Right design pattern to deal with polymorphic collections of objects

Question

Suppose I have the following classes:

class BaseObject {
    public:
        virtual int getSomeCommonProperty();
};

class Object1: public BaseObject {
    publ         


        

Answer 1

Maybe this will do the trick here ?

class CollectionManipulator {
public:
    void someCommonTask(BaseCollection& coll) {
         for(unsigned int i = 0; i < coll.size(); i++)
              someCommonTask(coll.getObj(i));
    }
private:
    void someCommonTask(BaseObject*);  // Use baseObjects

};

class BaseCollection {
     friend class CollectionManipulator;
private:
     virtual BaseObject* getObj(unsigned int) = 0;
     virtual unsigned int size() const = 0;
};

class Collection1 : public BaseCollection {
    vector objects;

public:
    virtual void addObject() {
        Object1* obj = new Object1;
        objects.push_back(obj);
        baseObjects.push_back(obj);
    }

    void someSpecificTask(); // Use objects, no need of dynamic_cast<>

private:
    BaseObject* getObj(unsigned int value) {
        return object[value];
    }

    unsigned int size() const {
        return objects.size();
    }
}

If you want abstract your container in Collection1 (like using list instead using vector), to use it in Manipulator, create an abstract iterator...