合同 "Coin" 应标记为摘要

Question

我想在 ERC-20 网络上创建一个令牌。

我想继承我合同中的接口。

当我继承表单界面时，它显示这个错误：

Contract "CpayCoin" should be marked as abstract.

solc truffle 版本：

  compilers: {
solc: {
  version: "0.8.10",    // Fetch exact version from solc-bin (default: truffle's version)
  docker: false,        // Use "0.5.1" you've installed locally with docker (default: false)
  settings: {          // See the solidity docs for advice about optimization and evmVersion
    optimizer: {
      enabled: false,
      runs: 200
    },
    evmVersion: "byzantium"
  }
}

},

有什么问题吗？我该如何解决这个问题？？？

这是我的界面:

    // SPDX-License-Identifier: MIT
pragma solidity >=0.4.22 <0.9.0;

interface IERC20 {
    function decimals() external view returns (uint8);

    function totalSupply() external view returns (uint256);

    function balanceOf(address account) external view returns (uint256);

    function transfer(address recipient, uint256 amount)
        external
        returns (bool);

    function allowance(address owner, address spender)
        external
        view
        returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function transferFrom(
        address sender,
        address recipient,
        uint256 amount
    ) external returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );
}

合同：

// SPDX-License-Identifier: MIT

pragma solidity >=0.4.22 <0.9.0;

import "./IERC-20.sol";

contract CpayCoin is IERC20 {
    //mapping
    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;

    //Unit256
    uint256 private _totalSupply;
    uint256 private _tokenPrice;

    // String
    string private _name;
    string private _symbol;

    //Address
    address _minter;

    constructor(
        string memory name_,
        string memory symbol_,
        uint256 totalSupply_
    ) {
        _minter = msg.sender;
        _balances[_minter] = _totalSupply;
        _tokenPrice = 10**15 wei;
        _name = name_;
        _symbol = symbol_;
        _totalSupply = totalSupply_;
    }

    // Modifier
    modifier onlyMinter() {
        require(msg.sender == _minter, "Only Minter can Mint!");
        _;
    }

    modifier enoughBalance(address adr, uint256 amount) {
        require(_balances[adr] >= amount, "Not enough Balance!");
        _;
    }

    modifier enoughValue(uint256 amount) {
        require(msg.value == amount * _tokenPrice, "Not enough Value!");
        _;
    }

    modifier checkZeroAddress(address adr) {
        require(adr != address(0), "ERC20: mint to the zero address");
        _;
    }

    // Functions
    function name() public view virtual returns (string memory) {
        return _name;
    }

    function symbol() public view virtual returns (string memory) {
        return _symbol;
    }

    function totalSupply() public view virtual override returns (uint256) {
        return _totalSupply;
    }

    function balanceOf(address adr)
        public
        view
        virtual
        override
        returns (uint256)
    {
        return _balances[adr];
    }

    function _mint(address account, uint256 amount)
        internal
        virtual
        onlyMinter
        checkZeroAddress(account)
    {
        _totalSupply += amount;
        _balances[account] += amount;

        emit Transfer(address(0), account, amount);
    }

    function _burn(address account, uint256 amount)
        internal
        virtual
        onlyMinter
        checkZeroAddress(account)
    {
        uint256 accountBalance = _balances[account];
        unchecked {
            _balances[account] = accountBalance - amount;
        }

        _totalSupply += amount;
        emit Transfer(account, address(0), amount);
    }

    function _transfer(
        address sender,
        address recipient,
        uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        uint256 senderBalance = _balances[sender];
        require(
            senderBalance >= amount,
            "ERC20: transfer amount exceeds balance"
        );

        unchecked {
            _balances[sender] = senderBalance - amount;
        }

        _balances[recipient] += amount;

        emit Transfer(sender, recipient, amount);
    }

    function _approve(
        address owner,
        address spender,
        uint256 amount
    ) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }
}

Answer 1

Solidity 目前 (v0.8) 无法判断 class（合约）实现了接口。相反，is 关键字用于标记继承，如“派生自”。

因此 CpayCoin is IERC20 表达式将 CpayCoin 标记为子项，将 IERC20 标记为父项 - 而不是接口。

IERC20（父级）定义了 CpayCoin（子级）未实现的几个函数（例如 decimals() 和 transfer()），这使得 CpayCoin 摘要 class.

解法：

在CpayCoin中实现IERC20接口中定义的所有函数，使其不抽象class，并使其遵循ERC-20标准。然后您可以自由删除继承，因为它变得多余。

或者只是删除继承以没有任何未实现的函数定义（但这样合约将不遵循 ERC-20 标准）。

请注意，在您当前的代码中，_transfer() 内部函数无法访问。我建议实现一个调用此内部 _transfer().

的 transfer() 外部函数

Answer 2

正如 Petr Hejda 在之前的回答中所述：您需要实现所有声明的函数才能拥有普通合约而不是抽象合约。

对于在 truffle 或 hardhat 等本地环境中获取 Contract <ContractName> should be mark as abstract 时遇到此问题的人，您可以使用在线编译器 Remix 找出缺少实现的功能。尝试编译合约后 Remix 中的错误消息明确告诉您缺少的函数。

合同 "Coin" 应标记为摘要

Contract "Coin" should be marked as abstract

solidity

smartcontracts