NSHipster Call for Tips & Tricks!

NSHipster-Call-For-Tricks-And-Tips.md

Howdy howdy, NSHipsters!

If you alloc init an NSCalendar, you'll notice that New Year's Eve falls on a Monday this year, a.k.a. "the day NSHipster is published every week". What fun!

So in celebration of the upcoming year++, I thought it'd be fun to compile a list of some of your favorite tips and tricks of the trade. Submit your favorite piece of Objective-C trivia, framework arcana, hidden Xcode feature, or anything else you think is cool, and you could have it featured in the year-end blowout article. Just comment on this gist below!

Here are a few examples of the kind of things I'd like to see:

• StaticObjcMethods from [Apple]((http://developer.apple.com/library/mac/#samplecode/CocoaTipsAndTricks/Introduction/Intro.html): Demonstrates how to use static Objective-C methods that have access to ivars.
• NSArray Slicing from Mike Ash: A sugary syntax for slicing array, with a clever use of subscripting.
• Texts From Xcode: Absolutely brilliant--makes me laugh every time. A must-follow on Twitter or Tumblr.

Again, just comment on this Gist below with your submission.

Can't wait to see what y'all come up with!

See function static id _target(id autoContentAccessingProxy) for accessing a private ivar. You should obviously never ship your app with such code but it may be helpful for debugging.

extern NSString *const and weak linking does’t work the way you think it works, from https://gist.github.com/3725528:

#import <Social/Social.h>

/* Compiled with iOS 6 SDK
 * Social.framework weak linked (Optional)
 * Run on iOS 5.1 (simulator and device)
 * Output is:
 * 0x0
 * About to crash
 * +++ EXC_BAD_ACCESS +++
 */

int main(int argc, char *argv[])
{
    @autoreleasepool
    {
        NSLog(@"%p", &SLServiceTypeFacebook);
        if (&SLServiceTypeFacebook)
        {
            NSLog(@"About to crash");
            NSString *serviceType = SLServiceTypeFacebook; // crashes here with EXC_BAD_ACCESS (code=2, address=0x0)
            NSLog(@"Not reached %@", serviceType);
        }
    }
    return 0;
}

Reverse-engineered implementation of -[NSString isEqual:] and -[NSString isEqualToString:]

Using NSPropertyListSerialization to implement base64 encoding and decoding in less than 50 lines with support for iOS 2.0 and OS X 10.5.

How about associated objects? You know it’s going down when you see this at the top of one of my files:

#import <objc/runtime.h>

static const void *kMyKey = &kMyKey;

In iOS 6 you can animate a constant property in NSLayoutConstraint:

viewConstraint.constant = ConstantValueFrom;
[view layoutIfNeeded];

viewConstraint.constant = ConstantValueTo;
[view setNeedsUpdateConstraints];

[UIView animateWithDuration:ConstantAnimationDuration animations:^{
     [view layoutIfNeeded];
}];

Printing NSCache usage information (tested on iOS only):

extern void cache_print(void *cache);

- (void) printCache:(NSCache *)cache
{
    cache_print(*((void **)(__bridge void *)cache + 3));
}

Use for debugging only!

Thanks again, everyone, for your great submissions! These have now been compiled into this special New Year's Eve Edition of NSHipster. Cheers!