SafeNavigationController which instead of ignoring subsequent push calls handles a "push queue"

SafeNavigationController.h

//
//  SafeNavigationController.h
//  SafeNavigationController.h
//
//  Created by 利辺羅 on 2014/08/14.
//  Copyright (c) 2014年 CyberAgent Inc. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface SafeNavigationController : UINavigationController

@end

SafeNavigationController.m

//
//  SafeNavigationController.m
//  SafeNavigationController
//
//  Created by 利辺羅 on 2014/08/14.
//  Copyright (c) 2014年 CyberAgent Inc. All rights reserved.
//

#import "SafeNavigationController.h"

#define timeToWaitBetweenAnimations 0.5

@interface SafeNavigationController ()

@property (nonatomic, strong) NSMutableArray * controllersQueue;
@property (nonatomic)         BOOL animateLastQueuedController;
@property (nonatomic)         BOOL pushScheduled;
@property (nonatomic, strong) NSDate * lastAnimatedPushDate;

@end

@implementation SafeNavigationController

- (void)awakeFromNib
{
    [super awakeFromNib];
    
    self.controllersQueue = [NSMutableArray array];
}

- (void)pushViewController:(UIViewController *)viewController
                  animated:(BOOL)animated
{
    NSLog(@"queue %p", viewController);
    
    [self.controllersQueue addObject:viewController];
    self.animateLastQueuedController = animated;
    
    if (self.pushScheduled)
        return;
    
    // Wait for push animation to finish
    NSTimeInterval timeToWait = self.lastAnimatedPushDate ? timeToWaitBetweenAnimations + [self.lastAnimatedPushDate timeIntervalSinceNow] : 0.0;
    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)((timeToWait > 0.0 ? timeToWait : 0.0) * NSEC_PER_SEC)),
                   dispatch_get_main_queue(), ^
                   {
                       [self pushQueuedControllers];
                       
                       self.lastAnimatedPushDate = self.animateLastQueuedController ? [NSDate date] : nil;
                       self.pushScheduled = NO;
                   });
    self.pushScheduled = YES;
}

- (void)pushQueuedControllers
{
    for (NSInteger index = 0; index < (NSInteger)self.controllersQueue.count - 1; index++)
    {
        NSLog(@"push %p", self.controllersQueue[index]);
        
        [super pushViewController:self.controllersQueue[index]
                         animated:NO];
    }
    
    NSLog(@"push %p animated %@", self.controllersQueue.lastObject, self.animateLastQueuedController ? @"YES" : @"NO");
    
    [super pushViewController:self.controllersQueue.lastObject
                     animated:self.animateLastQueuedController];

    [self.controllersQueue removeAllObjects];
}

@end

怎么用呢？？