Thread: Pointer problem

Hi Im having a few problems with pointers and was wondering whether anyone can point me in the right direction.

I have the following code:

Code:

class LatticeNode {

	public:
		int num;
		Cell c;

		LatticeNode *next;
		LatticeNode *prev;
	
		Cell* getCell() { return c; }
		LatticeNode(Cell *c);
};

This forms part of a larger class which forms a simple linked list:

Code:

template< class T, int size> class Lattice 
{
	public:

		Lattice();
		~Lattice();

		LatticeNode *getCurrent() { return current; }

		void polarise();

	private:

		LatticeNode* current;
};

Now im trying to use the getCell method from LatticeNode to return the object Cell c from the LatticeNode object, like so:

Code:

current->getCell()->signal(dt);

Where signal(dt) is a function in the object Cell. If i call it like this then it crashes, and i dont understand why its causing this..

Im not sure on the return type for the getCell function .. do i return just c or a reference to &c?

I believe the Cell object is being created when i call the LatticeNode constructor, although am i pointing to something which doesnt exist??

Any help, suggestions welcomed!

Originally Posted by ventolin

Code:

class LatticeNode {

	public:
		int num;
		Cell c;

		LatticeNode *next;
		LatticeNode *prev;
	
		Cell* getCell() { return c; }
		LatticeNode(Cell *c);
};

You are saying getCell returns a pointer to a cell but you are trying to return the cell itself. Possible changes:

Code:

Cell& getCell { return c; }
Cell* getCell { return &c; }

Now the top one returns a reference to the cell so you would

Code:

current->getCell().signal(dt);

With the bottom one it returns a pointer so you wouldn't need to change it. I'm surprised your compiler didn't warn about this though.

Is there no way to do it without using a reference to the object? or can i still use the pointer method? If i use the reference style i need to major changes to all of my code... and my compiler (VC++) complains if i have the two methods...

No you can use the pointer method. Was just giving you options

Ok thanks ill take a look at this.. cheers!