//SPDX-License-Identifier:MTT
pragma solidity ^0.8.24;interface erc20{function name()external view returns (string memory);//查看代币的名称function symbol() external view returns(string memory);//查看代币简称function totalSupply()external view returns(uint);//查看代币的总供应量function decimal()external view returns(uint8);//查看代币的精度function balanceOf(address account)external view returns(uint);//查看某账户的余额function transfer(address recipient ,uint amount) external payable returns(bool);//合约的调用者向某地址发送代币function approve(address spender ,uint amount) external returns(bool);//合约调用者向某一地址指定代币数量function allowance(address owner,address spender) external view returns(uint);//查看转账授权的金额function transferDirect(address _form,address _to,uint amount) external returns(bool);//直接执行转账操作function transferByApproves(address _to,uint amount) external returns(bool);//通过approve执行转账操作
}contract erc20tokens{//定义需要的状态变量string public _name;string public _symbol;uint public _totalSupply;uint8 public _decimal;mapping(address=>uint)public balances;mapping(address=>mapping(address=>uint)) public approves;constructor(//给状态变量进行赋值操作，在构造函数里面赋值时候仅仅会进行一次string memory _name_,string memory _symbol_,uint _totalSupply_,uint8 _decimal_) {_name=_name_;_symbol=_symbol_;_totalSupply =_totalSupply_;_decimal=_decimal_;}event Transfer(address _from,address _to,uint amount);//定义事件，记录转账操作event Approves(address _from,address _to,uint amount);//定义事件，记录授权操作，以及授权的余额//实现interface接口的函数function name()external view returns (string memory)//查看代币的名称{return _name;}function symbol() external view returns(string memory)//查看代币简称{return _symbol;}function totalSupply()external view returns(uint)//查看代币的总供应量{return _totalSupply;}function decimal()external view returns(uint8)//查看代币的精度{return _decimal;}function balanceOf(address account)external view returns(uint)//查看某账户的余额{return balances[account];}function transfer(address recipient ,uint amount) external returns(bool)//合约的调用者向某地址发送代币{require (balances[msg.sender]<=amount,"Sorry,you have no enough amount to send");return _transfer(msg.sender,recipient,amount);}function approve(address spender ,uint amount) external returns(bool)//合约调用者向某一地址授权指定数量代币{require(approves[msg.sender][spender]==0,"reapproved");approves[msg.sender][spender]=amount;return true;}function allowance(address owner,address spender) external view returns(uint)//查看转账授权的金额{return approves[owner][spender];}function transferByApproves(address _to,uint amount) internal returns(bool){address _from=msg.sender;require(approves[_from][_to]>=amount,"You hava no right to send too much");emit Approves(_from,_to,amount);approves[_from][_to]-=amount;return _transfer(_from,_to,amount);}function transferDirect(address _from,address _to,uint amount) external returns(bool)//执行转账操作{require(balances[_from]>=amount,"You have no enough monay");return _transfer(_from,_to,amount);}function _transfer(address _from,address _to,uint amount) internal returns (bool)//转账操作集成于_transfer函数，通过其他需要用到转账的函数只需要通过调用_transfer函数就可以{require(balances[_from]>=amount,"Sorry, the amount is too low");//只要调用_transfer 函数就会触发事件balances[_from]-=amount;balances[_to]+=amount;emit Transfer(_from,_to,amount);return true;}
}
ps:
授权转账的主要用途包括：
-
代理转账：允许另一个地址代表你进行转账操作，这在复杂的合约交互中特别有用。例如，允许某个合约在你的代币余额中进行交易，而无需事先将代币转移到合约地址。
-
限制额度：通过
approve函数授权一个特定的地址可以转移的代币数量，可以帮助减少合约中的风险，因为授权的数量通常是有限的。 -
灵活性：授权机制允许你动态地管理你的资金，可以随时修改授权的地址和数量，这为复杂的合约逻辑提供了更大的灵活性和安全性。