Flatiron School Week 4- Hacking together the TinderClone Swipe Feature

The Tinder Swipe

The central part of Tinder’s design is the swiping mechanism. The feature allows people to focus on one match at a time and make a decision before moving on to the next match.  Good for spending more time on matches and good for reducing the speed of data consumption.

I wanted to learn about animations, so this weekend I hacked together a prototype of the feature.


All the code can be found here along with a video demo. The code is very dirty, but that’s topic for another week.


Step 1. Look up how to do it.

The next step in my TinderClone project is to make the swipeable images. Richard Kim has a really cool blog entry about how to make this feature three different ways. Since I’m taking on this project to learn to code, I took the “build it from scratch” way and tried to follow Nimrod Gutman’s blog. I totally failed. Twice.

It turns out that I didn’t really understand how UIView and UIImageViews worked. So, I decided to play around with them.

Step 2. Read up on UIViews

I read thought through the Apple View Programming Guide. in particular, the view and window architecture. I didn’t really understand bounds very well, so I started an Xcode project called playingWithBounds, that ended up being my project.


  • Views are made on top of Core Animation layers (CALayer). Views have animation, but go to CALayer to one layer deeper for more control.
  • Subviews are arranged in an array in the superview.
  • UIContentMode is useful for sizing images. I played around with this later.
  • I thought the bounds property might have something to do with Box Sizing in CSS, but it’s much simpler. The bounds change the frame of the box.

UIView properties

  • frame- used for making objects. CGRectMake()
  • bounds- changes the size of the view, but not the center.
  • center- very important for moving objects around.
  • transform- used to rotate, move and scale objects. It’s the finishing touch. The object is drawn and then transformed. When an object is rotated, it remembers what it’s heigh and width were when it wasn’t rotated.
  • alpha- 1 is opaque and 0 is fully transparent. Great for
  • backgroundColor- useful for seeing where the rectangle is.

Step 3. Playing around with the UIView properties

I made single view project where I drew boxes and changed the bounds, and so on to see what would happen.

Step 4. Playing around with CGAffineTranform

When I got to Coordinate System Transformations, I started playing around with rotating and moving boxes.

I made a slider to rotate an UIImageView.

        CGRect slideFrame = CGRectMake(100, 400, 200, 20);
        self.pictureRotationAngle = [[UISlider alloc] initWithFrame:slideFrame];
        [self.view addSubview:self.pictureRotationAngle];
        self.pictureRotationAngle.minimumValue = 0;
        self.pictureRotationAngle.maximumValue = 2*M_PI;
        self.pictureRotationAngle.value = M_PI/2.0;
        [self.pictureRotationAngle addTarget:self action:@selector(rotateImage) forControlEvents:UIControlEventValueChanged];
        self.picture.transform = CGAffineTransformMakeRotation(self.pictureRotationAngle.value);

Step 5. Finding the Event Handling methods

Where other solutions mentioned at the top used UIGestureRecognizers, I imagined that these event handling methods could move my picture around too. They used UITouch objects.

I was touching my UIImageView and nothing was happening. Googling around, I found that UIImageViews are not user interactive by default. So, I had to set it.

    self.picture.userInteractionEnabled = YES;

I also set the

What is UITouch?

I didn’t know, so I built the first three methods and NSLogged the touch and event objects. They were very descriptive.

2014-10-27 18:58:26.919 TinderSwipeFeature[65292:2410541] <UITouch: 0x7fdf015533a0> phase: Moved tap count: 1 window: <UIWindow: 0x7fdf01409040; frame = (0 0; 375 667); gestureRecognizers = <NSArray: 0x7fdf01403730>; layer = <UIWindowLayer: 0x7fdf01414c50>> view: <UIImageView: 0x7fdf01684780; frame = (37.8671 64.9702; 402.124 402.124); transform = [0.99420459268393058, -0.10750454821160646, 0.10750454821160646, 0.99420459268393058, 0, 0]; clipsToBounds = YES; opaque = NO; layer = <CALayer: 0x7fdf01684ac0>> location in window: {256, 332} previous location in window: {255, 332} location in view: {192.38019379786252, 249.92073845470227} previous location in view: {191.38598920517859, 249.81323390649064}

UITouch has a lot of really useful info:

  • Size of the screen: 375 width and 667 points height.
    frame = (0 0; 375 667)
  • The view touched and it’s location
    view: <UIImageView: 0x7fdf01684780; frame = (37.8671 64.9702; 402.124 402.124)
  • Current touch location in view and window
    location in window: {256, 332} 
    location in view: {192.38019379786252, 249.92073845470227}
  • Previous touch location in view and window
    previous location in window: {255, 332}
    previous location in view: {191.38598920517859, 249.81323390649064}
  • Timestamp
    2014-10-27 18:58:26.919

I now had the velocity of touches and I just needed to update the view being touched with a new center value to move it.

