c# 面向对象/继承关系设计

继承

RTTI

RTTI

概念 RTTI(Run Time Type Identification)即通过运行时类型识别，程序能够使用基类的指针或引用来检查着这些指针或引用所指的对象的实际派生类型。

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相关资源

C#高级编程(第11版) Professional C# 7 and .NET Core 2.0

For code comments and issues please check Professional C#'s GitHub Repository

Please check my blog csharp.christiannagel.com for additional information for topics covered in the book.

在ObjectOrientation 章节中有介绍,

但是有些内容没有细讲, 比如纯虚函数的子类如何 在全局变量声明,如何在函数中定义,使用

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c#

父类,子类

1.VirtualMethods

// fish  tail, lungs
// humam  limbs(arms and legs), lungs
// bird wings, lungs
//

public abstract class Organisms
{
        public  Int32 age{get;}

        public virtual void GetAge()
        {
            WriteLine($"moves with {limbs}");
        }

        public abstract void Move( );

}

public class Human: Organisms
{
        public Human()
            : base() { }

        public override void Move( ) // must  override
        {
             WriteLine($"Human: moves with legs   (using limbs when baby age)");
        }

}

public class Kingkong: Organisms
{
        public Human()
            : base() { }

        public override void Move( ) // must  override
        {
             WriteLine($"Kingkong: moves with limbs");
        }

}

public class Fish: Organisms
{
        public Fish()
            : base() { }

         public override void Move( ) // must  override
        {
             WriteLine($"Fish: moves with wings and tail");
        }
}

public class Horse: Organisms //horse  zebra
{
        public Horse()
            : base() { }

        public override void Move( ) // must  override
        {
             WriteLine($"Horse: moves with legs");
        }
}

using System;

namespace VirtualMethods
{
    class Program
    {
        //var _obj = null;  //var 无法在全局变量 声明
        Organisms _Obj =null;

        static void Main()
        {
            var obj = new Human();
            obj.age = 23;
            obj.GetAge();
            obj.Move();

        }
         static void Init()
         {
            _Obj = new Fish();
            _Obj.age = 2;
            _Obj.GetAge();
            _Obj.Move();//父类有abstract function. 所有子类函数必须override,
         }

        static void FuncA()
        {
            Fish fish = _Obj as Fish;//利用全局变量 _Obj
            fish.age = 1;
            fish.GetAge();
            fish.Move();
        }

    }
}

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2.InheritanceWithConstructors

//Shape.cs
using System;

namespace InheritanceWithConstructors
{
    public class Position
    {
        public int X { get; set; }
        public int Y { get; set; }
        public override string ToString() => $"X: {X}, Y: {Y}";
    }

    public class Size
    {
        public int Width { get; set; }
        public int Height { get; set; }
        public override string ToString() => $"Width: {Width}, Height: {Height}";
    }

    public class Shape
    {
        public Shape(int width, int height, int x, int y)
        {
            Size = new Size { Width = width, Height = height };
            Position = new Position { X = x, Y = y };
        }

        public Position Position { get; }
        public Size Size { get; }

        public virtual void Draw() => Console.WriteLine($"Shape with {Position} and {Size}");

        public virtual void Move(Position newPosition)
        {
            Position.X = newPosition.X;
            Position.Y = newPosition.Y;
            Console.WriteLine($"moves to {Position}");
        }
    }
}

//ConcreteShapes.cs

using System;

namespace InheritanceWithConstructors
{
    public class Rectangle : Shape
    {
        public Rectangle(int width, int height, int x, int y)
            : base(width, height, x, y) { }

        public Rectangle()
            : base(width: 0, height: 0, x: 0, y: 0) { }

        public override void Draw() =>
            Console.WriteLine($"Rectangle with {Position} and {Size}");

        public override void Move(Position newPosition)
        {
            Console.Write("Rectangle ");
            base.Move(newPosition);
        }

        public void PrintRectangleFuncA( )//只有Rectangle 才有的函数,其他类没有声明和实现
        {
             Console.Write("Rectangle FuncA ");
        }
    }

    public class Ellipse : Shape
    {
        public Ellipse(int width, int height, int x, int y)
            : base(width, height, x, y) { }

        public Ellipse()
            : base(width: 0, height: 0, x: 0, y: 0) { }
    }
}

//Program.cs

namespace InheritanceWithConstructors
{
    class Program
    {
        Shape _sharp = null;//全局变量
        static void Main(string[] args)
        {
            var r = new Rectangle();
            r.Position.X = 33;
            r.Position.Y = 22;
            r.Size.Width = 200;
            r.Size.Height = 100;
            r.Draw();
            DrawShape(r);

            r.Move(new Position { X = 120, Y = 40 });
            r.Draw();

