【開發智能合約 — Solidity系列】實作篇Ep.9 — 何謂繼承(Inheritance)

基本用法

// 合約B繼承自A
contract B is A {
   ...
}

繼承自單一的來源

首先我們先撰寫一份公共合約

contract Basic {
   string public title;   constructor(string memory _title) {
       title = _title;
   }   function getTitle() public view returns(string memory) {
       return title;
   }
}

撰寫一份Basic0合約繼承自Basic並帶入初始值

contract Basic {
   ...
}// 繼承自Basic並帶入初始化參數
contract Basic0 is Basic("i am Basic0") {}

撰寫一份Basic1合約繼承自Basic並由外部帶入初始值

contract Basic {
   ...
}// 繼承自Basic並支援外部帶入參數至Basic
contract Basic1 is Basic {
    constructor(string memory _title) Basic(_title) {    }
}

多重繼承

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.7.0;contract Basic {
   string public basic = "basic";
   ...
}// 繼承自Basic並帶入初始化參數
contract Basic0 is Basic("i am Basic0") {
    string public basic0 = "basic0";
}contract Basic2 is Basic, Basic0 {
     // 定義事件並接收msg參數
   event Log(string msg);    function test() public {
        emit Log(basic);
        emit Log(basic0);
    }
}

結語