Parallax UITableView header with Auto Layout

I’ve been working on a thing at Shopify, where I implemented a header containing an image that has a parallax effect when scrolling up and expands when scrolling down.

This isn’t exactly a new thing, but I wanted to implement it using Auto Layout and couldn’t find any examples of this. It turns out it’s super simple, so I found some time tonight and created a demo project you can find the code on Github:

Parallax Auto Layout Demo

To achieve the effect, you simply add the image view inside a container view that gets clipped bounds. Using two NSLayoutContraints, you then set the height of the container view and the height of the image view.

A bit more work is required if you’re working with portrait and landscape images, but the effect is very simple to achieve.

Preventing iTunes Preview glossy app icon

I recently posted a question on Twitter that was left unanswered.

Multiple online searches also left me without a solution, so I decided to test a possible solution with a new update for an app in the App Store and it turns out I found the answer.

The problem I had can be seen with the Facebook app icon on iTunes Preview on the web:


The Facebook app icon on the iTunes Preview on the web shows the app icon with a glossy overlay, a trend that’s pretty much gone with iOS 7 – and I don’t recall the Facebook app icon having a glossy overlay for years either. If you look at the app in the iTunes App Store or on the App Store on your device it does not have a glossy overlay. Furthermore, the rounding of the icon is also different than App Store previews elsewhere (though my glossy-solution won’t solve that issue).

With Xcode 5 I had moved over to using Image Assets which lets you manage all images for app, including icons used in the app for example, as well as app Launch Images and App Icons:


With Image Assets you can supply various app icon sizes and you do not have to specify them in the app’s .plist and you are also able to specify whether an app icon is pre-rendered (telling Apple not to add a glossy effect for pre-iOS 7 apps). This setting does in fact ensure that you app icon won’t be rendered with a glossy icon on the App Store in iTunes and on devices, but it does not ensure that your app icon won’t have it on iTunes Preview on the web!

In order to get rid of the glossy effect on your app icon, you will have to re-add the


flag in your app’s .plist and set it to TRUE<. In Xcode this is converted to

Icon already includes gloss effects

and should be set to YES:


Once you add this flag to your app’s .plist the app icon in iTunes Preview on the web will new render without a glossy overlay! Tada!


Xcode code snippets and syncing

Earlier today I took some time to create a few more code snippets in Xcode for code I’ve been writing a lot of lately. I’ve never really seen or discussed these much with other developers, so I was wondering whether people actually use them – and to what extent? I know from my own experience that I don’t use them nearly enough, so I thought I’d write up a quick post on Xcode’s awesome Code Snippet Library.

The Code Snippet Library in Xcode is a great feature and a huge time saver – you’ll be doing yourself a favour by using it if you haven’t already! Ever noticed how when you start typing “init” Xcode will autosuggest the Objective-C init method? It does this because it’s a code snippet with a completion shortcut “init”. Same with “forin”, “dealloc” and many more built-in code snippets. Check each snippet’s completion shortcut in their edit mode.

Objective-C init method code snippet

Here’s a basic example of a “user” code snippet I have in my library:

UIAlertView boilerplate code snippet

I wrote up the code for a UIAlertView, highlighted the code and dragged it into the Code Snippet Library. The code snippet retains the parameter placeholders as well as your indentation (don’t worry about the indentation in the preview box such as in the example above, as long as it’s correct when used in your code). Now for the awesome part: Notice how I set the Completion Shortcut to “alertview” and the Completion Scope to “Code Expression”? Now, if I type alertview inside a method Xcode will auto-suggest this entire code snippet and I simple hit enter to use it and tab through the parameters to quickly setup a UIAlertView. Thanks Xcode <3

The Completion Scope is fairly important as it allows you to set the scope for when Xcode should auto-suggest your code snippet. If a code snippet is a method, set the scope as such and Xcode won’t auto-suggest that snippet if you’re inside a method. If you’re writing code for both OS X and iOS you can also set a specific platform for the code snippet so you’re not having your UIKit-specific code snippets suggested when you’re writing code for a Mac app.

