Retrieve objects pointers of different type

Question

Consider I have a bunch pointers to to different objects of different classes

class1* obj1;
class2* obj2;
class3* obj3;

and they all have one method getArray() which returns a vector for post processing.

if all of these pointers are stored in some sort of a list (a list of void pointers say)

while I am iterating the list is there a way to figure what type of a pointer cast can be used?

I understand this can be solved by class hierarchy and deriving the above classes from a single class. Since a lot of it is legacy code can something like what is mentioned be done?

Folly dynamic does not let me store pointers, thats one thing that is tried

Answer 1

If getArray() always has the same signature (or similar enough to cast to the same type) - what you could do is create a class hierarchy for a decorator of the duck-typed legacy objects/classes. You can use a template derived class of a non-template interface to wrap without too much typing work.

Something along these lines (with more defensive coding, possibly smart pointers to the legacy object, etc. etc.):

class IDecorator {
  public:
    virtual std::vector<ubyte> GetArray() = 0;
};

template<typename TLegacyType>
class TDecorator : public IDecorator {
   public:
     TDecorator(const TLegacyType *ip_legacy_object)
       : mp_legacy_object(ip_legacy_object) {}
     std::vector<ubyte> GetArray() override {
        return mp_legacy_object->GetArray();
     }

   private:
     const TLegacyType *mp_legacy_object;        
};