c++ - Vector in an abstract class

Question

I believe that the question here is similar however I still need more clarification on it.

Let's say I create a vector inside an abstract class (which stores objects of another class). How would I be able to use .pushback() from another class if I can't initialise an object of an abstract class?

Obviously the easiest solution is to put the vector in another class but I need another way. I've read you can do this by storing pointers to those objects in a vector. But can somebody give me an example please?

标签： c++vector

Answer 1

The purpose of an abstract class is to provide an interface that is then implemented in concrete derived classes.

If you want to push items onto the vector which is a data member of the abstract class, then create an appropriate derived class and then you can create an instance of that derived class, which will thus contain a vector you can add entries to.

class Base{
public:
  virtual void do_stuff()=0; // this is an abstract base class
protected:
  std::vector<int> data;
};

class Derived: public Base
{
public:
  void do_stuff() {
    // concrete implementation
    data.push_back(42); // can add values to vector inherited from base class
  }
};

int main()
{
  Derived d;
  d.do_stuff(); // will add entries to d.data
}

However, I wonder if that is really what you are trying to achieve.