NFT市场是如何运作的？

Question

如果我想实现一个小的NFT市场，并希望用户能够将项目出售，而其他用户购买这些，我应该怎么做呢？我是否需要在每次有人提出要出售的东西时，签订一份得到批准的市场合同?当有人购买该商品时，合同将执行safeTransferFrom函数吗？

Answer 1

是的，这是人们通常做的一种方式。

如果您的市场只适用于一个特定的令牌，则可以使用更好的选项。

Answer 2

我用这个合同：

// SPDX-License-Identifier: MIT
pragma solidity >=0.4.21 <0.9.0;

import '@openzeppelin-contracts/contracts/token/ERC721/ERC721.sol';
import '@openzeppelin-contracts/contracts/finance/PaymentSplitter.sol';

contract BALANCE is ERC721 {
    event NftBought(address _seller, address _buyer, uint256 _price);

    mapping (uint256 => uint256) public tokenIdToPrice;
    uint public nextTokenId;
      address public admin;

    constructor() ERC721('Balance', 'BALANCE') {
          admin = msg.sender;
    }
    
      function mint(address to) external {
    require(msg.sender == admin, 'only admin');
    if(nextTokenId < 2){_safeMint(to, nextTokenId);
    nextTokenId++;
    }
  } 
    
              function _baseURI() internal view override returns (string memory) {
    return 'https://.herokuapp.com/';
  }

    function allowBuy(uint256 _tokenId, uint256 _price) external {
        require(msg.sender == ownerOf(_tokenId), 'Not owner of this token');
        require(_price > 0, 'Price zero');
        tokenIdToPrice[_tokenId] = _price;
    }

    function disallowBuy(uint256 _tokenId) external {
        require(msg.sender == ownerOf(_tokenId), 'Not owner of this token');
        tokenIdToPrice[_tokenId] = 0;
    }
    
    function buy(uint256 _tokenId) external payable {
        uint256 price = tokenIdToPrice[_tokenId];
        require(price > 0, 'This token is not for sale');
        require(msg.value == price, 'Incorrect value');
        
        address seller = ownerOf(_tokenId);
        _transfer(seller, msg.sender, _tokenId);
        tokenIdToPrice[_tokenId] = 0; // not for sale anymore
        payable(seller).transfer(msg.value); // send the ETH to the seller

        emit NftBought(seller, msg.sender, msg.value);
    }
}

我叫allowBuy('tokenId'，'prince_in_WEI')来设置id价格，然后发送buy('tokenId')，尽管我对它有很大的异议。