關於基類中函數修飾符abstract和virtual的使用

關於基類中函數修飾符abstract和virtual的使用

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Computer.Qualifier
{
    //關於基類中函數修飾符abstract和virtual的使用
    class Program
    {
        static void Main(string[] args)
        {
            //V1
            //Hint: The best way is just by sony or lenove//第一個版本V1我使用此方式

            //V2
            //開始爲了寫普通方法->簡單工廠->工廠方法->抽象工廠->......
            //竟然寫着寫着就寫到多態了，多態和重載不是一個概念，重載是指同名函數的參數類型不同或者參數個數不同，與返回類型無關。
            //而多態是指同名函數，不但參數類型和參數個數相同，還有返回類型也相同，只是函數的修飾符不同。
            //最終決定調用基類還是子類，abstract/virtual/override/new要比上面的情況複雜。
            //註釋中的"//right"只是說在通常情況下使用最多的方式，“//bad”則反之。

            //Hint: The best way is just by Dell or IBM//第二個版本V2，後面幾篇文都是基於這個講解，所以在這個版本我把修飾符換了

            PC pc;
            //pc.Name = "NA PC";
            //pc = new Dell("");
            pc = new Dell("Dell");
            pc.Name = "OtherDell";
            pc.Describe();


            System.Console.WriteLine();
            pc = new IBM("IBM");
            pc.Name = "OtherIBM";
            pc.Describe();

            System.Console.WriteLine();
            pc = new HP("HP");
            pc.Name = "OtherHP";
            pc.Describe();

            System.Console.WriteLine();
            pc = new Sony("Sony");
            pc.Name = "OtherSony";
            pc.Describe();


            System.Console.WriteLine();
            pc = new Lenovo("Lenovo");
            pc.Name = "OtherLenovo";
            pc.Describe();
        }
    }

    abstract class PC//:Brand
    {
        //注意這篇文章中這裏使用了protected，和後面文章中的改用成private有很大的不同
        protected string name;

        //public PC(string name){ } //bad, sub-class need tranfer this.name=name

        public PC(string name)      //right, sub-calss needn't tranfer this.name=name
        {
            //this.name = "unknown";   
            this.name = name;
            //this.name = !string.IsNullOrEmpty(name) ? name : "unknown";
        }

        //The super-class property(Name{get;set;}) don't use abstract,otherwise the sub-class(Dell/IBM/...) must implement Name{get;set;}
        //public abstract string Name { get; set; } //bad
        public virtual string Name { get; set; }    //right        

        //public abstract void Describe();       //right 
        public virtual void Describe() { System.Console.WriteLine("I am {0} personal computer of super-calss", name); }    //bad
    }

    class Dell : PC
    {
        public Dell(string name) : base(name)
        {
            //this.name = name; //no use tranfer
        }

        public override void Describe()
        {
            System.Console.WriteLine("I am {0} personal computer", name);
            System.Console.WriteLine("I am {0} personal computer", Name);
        }
    }

    class IBM : PC
    {
        protected new string name;  //No, or have to use it(要麼不用，要麼必須這樣用),此處的成員變量(name)只能這樣new基類同名成員變量

        //the qualifier(override/new) don't use new, otherwise will call super-class
        public override string Name { get; set; }    //right, use override, it's call sub-class

        public IBM(string name) : base(name)
        {
            this.name = name;
        }

        public override void Describe()             //right, use override, it's call sub-class
        {
            System.Console.WriteLine("I am {0} personal computer", name);
            System.Console.WriteLine("I am {0} personal computer", Name);
        }
    }

    class HP : PC
    {
        protected new string name;
        public override string Name { get; set; }   //right

        public HP(string name) : base(name)
        {
            this.name = name;
        }

        
        public new void Describe()                  //bad
        {
            System.Console.WriteLine("I am {0} personal computer", name);
            System.Console.WriteLine("I am {0} personal computer", Name);
        }
    }

    class Sony : PC
    {
        protected new string name;
        public new string Name { get; set; }        //bad

        public Sony(string name) : base(name)
        {
            this.name = name;
        }

        public override void Describe()             //right
        {
            System.Console.WriteLine("I am {0} personal computer", name);
            System.Console.WriteLine("I am {0} personal computer", Name);
        }
    }

    class Lenovo : PC
    {
        protected new string name;
        public new string Name { get; set; }        //bad

        public Lenovo(string name) : base(name)
        {
            this.name = name;
        }

        public new void Describe()                  //bad
        {
            System.Console.WriteLine("I am {0} personal computer", name);
            System.Console.WriteLine("I am {0} personal computer", Name);
        }
    }
}

版權所有，轉載請註明文章出處 http://blog/csdn.net/cadenzasolo