That was the key to solving the problem.

I added the other Tinder style animations associated with swiping. All of these were based on using the x location of the touch divided by the width of the phone to calculate a factor that would modify the rotation of the image and the opacity of the overlaps.

Step 6. Playing with contentMode

When I put the picture in the UIImageView, it would not fit in the frame, so I had to set clipsToBounds to YES and change the contentMode from UIViewContentModeScaleToFill to UIViewContentModeScaleAspectFill. UIViewContentModeScaleAspectFit also works but you get white space on the sides.

    self.picture.contentMode = UIViewContentModeScaleAspectFill;
    self.picture.clipsToBounds = YES;

The other options such as UIViewContentModeTop maintain the size of the image, and align the listed edge to the corresponding edge in the box. For example,

  • UIViewContentModeTop aligns the image to the top of the UIImageView.
  • UIViewContentModeTopLeft aligns the image to the top and left of the UIImageView.

Step 7. Animation timing

For the touchesEnded method, I wanted to animate the image moving back into location.

[UIView animateWithDuration:0.4 delay:0 usingSpringWithDamping:0.6 initialSpringVelocity:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
                ... reset image
            } completion:nil];

CGAffineTransformIdentity removes all transforms (rotations, scaling, translations).

Step 8. Animation for the picture flying off the screen or springing back

To animate the picture flying off to the side, I set a swipe threshold of 30% of the width.

if (differenceInTouchLocationX > aTouch.window.frame.size.width*0.2) {
            [UIView animateWithDuration:0.5 animations:^{
                viewTouched.center = CGPointMake(self.view.frame.size.width*2, currentLocation.y + 0.5 * speedY) ;
            NSLog(@"%@", aTouch);
        }else if (differenceInTouchLocationX < -aTouch.window.frame.size.width*0.3)
            [UIView animateWithDuration:0.5 animations:^{
                viewTouched.center = CGPointMake(-self.view.frame.size.width*2, currentLocation.y + 0.5 * speedY) ;
        else { 
             ... //springs back to original location

Step 9. Add the overlap images (Like and Nope)

self.like = [[UILabel alloc] initWithFrame:CGRectMake(20, 20, 100, 50)];
 [self.like setFont:[UIFont systemFontOfSize:100]];
 self.like.text = @"L I K E";
 self.like.adjustsFontSizeToFitWidth = YES;
 [self.like setBaselineAdjustment:UIBaselineAdjustmentAlignCenters];
 [self.like setTextColor:[UIColor colorWithRed:47/255.0f green:156/255.0f blue:28/255.0f alpha:1]];
// self.like.backgroundColor = [UIColor blueColor];
 self.like.transform = CGAffineTransformMakeRotation(-20* M_PI/180);
 self.like.alpha = 0;

Boy, I learned a lot by just reading the documentation and Googling. That was fun!

Week 2- Tinder Clone. Breaking down into Objects. Setting up the PageViewController

I felt that I had enough knowledge to start building apps so I decided to copy some popular apps with interesting mechanisms. The idea is to do one every week or two, so that I can build a lot of these apps and learn how they are built.

Why build lots of apps?

Part of my inspiration has been Ira Glass’s notes on storytelling where he walks about beginners needing to do a great volume of work before they can make things that they think are good enough. I’m starting that journey now.

Why reverse engineer apps and not build original apps?

When artists learn to paint, they copy other artists to learn how something is done. In app making, I’m doing the same by analyzing and appreciating how other developers have made their apps.

Project 1 is Tinder.

The interesting mechanism here is the swipe left or right to like or dislike.

Step 1 Break down the app into views

Sketch of Tinder Settings Page
Sketch of Tinder Settings Page
Sketch of Tinder Match Page
Sketch of Tinder Match Page
Sketch of Tinder Messages Page
Sketch of Tinder Messages Page

For my first iteration, I really just want the settings and the match page to work. The messages would be part of the second iteration and moments would be part of the third.

Step 2. Take the views and make the data model

I started by translating the Settings and Match views into classes and properties, leaving the methods fluid for now.

There needs to be a Person class.

Person Class
Person Class

The Facebook properties would be imported with Facebook authentication and the rest would be set by the customer.

For simplicity, I have the location as a NSString now.

When I thought about how the custom initializer would work, I realized that I would probably need to split this class up into small modules with Discovery Properties, and Facebook Properties as classes.

I realized that I would also need a way to match people. It made more sense to make a Matcher class because I would want a central place to store data and review the results (whether people liked each other) to see how well my matching algorithm was working.

MatchMaker Class
MatchMaker Class

Naturally, the array of matches would need a match object, so I wrote a match class.

