CODEWITHSUNDEEP
c++destructor
nc052
nc052

Reputation: 47

C++ doubly linked list: How to show that Destructor is implemented correctly

Basically, I have created a doubly linked list and now need to show that the destructor is implemented and tested back in main.cpp (int main).

It was suggested in the assignment that I should create a function, as well as to place a cout statement that outputs the address of each node right before it is deleted. I am not sure how I should go by doing this.

So far, I have created a function like this:

void cList() {
    DoublyLinkedList a
    cout << "ex: 0 1 2 3" << endl;
    for (unsigned i = 0; i < 4; i++) {
        a.push_back(i);
    }
    cout << "Display in function: ";
    a.display();
    cout << endl;

    //this shows the addresses of each node
    cout << "delete addresses: " << endl;
    for (it = del.begin(); it!=del.end(); ++it) {
        cout << &it << endl;
    }
}

I understand that when the list is out of scope, the destructor will be called. I have a cout statement back in the ~DoublyLinkedList that says "destructor called". When I do this, the "destructor called" statement is outputted after the addresses are displayed. But how do I fulfill the requirement by displaying the address before it is deleted? Thank you.

Sample Output:

delete addresses:
0x7ffeb484d300
0x7ffeb484d300
0x7ffeb484d300
0x7ffeb484d300
Destructor Called

Upvotes: 1

Views: 896

Answers (2)

gchen
gchen

Reputation: 1173

You can put this part into the destructor:

cout << "delete addresses: " << endl;
    for (it = del.begin(); it!=del.end(); ++it) {
        cout << &it << endl;
    }

so the output of deleted nodes will be automatically shown when the function ends.

//This is assuming you aren't using any sentinel head/tail pointers.
~DoublyLinkedList() {
        cout << "delete addresses: " << endl;

        Node* nextNode = nullptr;

        while(headPtr) {
            nextNode = headPtr->next;
            cout << headPtr << endl;
            delete headPtr;
            headPtr = nextNode;
        }
        cout << "Destructor Called" << endl;
    }

Upvotes: 0

Cory Kramer
Cory Kramer

Reputation: 117856

Your constructor can output the object as it is created:

Node::Node()
{
    std::cout << "Creating node: " << this << std::endl;
}

then your destructor can output the opposite as it is destroyed

Node::~Node()
{
    std::cout << "Destroying node: " << this << std::endl;
}

Then you don't need to delete anything in main. You just need to make sure your destructor for DoublyLinkedList goes through and destroys all the Node objects. Then when DoublyLinkedList a falls out of scope you'll see your output from the destructors.

Upvotes: 3

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