Keeping your Code Snippet Library in sync

An hour ago, I tweeted about syncing Xcode Code Snippet Library with Xcode, which basically led me to writing up this blog post.

I’ve got my Macbook Pro at work and Mac Pro at home and often switch between the two. Unfortunately Xcode doesn’t have iCloud syncing – though what a nice feature this would be – so keeping your Code Snippet Library in sync could be a small pain. Enter symlinks.

Custom code snippets can be found in


Each code snippet is a plist file, which means adding or deleting code snippets on any machines won’t give you any issues (I believe it would in Xcode 3 because all snippets were saved into one file, which may have created some conflicts depending on the method used to sync).

Assuming you’re a Dropbox user*, you can use it to sync user Code Snippets between two or more machines. In the following example, I’ve setup a folder in Dropbox for Xcode. I’ll move my /CodeSnippet folder to the Xcode folder in Dropbox and setup a symlink in the original path that points to the CodeSnippet folder in my Dropbox:

$ cd ~/Library/Developer/Xcode/UserData
$ mv CodeSnippets /Dropbox/Xcode/
$ ln -s ~/Dropbox/Xcode/CodeSnippets/ CodeSnippets

You may have to sudo the last line, but now you should be all set. Do the same thing on your other machine(s) and start creating lots of useful snippets to use on any machine you’re working on! Don’t forget Completion Shortcuts to make your life much easier.

Hope you found this post useful. If you have similar tips, feel free to share in the comments. @tewha replied to my tweet saying that he uses symlinks to sync Archived builds and other Xcode User Data across several machines.

*If you’re not a Dropbox user, feel free to use my referral link :)

Core Location presentation at TACOW

Last night, I did a presentation on Core Location for TACOW’s (Toronto Area Cocoa and WebObjects developers group) quarterly meet-up. I volunteered during a lunch with the group’s co-founders David (@rebeld) and Karl (@kolpanic) on the last day of WWDC.

I picked Core Location since I had learned some good insight at WWDC and also worked with the framework thoroughly through building my app Next TTC.

The presentation went well and was well-received, and I am now posting it here for everyone else to enjoy. I have left my notes in the presentation, but I am not sure how much help that will be. I suggest you view the presentation in Play mode, just so the animations help understand the content a bit better.

Download: Core Location Keynote presentation


Random tips

I was expecting this blog post to be about something completely different, but I’m still out of the country and have come down with a bad cold, so it’ll be a bit of a short and simple.

I’ve decided just to a few coding tips, I have come across and though might be useful for other devs, especially if you haven’t worked much with UIKit before in your development, or perhaps just these areas below. (At the bottom of this post is an Xcode project file which includes examples of the tips below).

Tip #1: Check for URL scheme and open correct app from your own
You’ll probably run into having to link to another app, for example your company’s Twitter account. Instead of just linking to the Twitter website, you can do a quick check in code and open the Twitter app instead. You can also do it with other Twitter client apps as well, however, not all have URL schemes setup (that I could find), and most users will probably be using the official one anyway. Regardless, the code is good to do the same check for other apps, or if doesn’t exists on the user’s device, you can try another Twitter client app, or use a UIAlertView to ask the user what else they’d like to use (depending on which ones are possible to open using the URL scheme).

Basically, all you have to do is ask whether UIApplication responds to the URL:

BOOL twitter = [[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"twitter://user?screen_name=runmad"]];
if (!twitter) {
	[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@""]];
} else {
	[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"twitter://user?screen_name=runmad"]];

List of URL Schemes:

Tip #2: Getting a free UINavigationController in your UIViewController
I have seen some apps that use a UIToolbar as a navigation bar, and this just doesn’t work. If you compare the two, they’re actually a bit different, and this really shows when put in the wrong place.

If you’ve got a UIViewController, turning it into a UINavigationController is really easy:

RootViewController *rootViewController = [[RootViewController alloc] init];
UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:rootViewController];
[self.navigationController presentModalViewController:navigationController animated:YES];
[rootViewController release];
[navigationController release];

Tip #3: Getting a free UIToolbar in your UINavigationController
This one I only just recently found out (thanks to @auibrian)
. UINavigationController actually comes with a UIToolbar. It’s property is set to hidden:YES by default, so all you have to do is override this property when you load the view.

