returns(NftItem[] memory){
    uint ownedItemsCount=ERC721.balanceOf(msg.sender);
    NftItem[] memory items= new NftItem[](ownedItemsCount);
    for (uint i=0; i<ownedItemsCount; i++){
      // when user owns a token, I keep track of them in mapping instead of array
     // It is saving the tokens of user in order
      uint tokenId=tokenOwnerByIndex(msg.sender, i);
      NftItem storage item=_idToNftItem[tokenId];
      items[i]=item;
    }
    return items;
  }

• this is ERC721.balanceOf

  function balanceOf(address owner) public view virtual override returns (uint256) {
            require(owner != address(0), "ERC721: balance query for the zero address");
            return _balances[owner];
        }
  

When you call _mint function, the address who has minted is added to _balance

• this is tokenOwnerByIndex

   function tokenOwnerByIndex(address owner,uint index) public view returns(uint){
        require(index<ERC721.balanceOf(owner), "Index out of bounds");
        return _ownedTokens[owner][index];
      }
  

_ownedTokens is a mapping:

//{address:{1:tokenId-1,2:tokenId-2}}
  mapping(address=>mapping(uint=>uint)) private _ownedTokens;

then in front-end, after setting up provider and contract, you just call this function:

    const myNfts = await contract!.getOwnedNfts();