Small Helper Objects Take You Far

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Integrating new functionality is fun. But revisiting 18-months old code isn’t. Back then I created a protocol InvokesWindows to define methods like -showPreferencesWindow which I imported in the menu bar controller to show the preferences when the user selects a pop-up menu item. But I didn’t actually delegate to any instance of InvokesWindows. I used NSApp. (Insert facepalm here.)

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Dismissing a Modally Presented Scene on Both iPad and iPhones Using Unwind Segues

UISplitViewController is the way to go when you want to make your iOS app universal without much hassle and can model the scenes in terms of master/detail. While getting Calendar Paste ready for the upcoming iOS 9 release, I discovered that using UISplitViewController across devices is one thing, while Storyboard segues are another.

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Generics in Objective-C

Objective-C got generics! No more collection classes just for the sake of guarding against invalid elements!

I used custom collection classes a lot for the Word Counter to let the compiler help me prevent mistakes. Swift generics were a godsend for that kind of safety. Now, Objective-C can achieve similar awesomeness.

It can look like this:

@interface Wheel : NSObject
@property (nonatomic, strong) UIColor *color;

@interface Vehicle : NSObject
@property (nonatomic, copy) NSArray<Wheel *> *wheels;

Now the compiler will warn (!) you if you misuse it:

Vehicle *car = [[Vehicle alloc] init];
[car.wheels addObject:@"NSString is of the wrong type"];

Great news, since if you didn’t spend a lot of time creating custom collection types yourself, now at last can you ensure array element type consistency. Makes your code cleaner and more reliable.

Test doubles for Core Data managed objects might not work as expected

You don’t have to learn anything new if you work with Core Data in Swift. It’s a pain to use NSManagedObject directly, so you better work with custom subclasses all the time. Unboxing optional NSNumbers is just too cumbersome. There are caveats you should be aware of, though: Swift’s static typing makes it a bit harder to write test doubles for managed objects.

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Success and Error Callbacks in Objective-C: a Refactoring

I’m refactoring code of Calendar Paste 2 some more. Since I like what I learned using Swift so much, one of today’s changes was about making a view controller method do less by factoring object creation and error handling into its collaborators. The resulting code handles far less of the action involved. Instead, it delegates the action to a new command-like object. And instead of querying an event template for data and assembling an actual event with start and end dates, it delegates event creation to the template itself. Tell, Don’t Ask saved the day.

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