Programming Forums - Linked List Of Objects

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Linked List Of Objects

Hi,

I need to be able to hold a linked list of pointers to objects of a class I made myself. I know to add to a linked list something like this:

        //construction

        LinkedList();



        //add a new node to the last

        void addToList(int *data);

Just wondering what I replace the (int *data) part with?

Cheers

replace the int with the data type you are wanting to save to your linked list ? not quite sure if get what you mean. are all the objects of the same type ?

Sorry for not explaining myself very well.

I have a class Vehicle so in my code I have a line like...



Vehicle *myVeh = new Vehicle;

So that's what I want to store in the linkedlist, the myVeh pointer. NOt sure what I would replace int with.

void addToList(Vehicle *data); ?

I'm assuming that the current implementation you are using are storing pointers to integer values ?

void addToList( new Vehicle(...) );

or just pass the addToList myVeh.

oooh Dawei, I saw that post before you removed it ;)

LOL. It was a virtual duplicate, including the time stamp.

Quote:

Originally Posted by DaWei (Post 127844)

LOL. It was a virtual duplicate, including the time stamp.

aye virtually... apart from the syntax error of course. :p I'll catch you out some day.

That is what I thought was very unsure though.

I tried it and now I get this Error:

error C2664: 'Node::setData' : cannot convert parameter 1 from 'Vehicle *' to 'int *'

The code around the error location is...



void LinkedList::addToList(Vehicle *data)

{

        Node *newNodePtr;



        //craete new instance of Node

        newNodePtr = new Node;



        //set data

        newNodePtr->setData(data);      <<< ERROR LINE <<<



        //check if list is empty

        if( _begin == NULL) 

        {

                _begin = newNodePtr;

        }

        else

        {

                newNodePtr->setPrevNode(_end);

                _end->setNextNode(newNodePtr);

        }



        //set current pointer end end pointer

        _end = newNodePtr;

        _current = newNodePtr;

}

Any idea?

yeah, you haven't changed the node to take a pointer to a Vehicle. You will need to change whatever it is in your Node class that is int * to Vehicle *.
At current you are trying to set a Pointer of an Integer type to a pointer of a Vehicle type.
If you are still stuck, show me your Node class and I'll show you where.

Hi, thanks a lot for your replies, tried a few things but can't seem to get it right.

here's my code

list.h...

#include "vehicle.h"



//forward declaration

class Node;



//class definition

class LinkedList

{

public:

        //construction

        LinkedList();



        //add a new node to the last

        void addToList(int *data);



        //find an element in list and set current pointer

        void find( int key);



        //get data from element pointed at by current pointer

        int* getCurrent(void);



        //delete element pointed at by current pointer

        void deleteCurrent(void);



private:

        //data members

        Node *_begin;                //pointer to first element in list

        Node *_end;                //pointer to last element in list

        Node *_current;        //pointer to current element in list

};

list.cpp



#include "stdafx.h"

#include <iostream>

using namespace std;



//class definition



#define NOT_IN_LIST "not in list"



class Node

{

public:

        //construction and destruction

        Node();

        ~Node();



        //to set and get the next node in the list

        void setNextNode(Node *next);

        Node* getNextNode(void);



        //to set and get the previous node in the list

        void setPrevNode(Node *next);

        Node* getPrevNode(void);



        //to set and access data hold in node

        void setData(int *data);

        int* getData(void);



private:

        //data members

        Node *_next;        //pointer to next node in list

        Node *_prev;        //pointer to previous node in list

        int *_data;        //pointer to data hold in node

};







Node::Node()

{

        //initialise the next and previous node pointers

        _next = NULL;

        _prev = NULL;



        //initialise the data pointer

        _data = NULL;

}









Node::~Node()

{

        //delete data that is hold in node

        delete _data;

}







void Node::setNextNode(Node *ptr)

{

        //next node pointer points to new location

        _next = ptr;

}









Node* Node::getNextNode(void)

{

        //return pointer to next node

        return _next;

}













void Node::setPrevNode(Node *ptr)

{

        //previous node pointer points to new location

        _prev = ptr;

}









Node* Node::getPrevNode(void)

{

        //return pointer to previous node

        return _prev;

}





void Node::setData(int *ptr)

{

        //data pointer points to new location

        _data = ptr;

}









int* Node::getData(void)

{

        //return pointer to data location

        return _data;

}









LinkedList::LinkedList()

{

        //initialise node pointers

        _begin = NULL;

        _end = NULL;

        _current = NULL;

}







void LinkedList::addToList(int *data)

{

        Node *newNodePtr;



        //craete new instance of Node

        newNodePtr = new Node;



        //set data

        newNodePtr->setData(data);



        //check if list is empty

        if( _begin == NULL) 

        {

                _begin = newNodePtr;

        }

        else

        {

                newNodePtr->setPrevNode(_end);

                _end->setNextNode(newNodePtr);

        }



        //set current pointer end end pointer

        _end = newNodePtr;

        _current = newNodePtr;

}





int* LinkedList::getCurrent(void)

{

        if(_current != NULL)

        {

                return _current->getData();

        }

        else

        {

                throw exception(NOT_IN_LIST);

        }

}







void LinkedList::deleteCurrent(void)

{

        if(_current != NULL )

        {

                //Warning: something is missing here! Can you see what?!

                _current->getPrevNode()->setNextNode(_current->getNextNode());

                _current->getNextNode()->setPrevNode(_current->getPrevNode());

                

                delete _current;

                _current = NULL;

        }

        else

        {

                throw exception(NOT_IN_LIST);

        }

}





void LinkedList::find(int key)

{

        Node *nodePtr;



        //let pointer point to first element in list

        nodePtr = _begin;



        while(nodePtr != NULL )

        {

                if(*nodePtr->getData()== key)

                {

                        _current = nodePtr;

                        return;

                }

                nodePtr = nodePtr->getNextNode();

        }



        _current = NULL;

        throw exception(NOT_IN_LIST);

}

I've tried changing all the 'int' to 'Vehicle' but as yet have had no joy.

To recap, I'm trying to use this code given to us by our lecturer so that the linked list will contain pointers to objects of the Vehicle class.

Anyone have any ideas?

Oh, and does anyone know what's missing from the deleteCurrent() function?

Thanks in advanced