[self.navigationController setToolbarHidden:NO];

Note: I have seen some weird behaviour when pushing view controllers onto the screen (buttons not getting a pushing animation, just appearing in the toolbar in place). Also, you will need to hide the toolbar if you’re popping or pushing to a view controller that you do not want to show the toolbar (because with pushing you’re reusing the same navigation controller). In my opinion it’s not a very good way, I wish the view controllers were more separate for this.

Tip #4: Use shadowColor and shadowOffset appropriately when faking text indention
One thing that bugs me are improper use of a UILabel’s shadowColor and shadowOffset. When using these, one has to pay attention to the colour of the background as well as the text colour. In the below example (when we’re going for the look where text looks carved into the display, used by Apple across the entire UI), we’ll see that when using darker text, use a lighter colour for the shadow and a positive value for the offset.

When displaying lighter coloured text, use a darker shadow colour and a negative value for the offset, which in both cases create the proper indented or “carved” effect.

Using the wrong combination doesn’t create this effect and makes the text appear raised from the rest of your UI, which is most likely not what you should be going for in most cases ;)

I’ve made a small Xcode project you can download here, which has the code examples from tips 1, 2 and 3 and I suppose #4 as well, since navigationItem.title is using text indention.

Again, apologies for a bit of a short and simple post due to being under the weather and traveling.

Quick guide to updating your app’s UI for iPhone 4

iPhone 4 will make your UI look stunning. Everything in UIKit has been scaled up already so it will require only a bit of work on your end to make the rest of your app look amazing on iPhone 4. If you only code and don’t touch Photoshop, you’re in luck. However, if you’re a UI designer or have the skills to do your own UI, hopefully you did your original artwork in a nice high resolution – if not, you have a bit of work cut out for you with updating all the UI elements to 2x the resolution.

Updating your app’s UI to be compatible with iPhone 4’s Retina Display is amazingly simple. Since the scale works in points, not pixels, you will have to do very little work on the layout itself. Apple Engineers have made it really simple to use new graphics for all your UI on iPhone 4, at the same time as being compatible (and not using 2x memory) on older, lower resolution, lower memory devices.

All you have to do is add the same image file at 2x the pixels to your app’s resources and name it the same it’s lower resolutions sibling with the following suffix: “@2x”.

For example, in your Resources folder, you will now need to have two image files, one for older devices called myImage.png and one for iPhone 4 called myImage@2x.png, which is twice the resolution.

This way, when you call [UIImage imageNamed:@”myImage.png”]; (or contentsOfFile:) iPhone 4 will automatically grab the filename with a @2x suffix, and lower resolution images will grab the lower resolution copy. You don’t have to check for the device loading the image and write any additional code to grab the correct image. Genius!

If you have seen an iPhone app on the iPad in 2x scale, that’s pretty much how your app is going to look on the iPhone 4. Perhaps not so drastic, but there will be a noticeable difference from app not optimized for iPhone 4 and “Retina Apps” as Apple calls them.

Thoughts on @2x on iPad…
I didn’t hear anything at WWDC regarding this, but my thought is that they’ll integrate this into the iPad for the next major OS release. Basically, it will be able to do the same and grab the higher resolution image appropriately for iPhone apps running at 2x scale.

Happy Photoshopping to UI designers and happy relaxing programmers!

UPDATE JULY 7, 2010:

I have discovered a bug in Apple’s code that deals with grabbing the correct image on iPhone 4. If you are using imageWithContentsOfFile: the code will in fact not automatically grab the @2x if running on iPhone 4. I have submitted a bug report to Apple, and they’ve informed me they are now aware of the issue and the Engineers are currently working to fix the bug. So for now, stick with imageNamed: for all your images.

