发红包的合约&银行合约

发红包的合约

案例分析：

pragma solidity ^0.6.1;

contract redpacket_demo{
    address payable public  tuhao;
    uint256 public rcount; // 红包数量，因为抢一个少一个，所以要记录
    uint public ave;
    mapping(address => bool) isStake;
    //1.fa hong bao
    constructor(uint256 count) public payable{
        require(msg.value > 0, "msg.value must >0");
        require(count > 0, "count must > 0");
        ave = msg.value/count;
        rcount = count;
        tuhao = msg.sender;
    }
    //2.qiang hong bao
    function stakeMoney() public payable {
        require(!isStake[msg.sender],"msg.sender must not stake");
        require(rcount > 0, "rcount must >0");
        require(getBalance() > 0, "getBalance() must > 0");
        uint256 randnum = uint256 (keccak256(abi.encode(msg.sender,tuhao,now,rcount)))%100;
        // msg.sender.transfer(randnum * getBalance()/ 100); //先乘后除，因为solidity不支持小数
        msg.sender.transfer(ave); //平均分配红包
        rcount --;
        isStake[msg.sender] = true;
    }
    //3.tuihui
    function kill() public payable{
        selfdestruct(tuhao);// 钱退回给土豪
    }
    function getBalance() public view returns(uint256){
        // 红包余额
        return address(this).balance;
    }
}

二、银行合约
包括存款，取款，转账，银行总账统计等业务。

pragma solidity ^0.6.1;

contract bank_demo{
    mapping(address => uint256) balances;// user's balance
    string public bankName;
    uint256 totalAmount; //总存款数
    constructor(string memory name) public {
        bankName = name;
        totalAmount = 0;
    }
    //存钱
    function deposit(uint256 amount) external payable{
        require(amount > 0, "amount must >0");
        require(msg.value == amount, "amount must equal msg.value");
        balances[msg.sender] += amount;
        totalAmount += amount;
        require(totalAmount == address(this).balance,"bank's balance is wrong"); // 统计的帐必须正确
    }

    //取钱
    function withdraw(uint256 amount) external payable{
        require(amount > 0, "amount must >0");
        require(balances[msg.sender]>=amount, "balance must enough!");
        msg.sender.transfer(amount);
        balances[msg.sender] -= amount;
        totalAmount -= amount;
        require(totalAmount == address(this).balance,"bank's balance is wrong");
    }

    // 转账给某人，transfer A->B(100), 
    // A=A-100; B = B+100;
    function transfer(address to, uint256 amount) external{
        require(amount > 0, "amount must > 0");
        require(balances[msg.sender] >= amount, "balance must enought!");
        balances[msg.sender] -= amount;
        balances[to] += amount;
        require(totalAmount == address(this).balance,"bank's balance is wrong");
    }

    function getBalance()external view returns(uint256){
        return balances[msg.sender];
    }

    function getTotalAmount() external view returns(uint256,uint256){
        return(totalAmount, address(this).balance);
    }
}