c++ - 如何正确扩展接口(interface)？

Question

我有基于另一个的界面:

class IDrawable {
public:
   virtual ~IDrawable();
};

class IExtendedDrawable: public IDrawable {
public:
   virtual ~IExtendedDrawable();
};

class DrawableImplementation: public IDrawable {
public:
   virtual ~DrawableImplementation();
};

class ExtendedDrawableImplementation: 
   public DrawableImplementation, public IExtendedDrawable
{
public:
   virtual ~ExtendedDrawableImplementation();
};

然后ExtendedDrawableImplementation = DrawableImplementation(+IDrawable) + IExtendedDrawable(+IDrawable)

在同一个类中有两次IDrawable是否正确？

Answer 1

我会怀疑您确实需要/想要多重继承。我只在有限的情况下认为它很好，接口(interface)就是其中之一(甚至 Java 也允许这样做)。

如上所述，使用虚拟继承并确保在接口(interface)类es中只使用纯虚拟方法。

class IDrawable {
public:
   virtual ~IDrawable();
   virtual void doSomething() = 0;
};

class IExtendedDrawable: virtual public IDrawable {
public:
   virtual ~IExtendedDrawable();
   virtual void doSomethingElse() = 0;
};

class DrawableImplementation: virtual public IDrawable {
public:
   virtual ~DrawableImplementation();
   virtual void doSomething() {/*code here*/}
};

class ExtendedDrawableImplementation: 
   public DrawableImplementation, public IExtendedDrawable
{
public:
   virtual ~ExtendedDrawableImplementation();
   virtual void doSomething() {/*code here*/}
   virtual void doSomethingElse() {/*code here*/}
};