Avoid re-implementation of a method call in each derived class

Question

I have an abstract class, and its derived classes.

I want to have a member (i.e. fDerivedName) at the abstract class with the name of the derived class.

In the constructor of each derived class I do :

fDerivedName = this->ClassName();

There is a way to avoid the re-implementation of this in each derived class?

Thanks

Yes. CRTP. It isn't clear why you need `fDerivedName` at all when you can just call `ClassName()` directly, but yes, if you need it you can have it. — n. m. could be an AI, Dec 08 '16 at 10:54
@n.m. I'm not sure how the CRTP would retrieve the derived class name. Or are you thinking of `typeid` ? — Quentin, Dec 08 '16 at 11:02
@Quentin I assume ClassName() is implemented somehow (typeid or not). If it's not the case, then "how to implement ClassName()" is a different question. — n. m. could be an AI, Dec 08 '16 at 11:05
Possible duplicate of [Virtual Function During Construction Workaround](http://stackoverflow.com/questions/23302950/virtual-function-during-construction-workaround) — Trevir, Dec 08 '16 at 11:18
Have a look at the C++ FAQs: https://isocpp.org/wiki/faq/strange-inheritance#calling-virtuals-from-ctor-idiom — Trevir, Dec 08 '16 at 11:19

score 1 · Answer 1 · answered Dec 08 '16 at 11:23

You can implement a constructor in the base class (which is then not pure abstract anymore), pass the name of the derived class as parameter and do your assignment in the initializer list of the constructor:

class Base
{
public:
   Base( const std::string& derived_class_name):
      fDerivedName( derived_class_name)
   {
   }
   ...
};

But, of course, you still have to call this base class constructor from each constructor of your derived classes. And you will have to pass the class name as parameter, you cannot e.g. call a virtual function ClassName() overloaded by the derived classes.

Avoid re-implementation of a method call in each derived class

1 Answers1