Smart Contract NFT how to add price by code to whole items in collection?

Question

Greeting,

Could you tell me how to add price for every item in collection hosted by OpenSea?

So, I have working code, It created:

1.Collection name (from construct before deploy)

2.NFT symbol (from construct before deploy)

3.URI to ipfs (from construct before deploy ex: ipfs://QmQtP8RNjvcVtKqcPwukgckWF74ojBjzahVzE3qCCnqv4f/

My smart contract example:

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;

import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

import "@openzeppelin/contracts/utils/Context.sol";
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/utils/math/SafeMath.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";

contract NFT is ERC721Enumerable, Ownable {
  using Strings for uint256;

  string public baseURI;
  string public baseExtension = ".json";
  uint256 public cost = 10000000000000000;
  uint256 public maxSupply = 10000;
  uint256 public maxMintAmount = 100;
  bool public paused = false;
  mapping(address => bool) public whitelisted;

  constructor(
    string memory _name,
    string memory _symbol,
    string memory _initBaseURI
  ) ERC721(_name, _symbol) {
    setBaseURI(_initBaseURI);
    mint(msg.sender, 5); // 5- for test
  }

  // internal
  function _baseURI() internal view virtual override returns (string memory) {
    return baseURI;
  }

  // public
  function mint(address _to, uint256 _mintAmount) public payable {
    uint256 supply = totalSupply();
    require(!paused);
    require(_mintAmount > 0);
    require(_mintAmount <= maxMintAmount);
    require(supply + _mintAmount <= maxSupply);

    if (msg.sender != owner()) {
        if(whitelisted[msg.sender] != true) {
          require(msg.value >= cost * _mintAmount);
        }
    }

    for (uint256 i = 1; i <= _mintAmount; i++) {
      _safeMint(_to, supply + i);
    }
  }

  function walletOfOwner(address _owner)
    public
    view
    returns (uint256[] memory)
  {
    uint256 ownerTokenCount = balanceOf(_owner);
    uint256[] memory tokenIds = new uint256[](ownerTokenCount);
    for (uint256 i; i < ownerTokenCount; i++) {
      tokenIds[i] = tokenOfOwnerByIndex(_owner, i);
    }
    return tokenIds;
  }

  function tokenURI(uint256 tokenId)
    public
    view
    virtual
    override
    returns (string memory)
  {
    require(
      _exists(tokenId),
      "ERC721Metadata: URI query for nonexistent token"
    );

    string memory currentBaseURI = _baseURI();
    return bytes(currentBaseURI).length > 0
        ? string(abi.encodePacked(currentBaseURI, tokenId.toString(), baseExtension))
        : "";
  }

  //only owner
  function setCost(uint256 _newCost) public onlyOwner {
    cost = _newCost;
  }

  function getCost() public view returns (uint256) {
    return cost;
  }

  function setmaxMintAmount(uint256 _newmaxMintAmount) public onlyOwner {
    maxMintAmount = _newmaxMintAmount;
  }

  function setBaseURI(string memory _newBaseURI) public onlyOwner {
    baseURI = _newBaseURI;
  }

  function setBaseExtension(string memory _newBaseExtension) public onlyOwner {
    baseExtension = _newBaseExtension;
  }

  function pause(bool _state) public onlyOwner {
    paused = _state;
  }
 
 function whitelistUser(address _user) public onlyOwner {
    whitelisted[_user] = true;
  }
 
  function removeWhitelistUser(address _user) public onlyOwner {
    whitelisted[_user] = false;
  }

  function withdraw() public onlyOwner {
      uint256 balance = address(this).balance;
      payable(msg.sender).transfer(balance);
  }
}

and my item json file example:

{
  "description": "Test Description",
  "external_url": "http://testurl.com",
  "image": "ipfs://QmSrkLg3UR5AUthhCZfrK9nrX3fxJJ4aCJK7B99rUkCa72/4.png",
  "name": "Test Name #4",
  "symbol": "TNFT",
  "collection": {
    "name": "TestNFT123_321",
    "family": ""
  },
  "date": 1643919095,
  "attributes": {
    "Story": "In Caffe",
    "Company": "Test Company",
    "Some": "thing else"
  }
}

On the OpenSea I have created collection name with items, but, with active price button. What I made wrong?

Thanks for help.

Answer 1

I investigated this issue, so:

1. Listing items on OpenSea could be with API endpoints (see OpenSea docs, and here ).
2. OpenSea listing could be on mai.net or Rinkeby.network only (as of today no Polygon, BSC...)
3. There are a lot of clickers, which emulate add item, name, price on Polygon.network.

Waiting for API V2 OpenSea =((