BPNavigationController.h

//
//  BPNavigationController.h
//  StatusBarSize
//
//  Created by Anders Borch on 10/16/11.
//  Copyright (c) 2011 Bump. All rights reserved.
//

#import <UIKit/UIKit.h>

@interface BPNavigationController : UINavigationController

/*!
 @method setup
 @abstract Setup UINavigationController to handle non-fullscreen modals.
 @discussion
 This will replace the implementation of presentModalViewController:animated: with a new implementation 
 which retains the original frame of the UINavigationController#view and pushes a 
 */
+ (void)setup;

@end

BPNavigationController.m

//
//  BPNavigationController.m
//  StatusBarSize
//
//  Created by Anders Borch on 10/16/11.
//  Copyright (c) 2011 Bump. All rights reserved.
//

#import "BPNavigationController.h"
#import <objc/runtime.h>

@interface UINavigationController (BPNavigationController)
- (void)_bp_presentModalViewController:(UIViewController*)controller animated:(BOOL)animated;
- (void)_bp_dismissModalViewControllerAnimated:(BOOL)animated;
@end

#pragma mark - Helper

@interface BPNavigationControllerInvocationHelper : NSObject {
    UIViewController *_controller;
    CGRect _frame;
    id<UINavigationControllerDelegate> _delegate;
}
@property (nonatomic,retain) UIViewController *controller;
@property (nonatomic,assign) CGRect frame;
@property (nonatomic,retain) id<UINavigationControllerDelegate> delegate;
@end
@implementation BPNavigationControllerInvocationHelper
@synthesize controller=_controller, frame=_frame, delegate=_delegate;
- (void)dealloc
{
    self.controller = nil;
    self.delegate = nil;
    [super dealloc];
}
@end

#pragma mark - Replacement definitions

void present_helper(UINavigationController *self, SEL _cmd, BPNavigationControllerInvocationHelper *helper);
void present(UINavigationController *self, SEL _cmd, UIViewController *controller, BOOL animated);
void dismiss(UINavigationController *self, SEL _cmd, BOOL animated);

#pragma mark - Replacement implementations

void present_helper(UINavigationController *self, SEL _cmd, BPNavigationControllerInvocationHelper *helper)
{
    // reset the frame
    self.view.frame = helper.frame;
    helper.controller.view.frame = helper.frame;
    // notify delegate of completion
    [helper.delegate navigationController: self
	            didShowViewController: helper.controller
			         animated: YES];
	self.delegate = helper.delegate;
}

void present(UINavigationController *self, SEL _cmd, UIViewController *controller, BOOL animated)
{
    CGRect rect = [self.view frame];
    
    controller.view.frame = CGRectOffset(rect, 0.0f, rect.size.height);
    [self.view addSubview: controller.view];
    
    BPNavigationControllerInvocationHelper *helper = [[BPNavigationControllerInvocationHelper alloc] init];
    helper.controller = controller;
    helper.frame = rect;

    if (animated) {
        // manual notification of delegate
	helper.delegate = self.delegate;
	self.delegate = nil;
	[helper.delegate navigationController: self
	               willShowViewController: controller
				     animated: YES];
		
        [UIView animateWithDuration: 0.3
                              delay: 0.0
                            options: UIViewAnimationCurveEaseOut 
                         animations: ^{
                             helper.controller.view.frame = self.view.bounds;
                         }
                         completion: ^(BOOL finished) {
			     // call the *original* method
			     [self _bp_presentModalViewController: controller
				 		         animated: NO];
                             if (finished) {
                                 // reset the frame and notify delegate
                                 [self performSelector: @selector(_bp_presentModalViewControllerWithHelper:) 
                                            withObject: helper
                                            afterDelay: 0.0];
                             }

			     [helper release];
			 }];
    } else {
        // call the *original* method
        [self _bp_presentModalViewController: controller
                                    animated: NO];

        // reset the frame
        [self performSelector: @selector(_bp_presentModalViewControllerWithHelper:) 
                   withObject: helper
                   afterDelay: 0.0];
        [helper release];
    }
}

void dismiss(UINavigationController *self, SEL _cmd, BOOL animated)
{
    CGRect rect = [self.view frame];

    UIViewController *controller = [self.modalViewController retain];

	id<UINavigationControllerDelegate> _delegate = self.delegate;
	if (animated) {
		// manual notification of delegate
		self.delegate = nil;
		[_delegate navigationController: self
		         willShowViewController: self.topViewController
			 	       animated: YES];
	}

    // call the *original* method
    [self _bp_dismissModalViewControllerAnimated: NO];
    
    // reset the navigation frame
    self.view.frame = rect;

    if (animated) {
        [self.view addSubview: controller.view];
        controller.view.frame = self.view.bounds;
        
        [UIView animateWithDuration: 0.3
                              delay: 0.0
                            options: UIViewAnimationCurveEaseIn
                         animations: ^{
                             controller.view.frame = CGRectOffset(rect, 0.0f, rect.size.height);
                         }
                         completion: ^(BOOL finished) {
                             [controller.view removeFromSuperview];
                             [controller release];
							 
	  		     // manual notification of delegate
			     [_delegate navigationController: self
				       didShowViewController: self.topViewController
					            animated: YES];
			     self.delegate = _delegate;
                         }];
    } else {
        [controller release];
    }
}

#pragma mark -

@implementation BPNavigationController

+ (void)setup {
    class_addMethod([UINavigationController class], 
                    @selector(_bp_presentModalViewController:animated:), 
                    (IMP)present, 
                    "v@:@c");
    class_addMethod([UINavigationController class], 
                    @selector(_bp_presentModalViewControllerWithHelper:), 
                    (IMP)present_helper, 
                    "v@:@");
    class_addMethod([UINavigationController class], 
                    @selector(_bp_dismissModalViewControllerAnimated:), 
                    (IMP)dismiss, 
                    "v@:c");

    // replace present modal
    Method orig_method = nil, alt_method = nil;
    orig_method = class_getInstanceMethod([UINavigationController class], 
                                          @selector(presentModalViewController:animated:));
    alt_method = class_getInstanceMethod([UINavigationController class], 
                                         @selector(_bp_presentModalViewController:animated:));
    method_exchangeImplementations(orig_method, alt_method);

    // replace dismiss modal
    orig_method = class_getInstanceMethod([UINavigationController class], 
                                          @selector(dismissModalViewControllerAnimated:));
    alt_method = class_getInstanceMethod([UINavigationController class], 
                                         @selector(_bp_dismissModalViewControllerAnimated:));
    method_exchangeImplementations(orig_method, alt_method);

}

@end