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c++ooptemplatesidioms

C++ idiom (or pattern) with interheritance from `NameBase` class to template `Name` class

From time to time I come across the following (or something like that) class hierarchy in different C++ projects:

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

template<typename T>
class Dummy : public DummyBase
{
    public:
        void doSomething() override
        {
            ...
        }

    private:
        T field;
};

Looks like as C++ idiom, pattern or maybe trick. Can you tell me the purpose of this contruction and what's the problem can be solved using it. I would be glad to read good articles or maybe books that describe it.

Solution

  • This is polymorphism based type erasure, it is often used for handling things like std::function or std::any which can store data of unrelated types in the exact same manner (e.g. function pointers and member function pointers for std::function).