c++ - 带有子类的类的纯接口(interface)

Question

假设你想创建一个 Derived 类的接口(interface)，它看起来像这样:

class Derived : public Base
{
   public:
      foo();
}

class Base
{
   public:
      tii();
      //many other methods
}

你会如何做界面？如何使 Base::tii 对这个新界面可见(以及其他方法)？

class IDerived
{
   public:
      virtual foo() = 0;
      // should I declare here tii() as a pure virtual function?
      // but by doing it now there is ambiguity!
}

什么是好的策略？

新的派生类应该是这样的....

class Derived : public Base, public IDerived
{
    //implement the real thing    
}

Answer 1

您的示例是倒退的:接口(interface)应该独立于任何具有所有纯虚拟方法的具体类来定义:

class IDerived
{
   public:
      virtual void foo() = 0;
      virtual ~IDerived() {} // don't forget to include a virtual destructor
}

具体类将从接口(interface)公开派生:

class Derived : public Base, public IDerived
{
   public:
      void foo();
}

如果您希望 IDerived 也声明 Derived 继承自 Base 的方法，您可以显式地使用 Derived通过调用继承的实现来实现该方法:

class Derived : public Base, public IDerived
{
   public:
      void foo();
      void bar() { Base::bar(); } 
}