How to recognize oneTap/doubleTap at moment?

This is easiest to do without gesture recognizers. Then you can control the delay. The code below is a variation of Apple's original documentation that I use in one of my projects. I have blog post that talks about it as well.

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
 UITouch *touch = [touches anyObject];
if (touch.tapCount == 2) {
//This will cancel the singleTap action
[NSObject cancelPreviousPerformRequestsWithTarget:self];
}

}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{
 UITouch *touch = [touches anyObject];
if (touch.tapCount == 1) {
  //if they tapped within the coin then place the single tap action to fire after a delay of 0.3
  if (CGRectContainsPoint(coin.frame,[touch locationInView:self.view])){
    //this is the single tap action being set on a delay
  [self performSelector:@selector(onFlip) withObject:nil afterDelay:0.3];
  }else{
   //I change the background image here
  }
 } else if (touch.tapCount == 2) {
  //this is the double tap action
  [theCoin changeCoin:coin];
 }
}

Here is a simple custom gesture recognizers for double taps where you can specify the maximum allowed time between taps. This is based on @Walters answer.

PbDoubleTapGestureRecognizer.h :

@interface PbDoubleTapGestureRecognizer : UIGestureRecognizer

@property (nonatomic) NSTimeInterval maximumDoubleTapDuration;

@end

PbDoubleTapGestureRecognizer.m :

#import "PbDoubleTapGestureRecognizer.h"
#import <UIKit/UIGestureRecognizerSubclass.h>

@interface PbDoubleTapGestureRecognizer ()
@property (nonatomic) int tapCount;
@property (nonatomic) NSTimeInterval startTimestamp;
@end

@implementation PbDoubleTapGestureRecognizer

- (id)initWithTarget:(id)target action:(SEL)action {
    self = [super initWithTarget:target action:action];
    if (self) {
        _maximumDoubleTapDuration = 0.3f; // assign default value
    }
    return self;
}

-(void)dealloc {
    [NSObject cancelPreviousPerformRequestsWithTarget:self];
}

- (void)reset {
    [super reset];

    [NSObject cancelPreviousPerformRequestsWithTarget:self];

    self.tapCount = 0;
    self.startTimestamp = 0.f;
}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
    [super touchesBegan:touches withEvent:event];

    if (touches.count != 1 ) {
        self.state = UIGestureRecognizerStateFailed;
    } else {
        if (self.tapCount == 0) {
            self.startTimestamp = event.timestamp;
            [self performSelector:@selector(timeoutMethod) withObject:self afterDelay:self.maximumDoubleTapDuration];
        }
        self.tapCount++;
    }
}

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
    [super touchesMoved:touches withEvent:event];
}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    [super touchesEnded:touches withEvent:event];

    if (self.tapCount > 2) {
        self.state = UIGestureRecognizerStateFailed;
    } else if (self.tapCount == 2 && event.timestamp < self.startTimestamp + self.maximumDoubleTapDuration) {
        [NSObject cancelPreviousPerformRequestsWithTarget:self];
        NSLog(@"Recognized in %f", event.timestamp - self.startTimestamp);
        self.state = UIGestureRecognizerStateRecognized;
    }
}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {
    [super touchesCancelled:touches withEvent:event];
    self.state = UIGestureRecognizerStateFailed;
}

- (void)timeoutMethod {
    self.state = UIGestureRecognizerStateFailed;
}

@end

You can use it like this:

PbDoubleTapGestureRecognizer *doubleTapGr = [[PbDoubleTapGestureRecognizer alloc]initWithTarget:self action:@selector(_doubleTapAction)];
doubleTapGr.maximumDoubleTapDuration = 0.4;
[yourView addGestureRecognizer:doubleTapGr];

You can combine this with requireGestureRecognizerToFail: to get the behavior that was asked for.

The easiest way to do this is to subclass UITapGestureRecognizer and not a general UIGestureRecognizer.

Like this:

#import <UIKit/UIGestureRecognizerSubclass.h>

#define UISHORT_TAP_MAX_DELAY 0.2
@interface UIShortTapGestureRecognizer : UITapGestureRecognizer

@end

And simply implement:

@implementation UIShortTapGestureRecognizer

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
    [super touchesBegan:touches withEvent:event];
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(UISHORT_TAP_MAX_DELAY * NSEC_PER_SEC)), dispatch_get_main_queue(), ^
    {
        // Enough time has passed and the gesture was not recognized -> It has failed.
        if  (self.state != UIGestureRecognizerStateRecognized)
        {
            self.state = UIGestureRecognizerStateFailed;
        }
    });
}
@end

only thing you need to do is add extra line of code to use requireGestureRecognizerToFail

[singleTapRecognizer requireGestureRecognizerToFail:doubleTapRecognizer];

then whole code become to:

UITapGestureRecognizer *doubleTapRecognizer = [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(beginComicTransitions:)] autorelease];    
doubleTapRecognizer.numberOfTapsRequired = 2;
doubleTapRecognizer.numberOfTouchesRequired = 1;
doubleTapRecognizer.delegate = self;   

UITapGestureRecognizer *singleTapRecognizer = [[[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(bringMenu:)] autorelease];    
singleTapRecognizer.numberOfTapsRequired = 1;
singleTapRecognizer.numberOfTouchesRequired = 1;
singleTapRecognizer.delegate = self;

[singleTapRecognizer requireGestureRecognizerToFail:doubleTapRecognizer];

here's requireGestureRecognizerToFail means:

• if not recognized double tap, then single tap be recognized
• if recognized double tap, will not recognize single tap

swift version code is:

    let doubleTap = UITapGestureRecognizer(target: self, action: "doubleTapped:")
    doubleTap.numberOfTapsRequired = 2
    doubleTap.numberOfTouchesRequired = 1
    self.scrollView.addGestureRecognizer(doubleTap)

    let singleTap = UITapGestureRecognizer(target: self, action: "singleTap:")
    singleTap.numberOfTapsRequired = 1
    singleTap.numberOfTouchesRequired = 1
    self.scrollView.addGestureRecognizer(singleTap)

    singleTap.requireGestureRecognizerToFail(doubleTap)