Debugging Executables for Push Notifications

I am implementing Push Notifications in one of my apps. Doing so may be a bit tricky in terms of debugging since you cannot actually debug incoming Push Notifications appropriately while the app is running, so I wanted to share this tip. Also, I am writing this post on my iPad on an airplane, so pretty excited about that :)

Xcode allows you to debug applications that are running locally on your device. You can even set breakpoints in your code and print out any information you may need from the console in order to debug your app and fix whatever issue you’re experiencing, should you not be able to fix it via “live” debugging.

This feature is especially useful if you’re doing Push Notifications (a great way to easily communicate information to your user with their permission, such as notifications, reminders, marketing (be careful with this one), etc.).

With Push Notifications, your app receives data from Apple Push Notification servers in a dictionary in the UIApplication delegate application:didFinishLaunchingWithOptions: that you’ll need to parse and do in your app whatever is appropriate for the implementation you’ve chosen (launching with specific views in front, etc.). Since your app cannot be running while receiving Push Notifications (it actually does receive notifications while running, but you’re required to deal with that through another delegate method), you’ll need to use the “debug executables” with “Wait for next launch/push notifications” ticked. Once you run the debugger and launch your app (for example directly via a Push Notifications UIAlertView) you can set breakpoints anywhere in your code and use the console to print out (po) any objects you may wish to inspect.

As your app launches immediately when you debug, it’s a problem if you’re debugging Push Notification (which, by the way, does not work in Simulator). So here’s the hidden treasure in Xcode: In the Groups & Folder pane, find Executables, expand and select your app executable. Hit command+option+i to “Get Info” and select the Debugging tab. From here, tick “Wait for next launch/push notification”.

Now, when you Run & Debug your app it will not launch, but instead wait until you tap the app icon to launch it or the app is launched via a Push Notification UIAlertView (this of course requires you have not set the “action-loc-key” to null in your Push Notification JSON dictionary).

Once your app launches via a Push Notification, it will stop at the breakpoint you set and you can now print out any information you need to debug your app, such as the NSDictionary your app receives, whether the appropriate view will be displayed and any other issue you may have.

Some notes on UIView animation

UIView animation is a simple and nice way to add to your user experience. I just wanted to point out a few suggestions when using UIView animations.

Duration (speed):
If you choose to use animation to compliment some of the stuff already happening in UIKit, either at the same time or before/after, it makes a big difference how fast your animations are. Pretty much all the UIKit animations I have come across have a duration of 0.3f and so should yours. Of course, it’s doesn’t always work 100% but for the most part, 0.3f is what you should aim for. It’s quick so your user don’t wait for something to finish animating before continuing with the next input action, and it’s not too fast so that the user doesn’t have a chance to see where the object came from or what happened.

If you have an animation happening while the keyboard animates up or down, use an animationDuration of 0.3f. Same with pushing and popping the navigationController. Annotations in MKMapView also drop at a duration of 0.3f.

0.3f is the way to go.

A simple UIView animation can be added with the following code:

[UIView beginAnimations:nil context:nil];
[UIView setAnimationDuration:0.3f];
self.segmentControl.alpha = 1.0f;
[UIView commitAnimations];

The above example is from an app I’m doing, where the segmentControl is enabled and I increase its visibility in the toolBar at the same rate as a pin drops in the map within the same screen.

When to use animation:
A few objects come with free animation (also at a duration of 0.3f, of course). For example, when adding a UIBarButton to your UINavigationBar, consider setting these with animation. If you replace a UIBarButton with another, they’ll even animate in and out nicely during the change. When adding a pin to a map, why not drop it onto the map with an animation, instead of it suddenly appearing on a map from nowhere?

Another good advice is to do animation (whether your own or with objects that include animations) to bring attention to an object. For example, if you have a pushed view, consider what you can “add” after the view has appeared through animating your objects in viewDidAppear.

Create a better UX with animation
Consider all the ways you can use UIView animation blocks in your app to enhance the user experience. It’s a great way to create a more fluid and pleasant experience for your users. A user’s inputs and actions will feel less rough and more smooth and soft to the touch. Don’t go overboard with animations. Too many will become annoying and it’s important to use animations only where appropriate.

