Thursday, December 15, 2011

Migrating to UIStoryboard

I’ve just recently started using UIStoryboard and so far I’ve been very pleased with it. Building the UI is faster, easier, and requires less code. It’s also immensely helpful to get a bird’s eye view of your full workflow. However, when migrating an old app from using regular XIBs to UIStoryboard I did encounter some troubles. When launching the app, I would get the following error messages:

“The app delegate must implement the window property if it wants to use a main storyboard file.”
“Applications are expected to have a root view controller at the end of application launch.”

I could clearly see that my app delegate was implementing the window property as expected. Fortunately, StackOverflow came to the rescue. It turns out that main.m needs to be modified when switching to UIStoryboard from XIBs (in older projects). The change looks like this:

// Old main.m
UIApplicationMain(argc, argv, nil, nil);

// New main.m
UIApplicationMain(argc, argv, nil, NSStringFromClass([MyAppDelegate class]));

The documentation for this parameter reads:

The name of the class from which the application delegate is instantiated. If principalClassName designates a subclass of UIApplication, you may designate the subclass as the delegate; the subclass instance receives the application-delegate messages. Specify nil if you load the delegate object from your application’s main nib file.

Basically, if you aren’t using XIBs, you must let UIApplication know what your app delegate’s name is. You will also notice that any new projects created with the latest version of Xcode will specify the app delegate, even if you are using XIBs. This prevents any problems should you migrate to UIStoryboard later.

UIColor Category

For a long time I’ve wanted more convenience methods for UIColor. The set Apple provides is a nice starting point but I often find myself wanting more. In particular, the Mac color picker has a crayon box color picker with common colors. Sadly, there are no convenience methods for these colors. Since I use them so frequently, I decided to put them all in a category. This was tedious work since I had to do them one-by-one by hand.

After getting these 48 convenience methods I figured why stop there. I moved on to the HTML colors. At the time I didn’t realize how many standard HTML colors exist (147). After seeing that number I almost threw out the idea, but I remembered that @alesplin taught how to use Vim macros in the November BYU CocoaHeads meeting. Using a list of HTML colors and their associated hex values, I had all 147 HTML color convenience methods finished within minutes. Vim may be an old, crusty text editor, but its macro editing power is unmatched by modern IDEs.

If you want a copy of my UIColor category, you can find it in my RBCategories repo on Github.