Openzeppelin库第十一期：再叙ERC20发币

1. 编写ERC20合约
2. 通过remix进行部署
3. 连接到MetaMask上面
4. 通过myetherwallet.com进行转账测试等操作

• 新建1-ERC20文件夹，打开终端，truffle init ，

pragma solidity ^0.4.0;
library SafeMath {

    /**
    * @dev Multiplies two numbers, throws on overflow.
    */
    function mul(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
        // Gas optimization: this is cheaper than asserting 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
        if (_a == 0) {
            return 0;
        }

        c = _a * _b;
        assert(c / _a == _b);
        return c;
    }

    /**
    * @dev Integer division of two numbers, truncating the quotient.
    */
    function div(uint256 _a, uint256 _b) internal pure returns (uint256) {
        // assert(_b > 0); // Solidity automatically throws when dividing by 0
        // uint256 c = _a / _b;
        // assert(_a == _b * c + _a % _b); // There is no case in which this doesn't hold
        return _a / _b;
    }

    /**
    * @dev Subtracts two numbers, throws on overflow (i.e. if subtrahend is greater than minuend).
    */
    function sub(uint256 _a, uint256 _b) internal pure returns (uint256) {
        assert(_b <= _a);
        return _a - _b;
    }

    /**
    * @dev Adds two numbers, throws on overflow.
    */
    function add(uint256 _a, uint256 _b) internal pure returns (uint256 c) {
        c = _a + _b;
        assert(c >= _a);
        return c;
    }
}

contract ERC20  {
    //uint public totalSupply; //总量
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(
        address indexed owner,
        address indexed spender,
        uint256 value
    );

    function allowance(address _owner, address _spender) public view returns (uint256);
    function totalSupply() public view returns (uint256);
    function balanceOf(address _who) public view returns (uint256);
    function transfer(address _to, uint256 _value) public returns (bool);



    function transferFrom(address _from, address _to, uint256 _value) public returns (bool);

    function approve(address _spender, uint256 _value) public returns (bool);

}

contract childERC20 is ERC20 {
    //基本的三个成员
    string public name; //自动创建访问器
    string public symbol; //代号
    uint8 public decimals; //精度
    using SafeMath for uint256;
    uint256 internal totalSupply_;

    //余额
    mapping(address => uint) balances;

    //配额/量值
    mapping(address => mapping(address => uint)) allowances;

    //构造函数 第四个参数是发行量
    function childERC20 (string _name, string _symbol, uint8 _decimals, uint _initialSupply) {
        name = _name;
        symbol = _symbol;
        decimals = _decimals;
        totalSupply_ = _initialSupply * 10 ** uint8(decimals);
    }

    function balanceOf(address who) public view returns(uint 256) {
        return balances[who];
    }

    function totalSupply() public view returns (uint 256) {
        return totalSupply_;
    }

    function transfer(address _to, uint256 _value) public returns (bool) {
        require(_value <= balances[msg.sender]);
        require(_to != address(0));

        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        emit Transfer(msg.sender, _to, _value);
        return true;
    }

    function transferFrom(
        address _from,
        address _to,
        uint256 _value
    )
    public
    returns (bool)
    {
        require(_value <= balances[_from]);
        require(_value <= allowed[_from][msg.sender]);
        require(_to != address(0));

        balances[_from] = balances[_from].sub(_value);
        balances[_to] = balances[_to].add(_value);
        allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
        emit Transfer(_from, _to, _value);
        return true;
    }


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


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

}

• 打开metamask和remix并部署

• 要对代币进行操作：