virtual

标记此函数可以被重写。只有标记为virtual的函数才可以重写(override)

pragma solidity >= 0.4.0 <0.9;
import "hardhat/console.sol";

contract IVirtual {
    function fun() public virtual m{
        console.log("virtual fun");
    }

    modifier m() virtual{
        console.log("virtual m()");
        _;
    }
}

contract Virtual is IVirtual{
    constructor(){
        super.fun();//这里的modifier实际会调用子类的m()
    }

    modifier m() override{
        console.log("local m()");
        _;
    }
    function fun() public override m{ //重载需要加override,并且权限得保持一致,不能上面public,下面external
        console.log("local fun");
    }
}

contract IVirtual2 {
    function fun() public virtual m{
        console.log("virtual2 fun");
    }

    modifier m() virtual{
        console.log("virtual2 m()");
        _;
    }
}

contract Virtual2 is IVirtual,IVirtual2 {
    constructor() m{

    }

    modifier m() override(IVirtual,IVirtual2){    //这里重载需要把2个父类显示写出
        console.log("Virtual2 m()");
        _;
    }

    function fun() public override(IVirtual,IVirtual2) m{ //重载需要加override,并且权限得保持一致,不能上面public,下面external
        console.log("local fun2");
    }
}

const { expect } = require("chai");
const { ethers } = require("hardhat");

constractName = "Virtual";
constractName2 = "Virtual2";
describe("contract", function () {
  it("test", async function () {
    const TestContract = await ethers.getContractFactory(constractName);
    const testContract = await TestContract.deploy();
    await testContract.fun();
    const TestContract2 = await ethers.getContractFactory(constractName2);
    const testContract2 = await TestContract2.deploy();
  });
});

  contract
local m()
virtual fun
local m()
local fun
Virtual2 m()