destructors

**Bones** · 09-17-2003

In my program I have to put a destructor in the class which will delete all the links when a linklist object is distroyed. I have to delete each link as it goes, displaying a message that the element was destoryed.....this is the code for the class....

Code:

////////////////////////////////////////////////////////////////
struct link                                             //one element of list
{
        int data;                                       //data item
        link* next;                                     //Pointer to next link
};
////////////////////////////////////////////////////////////////
class linklist
{
        private:
                link* first;                            //pointer to first link
        public:
                linklist() : first(NULL)
                { }

                void additem(int d);
                void display() const;


};
//--------------------------------------------------------------
void linklist::additem(int d)
{
        link* newlink = new link;                       //make a new link
        newlink->data = d;                              //give it data
        newlink->next = first;                          //it points to next link
        first = newlink;                                //now first points to this
}
//---------------------------------------------------------------
void linklist::display() const
{
        link* current = first;                          //set ptr to first link
        while(current != NULL)                          //quit on last link
        {
                cout<<current->data <<endl;             //print data
                current = current->next;                //move to next link

        }

}

////////////////////////////////////////////////////////////////

Anyhelp on where this destructor goes would be great.

Cheers

**confuted** · 09-17-2003

You'll need something like this:

Code:

if next
     delete next

in the destructor, as well as the message displaying that the element was deleted. Figure out why this works - it's good for you.

Oh, and the placement of the destructor in the file doesn't matter.

void linklist::~linklist()

**...** · 09-17-2003

ive always been taught to do this with my linked lists:

you will probably want a function to remove a node from the end of your list. i would make its prototype like this:

template <typename Type>
bool remove( Type &t );

where type is the type of variable the list holds. the way it works is, you pass a variable in to t to store the data of the node youre deleting, and then you return true if a node was deleted or false if the list is empty.

then all you have to do in your destructor is call the remove function in a while loop until it returns false. i usually would make a dummy variable to hold the value, just so the function has the argument it needs.

Code:

List::~List()
{
   Type temp
   while ( remove(temp) );
}

**HybridM** · 09-18-2003

how about something like:

Code:

while(count) // while there are nodes
{
    RemoveNode; // call the function you normally call when deleting a node
                //this should also decrement count
}

This is assuming you're keeping a counter in your list class of how many nodes you have.

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