入门小白简单快速地学会编写erc20（有标准的）

提供编写erc20的基本思路

思路

题目：发布一个erc20token，设置部署合约的地址为管理员，管理员可以增发token，但初始总量为2000万个，用户可以销毁自己的token

编写一个合约功能前我们要知道需要的参数

  1. 币叫什么

  2. 最小单位是多少

  3. 币量初始值是多少

  4. 之后呢，这些币应该是谁的，创始人的吧，那就要使用mapping捆绑其地址‘

    但是后面铸造也不一定全是给创始人的

  5. 同时我们还需要实现授权功能，也就是创始人给的token赋权给一些人吧，那么当这些人使用这些授权的token的时候，授权资产减少，那么创始人的token也减少，那么需要写双重映射了

  6. 准备工作做好了，正片开始，首先肯定是要初始化的，咱们使用构造函数自动初始化

  7. 那么我们需要知道，什么时候token转了，授权了，铸造了，毁了，需要创建事件，emit触发事件，事件里面要使用indexed关键字

  8. 接着就是完善函数功能了吧

开始写

  1. 第一步声明我们要写的变量
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
constract token{
string public token_name="beaventao"//币全名
string public token_symbol="bea"//币简称
uint8 public dot=18;
uint256 public total_token=20000000*(10**uint256(dot))//这里是最小单位
address public owner;
}

  1. 捆绑部分

    mapping(address => uint256) public balances;
mapping(address => mapping(address => uint256)) public allowances;

  2. 初始化

    constructor() {
       owner = msg.sender;
       balances[owner] = total_token;
   }

  3. 创造事件

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

  4. 转账函数

    function transfer(address _to, uint256 _value) public returns (bool) {
       require(balances[msg.sender] >= _value, "Not enough tokens");
       balances[msg.sender] -= _value;
       balances[_to] += _value;
       emit Transfer(msg.sender, _to, _value);
       return true;
   }

  5. 授权函数

    function approve(address _spender, uint256 _value) public returns (bool) {
       allowances[msg.sender][_spender] = _value;
       emit Approval(msg.sender, _spender, _value);
       return true;
   }

    这里解释两点

    1. 这里使用 “=“ 而不是 ”+=” 因为是授权，必须是精确的数值
    2. [msg.sender] [_spender] 上面双重映射的另一个形式。

  6. 授权转账函数

     function transferFrom(address _from, address _to, uint256 _value) public returns (bool) {
       require(balances[_from] >= _value, "Not enough tokens");
       require(allowances[_from][msg.sender] >= _value, "Allowance exceeded");

       balances[_from] -= _value;
       balances[_to] += _value;
       allowances[_from][msg.sender] -= _value;
       emit Transfer(_from, _to, _value);
       return true;
   }

  7. 铸造和销毁函数

    function mint(address _to, uint256 _value) public returns (bool) {
       require(msg.sender == owner, "Only the owner can mint tokens");
       total_token += _value;
       balances[_to] += _value;
       emit Mint(_to, _value);
       emit Transfer(address(0), _to, _value);
       return true;
   }

   function burn(address _from, uint256 _value) public returns (bool) {
       require(msg.sender == owner, "Only the owner can burn tokens");
       require(balances[_from] >= _value, "Not enough tokens to burn");
       total_token -= _value;
       balances[_from] -= _value;
       emit Burn(_from, _value);
       emit Transfer(_from, address(0), _value);
       return true;
   }
}

    针对address(0)解释

    1. address(0) 表示以太坊地址空间中的一个特定地址，这个地址通常被用来表示“空地址”或“无效地址”。它有助于明确地表示某个操作或状态没有实际关联的地址。
    2. 我理解为源泉地址，如同无尽的水源，我们只是从里面抽了一些水，销毁也就是把水送回去。这个过程只要没到其他人的手里，就不会被滥用，也就是无关系地址
    3. emit的参数数量要与事件对应

代码识别

下面是个错误代码，通过上面学习你把它改成正确的就算搞懂了

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
contract token{
 string public token_name="beaventao";
 string public token_symbol="bea";
 uint8  public dot=18;
 uint256 public total_token=20000000*(10**dot);
 address public owner;

mapping (address =>uint256) public balances;
mapping (address=> mapping (address=>uint256)) allowances;

constructor(){
 owner=msg.sender;
 balances[owner]=total_token;
}

 event transfer(address indexed from,address indexed to,uint256 value);
 event approval(address indexed from,address indexed to,uint256 value);
 event mint(address indexed from,address indexed to,uint256 value);
 event burn(address indexed from,address indexed to,uint256 value);

function transfer(address _to,uint256 _value) public returns(bool){
    require(balances[owner]>=_value,"not enough token");
    balances[owner]-=_value;
    balances[_to]+=_value;
    emit transfer(msg.sender, _to,_value);
    return true;
}

function approval(address _spendright, address _to,uint256 _value) public returns(bool){
    require(balances[msg.sender]>=_value,"error");
    allowances[msg.sender][_spendright]+=value;
    emit approval(msg.sender, _spendright,_value);
    return true;
}

function transferes(address _from,address _to,uint256 _value) returns (bool){
    require(allowances[msg.sender][_spendright]>=_value,"not enough money");
    balances[_to]+=_value;
    balances[msg.sender]-=_value;
    allowances[msg.sender][_spendright]-=_value;
    emit transfer(_from, _to, _value);
    return true;
}

function mint(address _to,uint256 token_num) public returns (bool){
    require(msg.sender,"you don't have right");
    total_token+=token_num;
    balances[_to]+=token_num;
    emit mint(_to, token_num);
    emit transfer( _to, token_num);
    return true;
}

function burn(address _to,uint256 token_num) public returns (bool){
    require(msg.sender,"you don't have right");
    total_token-=token_num;
    balances[_to]-=token_num;
    emit burn(_to, token_num);
    return true;
}
}

标准的erc20

其改变最主要的是对address(0)的检验，以及保持授权金额的同步，保证准确

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract BaseERC20 {
    string public name = "BaseERC20";
    string public symbol = "BERC20";
    uint8 public decimals = 18;
    uint256 public totalSupply = 100000000 * (10 ** uint256(decimals));
    address public owner;

    mapping(address => uint256) balances;
    mapping(address => mapping(address => uint256)) allowances;

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

    constructor() {
        owner = msg.sender;
        balances[msg.sender] = totalSupply;
    }

    function balanceOf(address _owner) public view returns (uint256 balance) {
        return balances[_owner];
    }

    function transfer(address _to, uint256 _value) public returns (bool success) {
        require(_to != address(0), "Invalid address");
        require(balances[msg.sender] >= _value, "ERC20: transfer amount exceeds balance");

        balances[msg.sender] -= _value;
        balances[_to] += _value;

        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_from != address(0) && _to != address(0), "Invalid address");
        require(balances[_from] >= _value, "ERC20: transfer amount exceeds balance");
        require(allowances[_from][msg.sender] >= _value, "ERC20: transfer amount exceeds allowance");

        balances[_from] -= _value;
        balances[_to] += _value;
        allowances[_from][msg.sender] -= _value;

        emit Transfer(_from, _to, _value);
        return true;
    }

    function approve(address _spender, uint256 _value) public returns (bool success) {
        require(_spender != address(0), "Invalid address");

        allowances[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }

    function allowance(address _owner, address _spender) public view returns (uint256 remaining) {
        return allowances[_owner][_spender];
    }
}
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