/*

     File: ViewController.m 

 Abstract: The view controller used for transitioning between two UIViews. 

  Version: 1.12 

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 */

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, strong) IBOutlet UIImageView *frontView;

@property (nonatomic, strong) IBOutlet UIImageView *backView;

@property (nonatomic, weak) IBOutlet UIBarButtonItem *fadeButton;

@property (nonatomic, weak) IBOutlet UIBarButtonItem *flipButton;

@property (nonatomic, weak) IBOutlet UIBarButtonItem *bounceButton;

@property (nonatomic, strong) NSArray *priorConstraints;

- (IBAction)flipAction:(id)sender;

- (IBAction)fadeAction:(id)sender;

- (IBAction)bounceAction:(id)sender;

@end

#pragma mark -

@implementation ViewController

// makes "subview" match the width and height of "superview" by adding the proper auto layout constraints

//

- (NSArray *)constrainSubview:(UIView *)subview toMatchWithSuperview:(UIView *)superview

{

    subview.translatesAutoresizingMaskIntoConstraints = NO;

    NSDictionary *viewsDictionary = NSDictionaryOfVariableBindings(subview);

    NSArray *constraints = [NSLayoutConstraint

                            constraintsWithVisualFormat:@"H:|[subview]|"

                            options:0

                            metrics:nil

                            views:viewsDictionary];

    constraints = [constraints arrayByAddingObjectsFromArray:

                   [NSLayoutConstraint

                    constraintsWithVisualFormat:@"V:|[subview]|"

                    options:0

                    metrics:nil

                    views:viewsDictionary]];

    [superview addConstraints:constraints];

    return constraints;

}

- (void)viewDidLoad

{

    [super viewDidLoad];

    // start off by using the front view (Palm trees)

    [self.view addSubview:self.frontView];

    // since frontView has no constraints set to match it's superview, we set them here

    _priorConstraints = [self constrainSubview:self.frontView toMatchWithSuperview:self.view];

    // configure our toolbar with the appropriate transition effects

    // note: the bounce button only shows for iOS 7.0 or later

    //

    UIBarButtonItem *flexItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil];

    NSMutableArray *toolbarButtons = [NSMutableArray arrayWithObjects:flexItem, self.fadeButton, self.flipButton, nil];

    if ([[UIView class] respondsToSelector:

         @selector(animateWithDuration:delay:usingSpringWithDamping:initialSpringVelocity:options:animations:completion:)])

    {

        [toolbarButtons addObject:self.bounceButton];

    }

    [toolbarButtons addObject:flexItem];

    self.toolbarItems = toolbarButtons;

}

- (void)performTransition:(UIViewAnimationOptions)options

{

    UIView *fromView, *toView;

    if ([self.frontView superview] != nil)

    {

        fromView = self.frontView;

        toView = self.backView;

    }

    else

    {

        fromView = self.backView;

        toView = self.frontView;

    }

    NSArray *priorConstraints = self.priorConstraints;

    [UIView transitionFromView:fromView

                        toView:toView

                      duration:1.0

                       options:options

                    completion:^(BOOL finished) {

                        // animation completed

                        if (priorConstraints != nil)

                        {

                            [self.view removeConstraints:priorConstraints];

                        }

                    }];

    _priorConstraints = [self constrainSubview:toView toMatchWithSuperview:self.view];

}

#pragma mark - Actions

- (IBAction)fadeAction:(id)sender

{

    [self performTransition:UIViewAnimationOptionTransitionCrossDissolve];

}

- (IBAction)flipAction:(id)sender

{

    UIViewAnimationOptions transitionOptions = ([self.frontView superview] != nil) ?

    UIViewAnimationOptionTransitionFlipFromLeft : UIViewAnimationOptionTransitionFlipFromRight;

    [self performTransition:transitionOptions];

}

- (IBAction)bounceAction:(id)sender

{

    if ([[UIView class] respondsToSelector:

         @selector(animateWithDuration:delay:usingSpringWithDamping:initialSpringVelocity:options:animations:completion:)])

    {

        // no other transitions are allowed until this one finishes

        self.navigationController.toolbar.userInteractionEnabled = NO;

        UIView *fromView, *toView;

        if ([self.frontView superview] != nil)

        {

            fromView = self.frontView;

            toView = self.backView;

        }

        else

        {

            fromView = self.backView;

            toView = self.frontView;

        }

        CGRect startFrame = self.view.frame;

        CGRect endFrame = self.view.frame;

        // the start position is below the bottom of the visible frame

        startFrame.origin.y = -startFrame.size.height;

        endFrame.origin.y = 0;

        toView.frame = startFrame;

        NSArray *priorConstraints = self.priorConstraints;

        [self.view addSubview:toView];

        [UIView animateWithDuration:1.0f

                              delay:0.0

             usingSpringWithDamping:0.5

              initialSpringVelocity:5.0

                            options:0

                         animations:^{ toView.frame = endFrame; }

                         completion:^(BOOL finished) {

                             // slide down animation finished, remove the older view and the constraints

                             //

                             if (priorConstraints != nil)

                                 [self.view removeConstraints:priorConstraints];

                             [fromView removeFromSuperview];

                             self.navigationController.toolbar.userInteractionEnabled = YES;

                         }];

        // apply the new constraints to our newly added subview

        _priorConstraints = [self constrainSubview:toView toMatchWithSuperview:self.view];

    }

}

@end