The best advice is probably to have a look at many of the built in apps designed by Apple as well as the many free animations that a part of UIKit objects (how UIBarButtons animate in and out when you push a UIViewController stack, how a modal view appears from the bottom, etc.).

UITabBarController and UIActionSheet – 65% less hit point!

Ever noticed an app where the UIActionSheet’s bottom button doesn’t want to respond to your taps, unless you hit exactly in the top of the button? If you have a UITabBarController and want to display a UIActionSheet, you have to be careful with what view you show the UIActionSheet in.

If a UIActionSheet is shown in “self” or “self.view” and you got a UITabBarController behind it less than half of the last button will respond to taps:

UIActionSheet *actionSheet = [[UIActionSheet alloc] initWithTitle:@"UIActionSheet Title" delegate:nil cancelButtonTitle:@"Cancel" destructiveButtonTitle:nil otherButtonTitles:@"Option 1", @"Option 2", nil];
actionSheet.actionSheetStyle = UIActionSheetStyleBlackTranslucent;
[actionSheet showInView:self];
[actionSheet release];

Here’s how much of the button will actually respond to taps:

Here’s what you need to do to fix it:

[actionSheet showInView:[[[UIApplication sharedApplication] windows] objectAtIndex:0]];

And what it does:

Colouring fun with moreNavigationController

When adding more than 5 view controllers to your UITabBarController, a “More” tab is automatically setup for you, which includes a view controller and even a modal view for letting the user edit the app’s tabs in the order they want.

By default, the navigation bars for both the moreNavigationController and the modal view (edit) are the Default blue, but changing these colours isn’t exactly straightforward.

Here’s an example of what we want to achieve:

I use an orange colour in one of my apps for the navigation bars and it just looks wrong when the more tab’s navigation bars are blue.

Changing the colour of the moreNavigationController is quite easy. After you alloc the UITabBarController, set the colour of the moreNavigationController:

tabBarController.moreNavigationController.navigationBar.tintColor = [UIColor orangeColor];

You can also use the barStyle property if you like:

tabBarController.moreNavigationController.navigationBar.barStyle = UIBarStyleBlackOpaque;

That wasn’t so hard. But the navigation bar for the modal view that pops up when the user taps “Edit” is still the default blue. So let’s change that as well:

First, if you haven’t already, make sure your AppDelegate implements the UITabBarControllerDelegate. Then add the optional delegate method willBeginCustomizingViewControllers: in your AppDelegate’s implementation file, and add the following lines of code:

– (void)tabBarController:(UITabBarController *)controller willBeginCustomizingViewControllers:(NSArray *)viewControllers {
    UIView *editView = [controller.view.subviews objectAtIndex:1];
    UINavigationBar *modalNavBar = [editView.subviews objectAtIndex:0];
    modalNavBar.tintColor = [UIColor orangeColor];

Again, it’s possible to set the barStyle property instead of the tintColor, but barStyle won’t give you all the colour options, of course.

Now that you have gained control of the modal view, you change more properties. By default, the navigation bar title says “Configure”, but you can change that as well, or how about the background colour? Here’s how:

– (void)tabBarController:(UITabBarController *)controller willBeginCustomizingViewControllers:(NSArray *)viewControllers {
    UIView *editView = [controller.view.subviews objectAtIndex:1];
    editView.backgroundColor = [UIColor grayColor];
    UINavigationBar *modalNavBar = [editView.subviews objectAtIndex:0];
    modalNavBar.tintColor = [UIColor orangeColor];
    modalNavBar.topItem.title = @"Edit Tabs";

Regarding the HIG… I am not sure if all this is allowed. I will be submitting an update with an orange coloured navigation bar for both those views, and I believe other apps have it (NY Times) so I don’t think it goes against the HIG.

However, I don’t think it’s a good idea to change the backgroundColor property of the “editView”. I tried with a grey colour and it doesn’t look right. It might also get your app rejected, because it’s such a big change. That your navigation bars are the same colour throughout your app only makes it look better in my opinion, rather than having a blue navigation bar clash with the rest of your beautifully designed app :)