protocolDemo.m

// Model
// OAStack.m
@protocol OAStack

- (void) pushData:(id)data;
- (id)   popData;

@optional

- (void) purgeStack;

@end

// Model
// OAStackWithArray.m

@implementation OAStackWithArray : NSObject <OAStack>

@property (nonatomic, strong) NSMutableArray *containerArray;
@property (nonatomic, assign) NSUInteger currentIndex;

- (id)init
{
  self = [[super alloc] init];
	if(self){
		self.containerArray = [NSMutableArray array];
		self.currentIndex = 0;
	}
	return self;
}

- (void) pushData:(id)data
{
	self.containerArray[self.currentIndex] = data;
	self.currentIndex++;
}

- (id) popData
{
	NSUInteger idx = self.currentIndex;
	self.currentIndex--;
	self.currentIndex = self.currentIndex < 0 ? 0 : self.currentIndex;
	return self.cointainerArray[idx];
}

@end

// Model
// OAStackHelper.m

@implementation OAStackHelper : NSObject

  def stack
    @stack ||= OAStackWithArray.alloc.inic
  end

  def wrapper_push
    @stack.push.... 
  end

  def wrapper_pop
    @stack.pop .... 
  end


@end

// Controller
// OAStackViewController.m

@implementation OAStackViewController : UIViewController

@property (nonatomic, strong) id<OAStack> stack;

- (void) viewDidLoad
{
	self.stack = [[OAStackHelper alloc] init];
}

- (IBAction) pushDataToStack:(id)sender
{
	UIButton *addButton = (UIButton*)sender;
	[self.stack wrapper_push:addButton.tag];
}

- (IBAction) popDataFromStack:(id)sender
{
	id data = [self.stack wrapper_pop];
}

@end