solidity合约标准----ERC

两个概念

1. ERC
2. EIP

常见的ERC标准

1. ERC-20Token Standard（早期区块链项目都基于此标准）
2. ERC-721 Non-Fungible Token Standard(非同质化标准)
3. ERC-165 Standard Interface Detection
4. ERC-777 Token Standard
   其它标准见 eips.ethereum.org/etc

ERC-20标准详解

ERC-20为一套接口，实现了这套接口，即为实现这套标准

pragma solidity^0.6.1;
  interface IERC20 {
  function totalSupply() external view returns (uint256);

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

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

  function transfer(address to, uint256 value) external returns (bool);

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

  function transferFrom(address from, address to, uint256 value)
    external returns (bool);

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

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

pragma solidity^0.6.1;
import "./IERC20.sol";
contract test_erc20 is IERC20{

  string private _name; //指定名称
  uint256 private _totalSupply;//存储总的发行量
  address private admin;//定义管理员，用于发布发行量，由于ERC20标准没有规定如何发行，因此需要自己设置发行机制
  mapping(address=>uint256) private _balances;
  mapping(address=>mapping(address=>uint256))private _allowance;

  constructor(string memory name) public{
      _name=name;
     _totalSupply=0;
     admin=msg.sender;
  }
  function name() external view returns(string memory){
      return _name;
  }
  //挖矿函数
  function mint(address to ,uint256 value) external{
      require(admin==msg.sender,"only admin can do");
      require(address(0)!=to,"to must is an address");
      _balances[to]+=value;
      _totalSupply+=value;
      emit Transfer(address(0),to,value);

  }
  //总的发行量
  function totalSupply() external override view returns (uint256){
      return _totalSupply;
  }
  
  //账户的余额
  function balanceOf(address who) external override view returns (uint256){
      return _balances[who];
  }
 //查看授权的余额
  function allowance(address owner, address spender) override
    external view returns (uint256){
         return _allowance[owner][spender];
    }
//转账接口  A-->B 200   A-200   B+200   
  function transfer(address to, uint256 value) override external returns (bool){
        require(value>0,"value must >0");
        require(_balances[msg.sender]>=value,"balance must enough!");
        require(address(0)!=to,"to must is an address");
        _balances[msg.sender]-=value;
        _balances[to]+=value;   
        //调用事件函数
        emit Transfer(msg.sender,to,value);  
  }
//授权  
  function approve(address spender, uint256 value)override 
    external returns (bool){
        require(_balances[msg.sender]>=value,"balance must enough!");
        require(address(0)!=spender,"to must is an address");
        _allowance[msg.sender][spender]=value;
        //调用事件
        emit Approval(msg.sender,spender,value);

    }
 //授权转账
  function transferFrom(address from, address to, uint256 value)override
    external returns (bool){
        require(address(0)!=to,"to must is an address");
        require(value>0,"value must >0");
        require(_allowance[from][to]>=value,"allowance's value must enough");
        _allowance[from][to]-=value;
        _balances[from]-=value;
        _balances[to]+=value;
        //调用事件
        emit Transfer(from,to,value);

    }
}

函数测试

选择第一个账户为管理员，负责部署合约

1. 部署合约

2. 模拟挖矿，赋予参与方金额

注意：只有管理员拥有挖矿权限，即调用挖矿函数

3.查询余额以及总的发行量

这里是引用

4.进行转账

第三账户—>第二个账户
转账的三要素：谁转账，转给谁，转多少

5.进行授权

授权第三方进行转账

6.授权转账

注意：这一步是在上一步骤的基础上进行的，转账的三要素要匹配，否则会出现错误