---
title: 'Solidity WTF 103 31 單元'
lang: zh-tw
---

Solidity WTF 103 31 單元
===
:::info
:date: 2024/10/10
:::

[TOC]
# ERC20
## 簡介
`ERC20`以太坊上的標準，是V神參與的[EIP20](https://eips.ethereum.org/EIPS/eip-20)，實現了基本的代幣轉帳邏輯。
可以想像，`ERC20`就是實現`IERC20`的方法，`IERC20`則是給予一個規範，讓`ERC20`有一個標準去發行代幣。
## 使用方法

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.21;

import "./IERC20.sol";

contract ERC20 is IERC20 {
    mapping(address => uint256) public override balanceOf;
    mapping(address => mapping(address => uint256)) public override allowance;

    uint256 public override totalSupply;

    string public name;
    string public symbol;

    uint8 public decimals = 15;

    constructor(string memory name_, string memory symbol_){
        name = name_;
        symbol = symbol_;
    }

    function transfer(address recipient, uint amount) public override returns (bool) {
        balanceOf[msg.sender] -= amount;
        balanceOf[recipient] += amount;
        emit Transfer(msg.sender, recipient, amount);
        return true;
    }

    function approve(address spender, uint amount) public override returns (bool) {
        allowance[msg.sender][spender] = amount;
        emit Approval(msg.sender, spender, amount);
        return true;
    }

    function transferFrom(
        address sender,
        address recipient,
        uint amount
    ) public override returns (bool) {
        allowance[sender][msg.sender] -= amount;
        balanceOf[sender] -= amount;
        balanceOf[recipient] += amount;
        emit Transfer(sender, recipient, amount);
        return true;
    }

    function mint(uint amount) external {
        balanceOf[msg.sender] += amount;
        totalSupply += amount;
        emit Transfer(address(0), msg.sender, amount);
    }

    function burn(uint amount) external {
        balanceOf[msg.sender] -= amount;
        totalSupply -= amount;
        emit Transfer(msg.sender, address(0), amount);
    }
}

:::warning
注意`import`的`IERC20.sol`，可以去`Open Zeppelin`拿取。
:::
# IERC20
## 簡介
是`ERC20`的代幣標準接口合約，規定`ERC20`代幣需要實現的函數和事件。
所以`IERC20`不用管函數內部如何實現，只定義函數名稱、參數輸入、輸出參數。感覺像是分為內部和外部兩種，一個重點實現，另一個是接口。
## Open Zeppelin
這邊有`IERC20`的`sol`，`Open Zeppelin`有寫好一份。 [點選這](https://github.com/openzeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/IERC20.sol)