一个水龙头合约

新建Faucel.sol

// SPDX-License-Identifier: SimPL-2.0
pragma solidity >=0.7.0 <0.9.0;
interface DaiToken {
  function transfer(address dst, uint wad) external returns(bool);
  function balanceOf(address guy) external view returns (uint);
}
// 定义一个合约
contract Faucel {
  DaiToken daitoken;
  constructor(){
    daitoken = DaiToken(0xf1DE2d4c9DA3201B82402b4c3cD06E7E128A1430);
  }
  uint unlock_time;
  function withdraw(uint256 amount) public {
    require(unlock_time<block.timestamp, "Account is locked!");
    require(amount <= 10000000000000000000);
    // 指定调用者的地址  单位 wei
    daitoken.transfer(msg.sender, amount);
    // msg.sender.transfer(amount);
    unlock_time = block.timestamp+2629743;//  default project funding period = 1 month
  }
  // 有且只有一个没有函数名的函数  回退函数
  // payable 可支付的
  fallback () payable external {}
  receive () payable external {}
}

// pragma solidity ^0.4.0;
contract Contract1 {
  constructor() public payable{}
  function send5VdtToReceiver(address payable _receiver) payable public{
    _receiver.transfer(5);
  }
}
constract Contract2 {
  address public payContract;
  constructor(address _add) payable public {
    payContract = _add;
  }
  function triggerContract1(address _receiver) payable public {
    payContract.call(abi.encodeWithSignature("send5VdtToReceiver(address)", _receiver));
    require(1==2);
  }
}
contract Contract3 {
  address  public payContract;
  constructor(address _add) payable public  {
    payContract = _add;
  }
  function triggerContract2(address _receiver) payable public {
    payContract.call(abi.encodeWithSignature("triggerContract1(address)", _receiver));
  }
}

tips:

• 当刚创建合约的时候，过一会在转账，因为可能转账失败