Match Class
Match Class

Step 3. Make the basic interface in storyboard

Tinder has four pages but I just wanted to mock up the Settings, Match and Messages pages.


  • Slides horizontally from page to page with Settings, Match, and Messages page from left to right.
  • Starts on the Match Page

1st Iteration

Test: I tried three UIViewControllers with buttons on navigation bars that went between the three pages.

  1. Select the storyboard or make one (File > New > File Cmd-N, iOS > User Interface > Storyboard)
  2. Add three View Controllers from the bottom of the Utilities column (right sidebar).
  3. Add a navigation bar to each of the three view controllers.
  4. Add bar button items to each screen as shown below.
  5. Add segues for the bar buttons to the adjacent screens.
1st Iteration of the Storyboard
1st Iteration of the Storyboard

Results: As I found out after running this, the transitions make the new screen pop up from the bottom like a modal window.

  • Slides horizontally from page to page with Settings, Match, and Messages page from left to right. 
  • Starts on the Match Page

2nd Iteration

Test: Use a navigation controller.

I have a navigation controller with the root controller as the Settings page with the Match page and the Messages Page linked to that.

2nd Iteration of the Storyboard
2nd Iteration of the Storyboard using a Navigation Controller

Results: The transitions are now horizontal between pages. It’s not smooth like Tinder’s touch gestures, but it’s close. The app doesn’t start on the match page though if I want the sliding to work in this order.

  • Slides horizontally from page to page with Settings, Match, and Messages page from left to right. 
  • Starts on the Match Page

3rd Iteration

Test: Make the Match page the root view controller and add a link back to the settings page.

3rd Iteration of the Storyboard
3rd Iteration of the Storyboard

Results: After clicking the settings button, the transition slid from right to left and the Settings pages looks just like the messages page. Not what I wanted.

  • Slides horizontally from page to page with Settings, Match, and Messages page from left to right. 
  • Starts on the Match Page

4th Iteration

Test: I’m guessing that the transition is either a customer segue or there’s something about gestures that I don’t know. I’m going to look into gestures between views.

As I looked through the gestures, I noticed the Page View Controller. After googling it and finding this AppCoda tutorial,  the scroll transition looks exactly like what Tinder uses.

5th Iteration

A Page View Controller is a container controller that you put other view controllers inside.

So, I’m going to need to make three classes of view controllers that show the Settings, Match and Messages pages. Then, I’ll put them inside the page view controller.

Looking through the PageViewDemo from the AppCoda tutorial, I see that they have one view controller that creates a pageViewController, provides the data for the pageViewController and sets an array of PageContentViewControllers in the pageViewController.

Sidebar: Navigation Bar vs. Navigation Item

When I was using the Navigation Controller, I needed to add navigation items to the Settings, Match and Message view controllers to be able to add a title to each slide.

When I deleted the Navigation Controller, I made the navigation bar disappear. While the navigation item was still there, it was useless without the navigation bar, so I had to add three navigation bars onto the Settings, Match and Message view controllers.

Where a navigation controller exists, add navigation items. Where there is not , add navigation bars. 

Test: In order to implement the pageViewController, I added a ViewController class inheriting from UIViewController and added a PageViewController, a SettingsViewController, MatchViewController, and MessagesViewController into the properties. The last three are custom classes inheriting from UIViewController.

ViewController.h inheriting from UIViewController
ViewController.m inheriting from UIViewController

I created the five view controllers in the Storyboard and added their class name to each corresponding storyboard ID.

5th iteration of the storyboard
5th iteration of the storyboard

Then I set the properties in ViewController.m to each of the storyboard IDs.


Here I set the match view controller to be the starting one.

  • Slides horizontally from page to page with Settings, Match, and Messages page from left to right. 
  • Starts on the Match Page

Now it starts with the match page, but doesn’t have any other other pages. The Settings and Messages pages are there, but they are not connected yet.

I see that the PageViewDemo has two methods called

- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController *)viewController


- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController *)viewController

That’s probably what I want to tell the page view controller how to switch between the Settings, Match and Messages view controllers.

When I try to type those in, they were not autocompleting, which means that I was missing something. I think it’s because I haven’t set the ViewController to follow the pageViewControllerDataSource Protocol. After I add that to the ViewController.h file. I get a warning. Yes!!

PageViewControllerDataSource Protocol Warning
PageViewControllerDataSource Protocol Warning

Now I understand why the PageViewDemo had

    self.pageViewController.dataSource = self;

in the viewDidLoad.

Since I only had three pages, I wrote two simple if statement for the viewControllerBefore and viewControllerAfter methods and everything works.

  • Slides horizontally from page to page with Settings, Match, and Messages page from left to right. 
  • Starts on the Match Page