การออกแบบ (อินเทอร์เฟซและการสืบทอด)

ภาพรวมโปรเจกต์

เริ่มจากสัญญา

using System;

// Interface: minimal behavior all shapes must provide
public interface IShape
{
  double Area();
  double Perimeter();
}

// A tiny helper to print any IShape
public static class ShapePrinter
{
  public static void Print(IShape s)
  {
    Console.WriteLine("A=" + s.Area() + " P=" + s.Perimeter());
  }
}

public class Program
{
  public static void Main(string[] args)
  {
    // No concrete shapes yet; interface compiles and is ready.
    Console.WriteLine("Shape API ready");
  }
}

คลาสฐานเสริม

using System;

// Optional base for helpers; interface stays the main contract
public abstract class ShapeBase : IShape
{
  public abstract double Area();
  public abstract double Perimeter();

  // Shared rounding helper
  protected double Round2(double x)
  {
    return Math.Round(x, 2);
  }
}

public class Program
{
  public static void Main(string[] args)
  {
    Console.WriteLine("Base class prepared for shared helpers");
  }
}

รูปทรงที่นำไปใช้ได้จริง

using System;

public interface IShape
{
  double Area();
  double Perimeter();
}

public class Rectangle : IShape
{
  private readonly double _w, _h;
  public Rectangle(double w, double h) { _w = w; _h = h; }
  public double Area() { return _w * _h; }
  public double Perimeter() { return 2 * (_w + _h); }
}

public class Circle : IShape
{
  private readonly double _r;
  public Circle(double r) { _r = r; }
  public double Area() { return 3.14159 * _r * _r; }
  public double Perimeter() { return 2 * 3.14159 * _r; }
}

public class Program
{
  public static void Main(string[] args)
  {
    IShape a = new Rectangle(3, 4);
    IShape b = new Circle(2);
    Console.WriteLine("Rect A=" + a.Area() + " P=" + a.Perimeter());
    Console.WriteLine("Circ A=" + b.Area() + " P=" + b.Perimeter());
  }
}

กลุ่มข้อมูลของ IShape

using System;
using System.Collections.Generic;

public interface IShape
{
  double Area();
  double Perimeter();
}

public class Rectangle : IShape
{
  private readonly double _w, _h;
  public Rectangle(double w, double h) { _w = w; _h = h; }
  public double Area() { return _w * _h; }
  public double Perimeter() { return 2 * (_w + _h); }
}

public class Circle : IShape
{
  private readonly double _r;
  public Circle(double r) { _r = r; }
  public double Area() { return 3.14159 * _r * _r; }
  public double Perimeter() { return 2 * 3.14159 * _r; }
}

public class Program
{
  public static void Main(string[] args)
  {
    List<IShape> shapes = new List<IShape>();
    shapes.Add(new Rectangle(2, 5));
    shapes.Add(new Circle(1.5));

    foreach (IShape s in shapes)
    {
      Console.WriteLine("A=" + s.Area() + " P=" + s.Perimeter());
    }
  }
}

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