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 Twitter.app 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:@"http://www.twitter.com/runmad"]];
} else {
	[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"twitter://user?screen_name=runmad"]];
}

List of URL Schemes: http://wiki.akosma.com/IPhone_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.