接口是迫使从它继承的类必须实现某些功能或变量的方法。函数不能在一个接口来实现，因为它们在从接口继承的类总是执行。使用interface关键字代替，尽管两者在很多方面是相似的class关键字创建一个接口。当你想从一个接口继承和类已经从另一个类继承，那么需要单独的类的名称，并用逗号将接口的名称。
让我们来看一个简单的例子，说明使用的接口。
| import std.stdio; |
| // Base class |
| interface Shape |
| { |
| public: |
| void setWidth(int w); |
| void setHeight(int h); |
| } |
| // Derived class |
| class Rectangle: Shape |
| { |
| int width; |
| int height; |
| public: |
| void setWidth(int w) |
| { |
| width = w; |
| } |
| void setHeight(int h) |
| { |
| height = h; |
| } |
| int getArea() |
| { |
| return (width * height); |
| } |
| } |
| void main() |
| { |
| Rectangle Rect = new Rectangle(); |
| Rect.setWidth(5); |
| Rect.setHeight(7); |
| // Print the area of the object. |
| writeln("Total area: ", Rect.getArea()); |
| } |
Total area: 35
一个接口可以有最终的和静态方法的定义应包括在接口本身。这些功能不能过度由派生类重载。一个简单的例子如下所示。
| import std.stdio; |
| // Base class |
| interface Shape |
| { |
| public: |
| void setWidth(int w); |
| void setHeight(int h); |
| static void myfunction1() |
| { |
| writeln("This is a static method"); |
| } |
| final void myfunction2() |
| { |
| writeln("This is a final method"); |
| } |
| } |
| // Derived class |
| class Rectangle: Shape |
| { |
| int width; |
| int height; |
| public: |
| void setWidth(int w) |
| { |
| width = w; |
| } |
| void setHeight(int h) |
| { |
| height = h; |
| } |
| int getArea() |
| { |
| return (width * height); |
| } |
| } |
| void main() |
| { |
| Rectangle rect = new Rectangle(); |
| rect.setWidth(5); |
| rect.setHeight(7); |
| // Print the area of the object. |
| writeln("Total area: ", rect.getArea()); |
| rect.myfunction1(); |
| rect.myfunction2(); |
| } |
Total area: 35 This is a static method This is a final method
