Question

Into a class constructor, I need to create some objects on the fly and add them to a vector. Here is my code:

ContainerClass::ContainerClass() {
   for (int i = 0; i < limit; i++)
      elements.push_back(SubElement());
}

Is this the same thing with new SubElement()? Do I still need to free those SubElement() objects into the ContainerClass destructor?

Answer 1

Method 1:

If you have std::vector<SubElement> elements;
Then you would use elements.push_back(SubElement()).

SubElement() creates a SubElement on the stack and then a copy gets added to the vector.

You should NOT call delete on the individual elements of the vector. They will be destructed and deallocated when the vector goes out of scope.

Method 2:

If you have std::vector<SubElement*> elements;
Then you would use elements.push_back(new SubElement()).

new SubElement() creates a SubElement on the heap, and then the address of that element gets stored in the vector.

You would need to call delete on the individual elements before the vector goes out of scope, otherwise you’ll create a memory leak. They will be destructed and deallocated only when you call delete on each of the elements.