How can I programmatically pause an NSTimer?

Question

I\'m using an NSTimer to do some rendering in an OpenGL based iPhone app. I have a modal dialog box that pops up and requests user input. While the user is providing input

Answer 1

Based off @Thiru and @kapesoftware's answers, I made an Objective-C category on NSTimer using Associated Objects for pausing and resuming the timer.

#import 

@interface NSTimer (PausableTimer)

@property (nonatomic, retain) NSDate *pausedDate;

@property (nonatomic, retain) NSDate *nextFireDate;

-(void)pause;

-(void)resume;

@end

...

@implementation NSTimer (PausableTimer)

static char * kPausedDate = "pausedDate";
static char * kNextFireDate = "nextFireDate";

@dynamic pausedDate;
@dynamic nextFireDate;

-(void)pause {

  self.pausedDate = [NSDate date];

  self.nextFireDate = [self fireDate];

  [self setFireDate:[NSDate distantFuture]];
}

-(void)resume
{
  float pauseTime = -1*[self.pausedDate timeIntervalSinceNow];

  [self setFireDate:[self.nextFireDate initWithTimeInterval:pauseTime sinceDate:self.nextFireDate]];
}

- (void)setPausedDate:(NSDate *)pausedDate
{
  objc_setAssociatedObject(self, kPausedDate, pausedDate, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (NSDate *)pausedDate
{
  return objc_getAssociatedObject(self, kPausedDate);
}

- (void)setNextFireDate:(NSDate *)nextFireDate
{
  objc_setAssociatedObject(self, kNextFireDate, nextFireDate, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (NSDate *)nextFireDate
{
  return objc_getAssociatedObject(self, kNextFireDate);
}

It keeps things tidy and means you don't have to create instance variables or properties just to pause and resume your timers.