ERC20代币合约 / 学习智能合约#5

ERC20代币想必大家不陌生了，在以太坊上有数以千计的ERC20代币！本着学以致用的目的，自己也发个币装一把。

先上代码：

pragma solidity >=0.4.22 <0.7.0;

 abstract contract ERC20Interface {
  string public name;
  string public symbol;
  uint8 public  decimals;
  uint public totalSupply;


  function transfer(address _to, uint256 _value) public virtual returns (bool success);
  function transferFrom(address _from, address _to, uint256 _value) public virtual returns (bool success);
  
  function approve(address _spender, uint256 _value) public virtual returns (bool success);
  function allowance(address _owner, address _spender) public virtual view returns (uint256 remaining);

  event Transfer(address indexed _from, address indexed _to, uint256 _value);
  event Approval(address indexed _owner, address indexed _spender, uint256 _value);

}


contract ERC20 is ERC20Interface {
    mapping(address => uint256) public balanceOf;
    mapping(address => mapping(address => uint256)) allowed;
    
    constructor() public {
       name = "Lemool"; 
       symbol = "LEM";
       decimals = 0;
       totalSupply = 10000000;
       balanceOf[msg.sender] = totalSupply;
    }
    
    
  function transfer(address _to, uint256 _value) public override returns (bool success) {
      require(_to != address(0));
      require(balanceOf[msg.sender] >= _value);
      require(balanceOf[ _to] + _value >= balanceOf[ _to]);
      
      
      balanceOf[msg.sender] -= _value;
      balanceOf[_to] += _value;
      
      emit Transfer(msg.sender, _to, _value);
      
      return true;
  }
  
  
  function transferFrom(address _from, address _to, uint256 _value) public override returns (bool success) {
      require(_to != address(0));
      require(allowed[_from][msg.sender] >= _value);
      require(balanceOf[_from] >= _value);
      require(balanceOf[ _to] + _value >= balanceOf[ _to]);
      
      balanceOf[_from] -= _value;
      balanceOf[_to] += _value;
      
      allowed[_from][msg.sender] -= _value;
      
      emit Transfer(msg.sender, _to, _value);
      return true;
  }
  
  function approve(address _spender, uint256 _value) public override returns (bool success) {
      allowed[msg.sender][_spender] = _value;
      
      emit Approval(msg.sender, _spender, _value);
      return true;
  }
  
  function allowance(address _owner, address _spender) public override view returns (uint256 remaining) {
      return allowed[_owner][_spender];
  }

}

ERC20是有标准接口的，其实都很简单，就是几个参数和几个转帐的方法！想当年很多项目就是靠着这几行代码卷钱无数，现在想来会不会有点后悔呢。

在上面转帐的方法还是自己实现了一下，其实还有一种更简单和安全的方法：OpenZeppelin。只有少数几行代码就可以实现ERC20代币合约！

用前先安装一下：npm install @openzeppelin/contracts

pragma solidity >=0.4.22 <0.7.0;

import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/token/ERC20/ERC20Detailed.sol";

contract TutorialToken is ERC20, ERC20Detailed {
    constructor() ERC20Detailed("Lemool", "LEM", 0) public {
        _mint(msg.sender, 10000000);
    }
}

短短五六行代码就全搞定了，想想是不是很牛啊！感兴趣的朋友可以一试！