[FIXED] how to access class private data members in method parameter of class , i get an error invalid use of non static data members

Issue

i have two classes Node and AvlTree , i will make other methods of AvlTree later but i can't access root data member of AvlTree in it's own class , how can i access root in AvlTree class inOrder method.

My code is following here

class Node {
    public:
        int key;
        Node* left;
        Node* right;
        int height;

        Node(int key) : key(key) , left(nullptr) , right(nullptr) , height(1) {};
};

class AvlTree {
    private:
        Node* root;
    public:
        AvlTree() : root(nullptr) {};

        int height(Node* ptr) {
            
        }

        int getBalanceFactor(Node* ptr) {
            
        }

        void inOrder(Node* itr = root) {      // <--- i get an error here

        }
};

I tried with this->root but that also does't work , what i am do wrong here , also can i not access like this in it's own class. I got an error like

09_avl_tree.cpp:36:34: error: invalid use of non-static data member ‘AvlTree::root’
   36 |         void inOrder(Node* itr = root) {
      |                                  ^~~~
09_avl_tree.cpp:15:15: note: declared here
   15 |         Node* root;
      |               ^~~~

I don't want to make root as static data member. because i want multiple instances of AvlTree.

Solution

The short answer, as the compiler is telling you, is that you can't do that as a default value of an argument.

The simplest approach would be to overload the inOrder() function, for example (within the definition of AvlTree)

  void inOrder(Node *itr)
  {
        // whatever
  }

  void inOrder()
  {
       inOrder(root);
  }
  

Also, unrelated to your question, the shadowing of member names in Nodes constructor (e.g. an argument named key used to initialise a member named key) is not a good idea, since it is easy to mislead human readers about what the code does. It is therefore often considered preferable to name the argument differently from the member.

Answered By - Peter

Answer Checked By - Mildred Charles (PHPFixing Admin)