Scott Berrevoets

Any developer that has worked with Xcode to write a little more than just "Hello, World" knows that Xcode and Objective-C have their quirks. Chances are you have heard of @TextFromXcode, the Twitter handle that portrays Xcode as a high school bully in fake text conversations like this:

But it's not always Xcode that makes Apple platform developers sometimes frown and sigh. Sometimes it's the developers themselves, sometimes it's the documentation, and sometimes a hidden gem from within Apple frameworks makes an appearance. I've compiled a short list of things I've encountered. Because it's Sunday and I didn't have anything better to do.

UIGobblerGestureRecognizer

Say what? A "gobbler" recognizer? Does it recognize when the user imitates a turkey? Well, maybe, but according to BJ Homer, it is used to avoid recognition of a gesture while animations are in progress. Ah of course! Now the name "gobbler" makes perfect sense! 😶

UITapAndAHalfRecognizer

Speaking of gesture recognizers, there's another remarkable one that lives in the private section of UIKit: UITapAndAHalfRecognizer. This is a private subclass of UIGestureRecognizer that records "a tap and a half".

So what does that mean? Does it detect whether the user goes in for a second tap, but never actually touches the screen? Or does the user touch the screen ever so slightly that the second tap can hardly be considered a complete tap? Nope! This recognizer fires when a second tap stays on the screen. Not sure for what functionality Apple needs this, but it's been around since at least iOS 4, so it probably has a purpose.

Naming is hard

There are only two hard things in Computer Science: cache invalidation and naming things.
- Phil Karlton

Naming is hard, but Objective-C developers always say that verbosity is one of Objective-C's strengths because its naming conventions are self-documenting. Normally I'd agree, but in this case, I think Apple may want to consider a different name.

HMCharacteristicValueLockMechanismLastKnownActionUnsecuredUsingPhysicalMovementExterior is a brand new constant in iOS 8 and has got to be one of the longest constants that's available in iOS. Try saying it without taking a breath in the middle.

I found it in the iOS 8 API diffs, but it did make me wonder. What is the longest Objective-C method available in Cocoa Touch? Well, a quick Google search led to a blog post by Stuart Sharpe, who used the Objective-C runtime to generate a list of methods in the iOS 7 SDK.

Turns out, the longest method in the iOS 7 SDK is

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22

+[CUIShapeEffectStack shapeEffectSingleBlurFrom:
                               withInteriorFill:
                                         offset:
                                       blurSize:
                                   innerGlowRed:
                                 innerGlowGreen:
                                  innerGlowBlue:
                               innerGlowOpacity:
                                 innerShadowRed:
                               innerShadowGreen:
                                innerShadowBlue:
                             innerShadowOpacity:
                                   outerGlowRed:
                                 outerGlowGreen:
                                  outerGlowBlue:
                               outerGlowOpacity:
                                 outerShadowRed:
                               outerShadowGreen:
                                outerShadowBlue:
                             outerShadowOpacity:
                            hasInsideShadowBlur:
                           hasOutsideShadowBlur:]

Unless iOS 8 introduces a longer method name, this one takes the cake with 22 arguments and 352 characters. If you have Xcode configured to line-break at 80 characters (yes, some people still do that), this method signature alone, without any arguments, takes up 5 lines.

Another beauty of a method lives in Core Animation and its method signature is

1

- [CAMediaTimingFunction functionWithControlPoints::::]

::::? Is that even valid syntax? Yes, and you call the method like this:

1

[CAMediaTimingFunction functionWithControlPoints:0.25 :.50 :0 :1.0];

Was an array really too much to ask...?

[NSDate nilDate]

This one has made the rounds throughout the developer community before, but I'm adding it here in case you haven't seen it yet. Try running the following code:

1
2

NSCalendar *calendar = [NSCalendar currentCalendar];
[calendar components:NSCalendarUnitYear fromDate:nil toDate:[NSDate date] options:0];

In the console log, you'll find the following output:

*** -[__NSCFCalendar components:fromDate:toDate:options:]: fromDate cannot be nil
I mean really, what do you think that operation is supposed to mean with a nil fromDate?
An exception has been avoided for now.
A few of these errors are going to be reported with this complaint, then further violations will simply silently do whatever random thing results from the nil.

Either a grumpy Apple developer woke up at the wrong side of the bed or has a great sense of humor. In any case, I wouldn't mind if more sarcastic warnings started popping up in Xcode's console.

Defying the Uncertainty Principle in iOS

[I]n 1927, Werner Heisenberg stated that the more precisely the position of some particle is determined, the less precisely its momentum can be known, and vice versa.
Wikipedia

If that's true, and it's fairly safe to assume that it is, I'd avoid using -[CLLocation speed] for apps like radar detectors. I wonder if we're ever going to get a -[CLSpeed location] method, which has a more accurate speed and a less accurate location.

Xcode at it again

Lastly, the following is a screenshot I personally took at work that completely baffled me.

This would not go away, even after cleaning the build folder and rebuilding. In the end I resolved the problem by running

1
2

$ git stash
$ git reset --hard HEAD

Then, after a clean build and git stash pop the errors finally went away...

That's just a few things I've found while working with Xcode and Objective-C over the years. If you have more, please share!