Does the iOS SDK provide queues and stacks?

Question

I\'m writing an iPhone app, and I\'m surprised that there seem to be no NSQueue or NSStack classes in Apple\'s Foundation Framework. I see that it would be quite easy to roll m

Answer 1

Another easy way would be to extend NSMutableArray's capabilities by making use of Objective C's categories. You can do that by adding two files to your project:

NSMutableArray+Stack.h

@interface NSMutableArray (StackExtension)

- (void)push:(id)object;
- (id)pop;

@end

NSMutableArray+Stack.m

#import "NSMutableArray+Stack.h"

@implementation NSMutableArray (StackExtension)

- (void)push:(id)object {
    [self addObject:object];
}

- (id)pop {
    id lastObject = [self lastObject];
    [self removeLastObject];
    return lastObject;
}

@end

Now you can use a regular NSMutableArray in every other file of your project like a stack and call push or pop on that object. Don't forget to #import NSMutableArray+Stack.h in those files. Here is some sample code how you can use your new NSMutableArray as a stack:

NSMutableArray *myStack = [[NSMutableArray alloc] init]; // stack size = 0

NSString *aString = @"hello world";
[myStack push:myString];            // stack size = 1

NSString *anotherString = @"hello universe";
[myStack push:anotherString];       // stack size = 2

NSString *topMostStackObject; 

topMostStackObject = [myStack pop]; // stack size = 1
NSLog("%@",topMostStackObject);

topMostStackObject = [myStack pop]; // stack size = 0
NSLog("%@",topMostStackObject);

The log output will be:

hello universe
hello world