why doesn't subclass variable get changed when called superclass methods c++ - c++

Question

class LinkedList : public IDataList {
public :
Node *head;
Node* lastNode;
int _size = 0;
public : LinkedList() {
this->head = nullptr;
this->lastNode = nullptr;
}
void deAppend(int data) override;
};
Then I have a circular linkedList which is the subclass of LinkedList
class CircularLinkedList : public LinkedList {
public :
Node *head;
Node* lastNode;
int _size = 0;
public : CircularLinkedList() {
this->head = nullptr;
this->lastNode = nullptr;
}
void deAppend(int data) override;
};
This is the method deAppend which adds to the front of the list
void LinkedList::deAppend(int data){
if (this->head== nullptr){
Node *newNode = new Node(data, nullptr);
this->head = newNode;
this->lastNode = newNode;
}else{
Node *newNode = new Node(data, this->head);
this->head = newNode;
}
this->_size+=1;
}
This is my CiruclarLinkedList calling deAppend method
void CircularLinkedList::deAppend(int data) {
LinkedList::deAppend(data);
this->lastNode->next = this->head;
}
The fact is why doesn't the lastNode and the head of CircularLinkedList variables change even though I am calling the method LinkedList::deAppend(data) and changing them in there. IDataList is just an interface.
class IDataList {
public:
virtual void deAppend(int data) = 0;
};
Picture of Variables assignments after the method is called

Answer 1

I think you are declaring your variables twice. I mean inside your base class you declare:
public:
Node *head;
Node* lastNode;
int _size = 0;
When a class inherits from another class publicly, all the public variables of the base class are also declared in the sub class. Which means you already had these variables in your CircularLinkedList class but you declared them again. Now you have two of them and you're changing the ones from your base class. remove the declaration from CircularLinkedList.