UIViewController+BackButtonHandler.m

//
//  UIViewController+BackButtonHandler.m
//
//  Created by Sergey Nikitenko on 10/1/13.
//  Copyright 2013 Sergey Nikitenko. All rights reserved.
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.
//

#import "UIViewController+BackButtonHandler.h"
#import <objc/runtime.h>

@implementation UIViewController (BackButtonHandler)

@end

@implementation UINavigationController (ShouldPopOnBackButton)

+ (void)load {
	Method originalMethod = class_getInstanceMethod([self class], @selector(navigationBar:shouldPopItem:));
	Method overloadingMethod = class_getInstanceMethod([self class], @selector(overloaded_navigationBar:shouldPopItem:));
	method_setImplementation(originalMethod, method_getImplementation(overloadingMethod));
}

- (BOOL)overloaded_navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem *)item {

	if([self.viewControllers count] < [navigationBar.items count]) {
		return YES;
	}

	BOOL shouldPop = YES;
	UIViewController* vc = [self topViewController];
	if([vc respondsToSelector:@selector(navigationShouldPopOnBackButton)]) {
		shouldPop = [vc navigationShouldPopOnBackButton];
	}

	if(shouldPop) {
		dispatch_async(dispatch_get_main_queue(), ^{
			[self popViewControllerAnimated:YES];
		});
	} else {
		// Workaround for iOS7.1. Thanks to @boliva - http://stackoverflow.com/posts/comments/34452906
		for(UIView *subview in [navigationBar subviews]) {
			if(0. < subview.alpha && subview.alpha < 1.) {
				[UIView animateWithDuration:.25 animations:^{
					subview.alpha = 1.;
				}];
			}
		}
	}

	return NO;
}

@end