使用 uint256 的字符串不适用于 ERC721EnumerableUpgradeable

Question

就像标题说我无法使用字符串进行编译一样，我不断收到找不到标识符的信息。 这是我的 .sol 合约的开始

import "@openzeppelin/contracts-upgradeable/token/ERC721/extensions/ERC721EnumerableUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
import "@openzeppelin/contracts-upgradeable/utils/StringsUpgradeable.sol";

contract NFT is Initializable, StringsUpgradeable, ERC721EnumerableUpgradeable, OwnableUpgradeable {
using Strings for uint256; 

请帮忙！

谢谢！

Answer 1

导入的

StringsUpgradeable.sol

文件包含一个名为

StringsUpgradeable

的库 - 而不是

Strings

。

此外，由于它是一个库，因此无法继承它，因此您需要将其从

NFT

父级列表中删除。

pragma solidity ^0.8;

import "@openzeppelin/contracts-upgradeable/token/ERC721/extensions/ERC721EnumerableUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/access/OwnableUpgradeable.sol";
import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
import "@openzeppelin/contracts-upgradeable/utils/StringsUpgradeable.sol";

// removed `StringsUpgradable` from the parents list
contract NFT is Initializable, ERC721EnumerableUpgradeable, OwnableUpgradeable {

    // replaced `Strings` to `StringsUpgradable`
    using StringsUpgradeable for uint256; 
}

Answer 2

我想编译合同，它给了我这个错误。感谢您的帮助 以前的版本编译没有错误，现在就不行了？