Creating a Stack class

[SamRhoads]

I want to create a class called Stack. I want to be able to add methods like push, pop, and peek. I think such a class would have an NSMutableArray inside, but I don't see why it needs to be a subclass of NSMutableArray. I want to have some additonal special purpose methods in the class. Once created, I want to be able to create several stacks:

Stack stackA;
Stack stackB;

and so on. I then need to be able to push and pop to and from these stacks:

Something *item = [stackA pop];

and I want to be able to assign a current stack to a new stack:

Stack newStack = stackA;

I guess it's clear that I come from a Java background, but I still want to do this. Is there a way to do it? Everything I try crashes.

Thanks,

Sam.

[smasher]

Originally Posted by SamRhoads

I want to create a class called Stack. I want to be able to add methods like push, pop, and peek. I think such a class would have an NSMutableArray inside, but I don't see why it needs to be a subclass of NSMutableArray. I want to have some additonal special purpose methods in the class.

NSMutableArray has an "addObject:" method, which is equivalent to push, and "removeLastObject:" which you could combine with the "lastObject:" method it inherits from NSArray.

You could subclass from NSMutableArray and just add the methods you need; the only reason not to subclass would be to restrict access to the default methods of NSArray and NSMutableArray. But then you'll have to write your own copy methods, etc.

You could also use a "category" to add your custom methods to NSMutableArray without creating a new class, but that might be a bit confusing if you haven't studied it before. Categories let you add methods (but not variables) to existing classes, even system classes.

and I want to be able to assign a current stack to a new stack:

Stack newStack = stackA;

That'll give you two pointers to the same stack. You'll want to use [stackA copy] instead if you need a separate stack.

[SamRhoads]

Sure, I know that.

Originally Posted by smasher

NSMutableArray has an "addObject:" method, which is equivalent to push, and "removeLastObject:" which you could combine with the "lastObject:" method it inherits from NSArray.

You could subclass from NSMutableArray and just add the methods you need; the only reason not to subclass would be to restrict access to the default methods of NSArray and NSMutableArray. But then you'll have to write your own copy methods, etc.

You could also use a "category" to add your custom methods to NSMutableArray without creating a new class, but that might be a bit confusing if you haven't studied it before. Categories let you add methods (but not variables) to existing classes, even system classes.

That'll give you two pointers to the same stack. You'll want to use [stackA copy] instead if you need a separate stack.

I did not try using categories. Maybe that would have done what I wanted.

And I do want two references to the same stack.

Anyway, I finally did create a new class that is NOT a subclass of NSMutableArray, and it behaves JUST like a Stack should. I'll post the code if anyone is interested.

Sam.