Modern C++ Programming Cookbook

There's more...

When objects of types implementing the CRTP need to be stored homogeneously in a container, an additional idiom must be used. The base class template must be itself derived from another class with pure virtual functions (and a virtual public destructor). To exemplify this on the control class, the following changes are necessary:

    class controlbase    {    public:      virtual void draw() = 0;      virtual ~controlbase() {}    };    template <class T>    class control : public controlbase    {    public:      virtual void draw() override      {        static_cast<T*>(this)->erase_background();        static_cast<T*>(this)->paint();      }    };

There are no changes required to the derived classes, such as button and checkbox. Then, we can store pointers to the abstract class in a container, ...