            Shape s1 = new Ellipse();
            DrawShape(s1);
        }
        public staic void Init()
        {
           _sharp = new Rectangle();//如果_sharp 是全局变量, 让其他地方也可使用此对象 怎么办?
        }
        public staic void FuncA()
        {
          Rectangle rect= _sharp as Rectangle;
          rect.PrintRectangleFuncA(); //只有Rectangle 才有的函数,其他类没有声明和实现,可以这样调用
        }

        public static void DrawShape(Shape shape) => shape.Draw();
    }
}

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3.UsingInterfaces

//基本上和VirtualMethods 类似,但是所有接口类的 子类, 要通用, 子类必须

//IBankAccount.cs
namespace Wrox.ProCSharp
{
    public interface IBankAccount
    {
        void PayIn(decimal amount);//子类必须有实现
        bool Withdraw(decimal amount);//子类必须有实现
        decimal Balance { get; }//子类必须有实现
    }
}

//ITransferBankAccount.cs
namespace Wrox.ProCSharp
{
    public interface ITransferBankAccount : IBankAccount
    {
        bool TransferTo(IBankAccount destination, decimal amount);
    }
}

//JupiterBank.cs

using System;

namespace Wrox.ProCSharp.JupiterBank
{
    public class GoldAccount : IBankAccount
    {
        private decimal _balance;

        public void PayIn(decimal amount) => _balance += amount;

        public bool Withdraw(decimal amount)//Withdraw撤回
        {
            if (_balance >= amount)
            {
                Console.WriteLine($"GoldAccount(IBankAccount): Withdraw(){_balance}");
                _balance -= amount;
                return true;
            }
            Console.WriteLine("GoldAccount(IBankAccount): Withdraw attempt failed.");
            return false;
        }

        public decimal Balance => _balance;

        public override string ToString() =>
            $"GoldAccount(IBankAccount): Balance = {_balance,6:C}";
    }

    public class CurrentAccount : ITransferBankAccount
    {
        private decimal _balance;

        public void PayIn(decimal amount) => _balance += amount;

        public bool Withdraw(decimal amount)
        {
            if (_balance >= amount)
            {
                _balance -= amount;
                return true;
            }
            Console.WriteLine("Withdrawal attempt failed.");
            return false;
        }

        public decimal Balance => _balance;

        public bool TransferTo(IBankAccount destination, decimal amount)
        {
            bool result = Withdraw(amount);
            if (result)
            {
                destination.PayIn(amount);
            }
            return result;
        }

        public override string ToString() =>
          $"Jupiter Bank Current Account: Balance = {_balance,6:C}";
    }
}

//VenusBank.cs

using System;

namespace Wrox.ProCSharp.VenusBank
{
    public class SaverAccount : IBankAccount
    {
        private decimal _balance;

        public void PayIn(decimal amount) => _balance += amount;

        public bool Withdraw(decimal amount)
        {
            if (_balance >= amount)
            {
                _balance -= amount;
                return true;
            }
            Console.WriteLine("Withdrawal attempt failed.");
            return false;
        }

        public decimal Balance => _balance;

        public override string ToString() =>
            $"Venus Bank Saver: Balance = {_balance,6:C}";
    }
}

//Program.cs
namespace UsingInterfaces
{
    class Program
    {
        IBankAccount _golbal_obj =null;//全局变量
        static void Main()
        {
            IBankAccount venusAccount = new SaverAccount();
            IBankAccount jupiterAccount = new GoldAccount();

            venusAccount.PayIn(200);
            venusAccount.Withdraw(100);
            Console.WriteLine(venusAccount.ToString());

            jupiterAccount.PayIn(500);
            jupiterAccount.Withdraw(600);
            jupiterAccount.Withdraw(100);
            Console.WriteLine(jupiterAccount.ToString());

        }

        public static void Init()
        {
            _golbal_obj = new SaverAccount();//用子类去new
        }

        public static void FunA()
        {
            if(_golbal_obj!=null)
            {
               _golbal_obj.PayIn(100);//直接调用SaverAccount 子类的 实现,所以这也是为什么需要子类全部都要实现,
               _golbal_obj.Withdraw(100);//直接调用SaverAccount 子类的 实现
            }
        }

    }
}