ERC2981 NFT Royalties Implementation in a ERC721 Marketplace

Question

I've read already many posts regarding this topic, but I just can't wrap my head around this Royalty implementation thing. Pls help me out, I don't know how I should play with this thing. what is feeNumerator? _setDefaultRoyalty(address receiver, uint96 feeNumerator) is it NFT Price? Nft Royalty Percent? Pls take a look at the following contract and help me with how I can implement NftRoyalty in this contract. Am I doing it right? if not then pls correct me. Thanks.

// SPDX-License-Identifier: MIT
pragma solidity 0.8.8;

import "hardhat/console.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Counters.sol";
import "@openzeppelin/contracts/token/common/ERC2981.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";

contract PodShip is ERC721URIStorage, ERC2981, Ownable {
    using Counters for Counters.Counter;
    Counters.Counter private _podcastId;
    Counters.Counter private _nftId;

    struct Podcast {
        address nftCreator;
        address nftOwner;
        string nftName;
        string nftDescription;
        uint256 nftPrice;
        uint256 nftRoyaltyPercent;
        uint256 nftId;
        bool listed;
    }


    mapping(uint256 => Podcast) podcastId;

    constructor() ERC721("PodShip NFTs", "PODSHIP") {}

    function mintNft(
        string memory ipfsURI,
        string memory _nftName, 
        string memory _nftDescription, 
        uint256 _nftPrice, 
        uint256 _nftRoyaltyPercent) public returns(uint256) {
            require(_nftPrice > 0, "NFT Price not set correctly");
            require(_nftRoyaltyPercent > 0 && _nftRoyaltyPercent <= 50, "NFT Royalty should be in-between 1 & 50");

            _podcastId.increment();
            _nftId.increment();
            uint256 nft_Id = _nftId.current();

            _safeMint(msg.sender, nft_Id);
            _setTokenURI(nft_Id, ipfsURI);

            podcastId[_podcastId.current()] = Podcast(
            payable(msg.sender), 
            payable(msg.sender), 
            _nftName, 
            _nftDescription, 
            _nftPrice, 
            _nftRoyaltyPercent,
            nft_Id,
            false
        );
        console.log(nft_Id);
        console.log(_podcastId.current());

        return nft_Id;
    }

    function listNFT(uint256 _podcastID) public {
        require(msg.sender == podcastId[_podcastID].nftOwner && msg.sender == podcastId[_podcastID].nftCreator, "Only Owner can list his NFT");
        podcastId[_podcastID].listed = true;
        approve(address(this), podcastId[_podcastID].nftId);
        setApprovalForAll(address(this), true);
        _setDefaultRoyalty(podcastId[_podcastID].nftCreator, uint96(podcastId[_podcastID].nftRoyaltyPercent));
    }

Answer 1

All info can be found here: https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/common/ERC2981.sol#L9-L23

Basically the royalty fee is calculated as a fraction of the sale price. The fraction is calculated as feeNumerator/10000. So if the price is 1 ETH and feeNumerator = 500, the royalty is 0.05 ETH.

_setDefaultRoyalty(address receiver, uint96 feeNumerator) sets the royalty for all NFTs in the collection.

In your code, I believe you want to set different royalties for different token ids. In this case you should use:

_setTokenRoyalty(podcastId[_podcastID].nftId, podcastId[_podcastID].nftCreator, uint96(podcastId[_podcastID].nftRoyaltyPercent));