第3章 面向对象技术7

第七讲接口？为什么引入接口。

组件技术，组件对象模型COM, COM+ 事务服务器MTS , 应用程序编程接口API.7.1接口抽象类--------〉接口1、接口类似纯抽象类。

2、接口不提供任何实现的代码，提供规范，不提供细节。

3、接口成员只包含方法，属性和索引器，不包含数据成员。

7.1.2使用接口1、类可以实现多个接口。

2、解决了多重继承问题。

7.1.3使用接口的好处1、多重继承2、给类添加了固定的特征，并必须实现之。

7.2定义接口基本结构：Interface Iname{接口成员；}说明：借口中的成员是公有的，（public）.7.2.1定义带方法成员的接口定义一个接口Public interface Isharp{double Area();double Circumference();Int Sides();}例：using System;public interface IShape{ double Area();double Circumference();Int Sides();}public class Circle : IShape{ public int x;public int y;public double radius;private const float PI = 3.14159F;public double Area() //每个方法的参数类型和接口必须保持一致{ double theArea;theArea = PI * radius * radius;return theArea; }public double Circumference(){ return ((double) (2 * PI * radius));}public int Sides(){ return 1;}public Circle(){ x = 0;y = 0;radius = 0.0;}}public class Square : IShape{public int side;public double Area(){return ((double) (side * side));}public double Circumference(){return ((double) (4 * side));}public int Sides(){return 4;}public Square(){side = 0;}}public class myApp{public static void Main(){Circle myCircle = new Circle();myCircle.radius = 5;Square mySquare = new Square();mySquare.side = 4;Console.WriteLine("Displaying Circle information:");displayInfo(myCircle);Console.WriteLine("\nDisplaying Square information:");displayInfo(mySquare);}static void displayInfo( IShape myShape ) //能接受任何实现了接口的对象。

{Console.WriteLine("Area: {0}", myShape.Area());Console.WriteLine("Sides: {0}", myShape.Sides());Console.WriteLine("Circumference: {0}", myShape.Circumference());}}7.2.2在接口中指定属性接口中包含有关属性的规范。

无需实现。

例:限定符数据类型属性名{Get;Set;}实例：using System;public interface IShape{int Sides // 定义属性规范{get;set;}double Area();}public class Square : IShape{private int sides;public int SideLength;public double Area(){return ((double) (SideLength * SideLength));}public int Sides{get { return sides; } 1、//可以缺少吗？set { sides = value; }}public Square(){Sides = 4;}}public class myApp{public static void Main(){Square mySquare = new Square();mySquare.SideLength = 5;Console.WriteLine("\nDisplaying Square information:");Console.WriteLine("Area: {0}", mySquare.Area());Console.WriteLine("Sides: {0}", mySquare.Sides);}}实验1 在接口中定义只读属性、只写属性，实现时应注意什么？编写程序说明之。

7.3使用多个接口看例子：Class Square : Ishape,IshapeDisply{….}实例：using System;public interface Ishape //定义接口Ishape{ double Area();int Sides { get; }}public interface IshapeDisplay //定义接口IshapeDisplay{ void Display();}public class Square : IShape, IShapeDisplay{ private int sides;public int SideLength;public int Sides{get { return sides; }}public double Area(){return ((double) (SideLength * SideLength));}public double Circumference(){return ((double) (Sides * SideLength));}public Square(){sides = 4;}public void Display(){Console.WriteLine("\nDisplaying Square information:");Console.WriteLine("Side length: {0}", this.SideLength);Console.WriteLine("Sides: {0}", this.Sides);Console.WriteLine("Area: {0}", this.Area());}}public class myApp{public static void Main(){Square mySquare = new Square();mySquare.SideLength = 7;mySquare.Display();}}7.4显式接口成员？若接口成员名称和已有名称相同时会出现什么情况A:只需要实现一次例：using System;public interface A{double Area();int Sides { get; }void Display();}public interface B{void Display();}public class Square : A, B{private int sides;public int SideLength;public int Sides{get { return sides; }}public double Area(){return ((double) (SideLength * SideLength));}public double Circumference(){return ((double) (Sides * SideLength));}public Square(){sides = 4;}void A.Display() //显式实现{Console.WriteLine("\nDisplaying Square Shape\'s information:");Console.WriteLine("Side length: {0}", this.SideLength);Console.WriteLine("Sides: {0}", this.Sides);Console.WriteLine("Area: {0}", this.Area());}void B.Display() //显式实现{Console.WriteLine("\nThis method could draw the shape...");}}public class myApp{public static void Main(){Square mySquare = new Square();mySquare.SideLength = 7;A sa = (A) mySquare; //显式转换B sb = (B) mySquare; //显式转换sa.Display();sb.Display();}}7.5 从已有接口派生出新的接口public interface IShape{ double Area();double Circumference();Int Sides();}interface I3Dshape : IShape{Int Depth{get; set;};}？可否有覆盖和重载现象作业：？7.6 隐藏接口成员using System;public interface IShape{int ShapeShifter( int val );int Sides { get; set; }}public class Shape : IShape{private int sides;public int Sides{get { return sides; }set { sides = value; }}int IShape.ShapeShifter( int val )//隐藏了方法{Console.WriteLine("Shifting Shape....");val += 1;return val;}public Shape(){Sides = 5;}}public class myApp{public static void Main(){Shape myShape = new Shape();Console.WriteLine("My shape has been created.");Console.WriteLine("Using get accessor. Sides = {0}", myShape.Sides);// myShape.Sides = myShape.ShapeShifter(myShape.Sides); // error 不能直接访问IShape tmp = (IShape) myShape; //强制转换myShape.Sides = tmp.ShapeShifter( myShape.Sides);Console.WriteLine("ShapeShifter called. Sides = {0}", myShape.Sides);}}补充：组织应用程序C# 程序是通过使用名字空间来组织的，名字空间即可以作为应用程序的内部结构体系，也可以作为应用程序的外部结构体系。