# Reader Submissions - New Year's 2013 By [Mattt](https://nshipster.com/authors/mattt). Published 2013-01-01. Canonical URL: In celebration of the forthcoming `year++`, I thought it’d be fun to compile a list of some of _your_ favorite tips and tricks of the trade–to give y’all a chance to show off some of your NSHipster cred. Thanks to [Cédric Luthi](https://github.com/0xced), [Jason Kozemczak](https://github.com/jaykz52), [Jeff Kelley](https://github.com/SlaunchaMan), [Joel Parsons](https://github.com/joelparsons), [Maximilian Tagher](https://github.com/MaxGabriel), [Rob Mayoff](https://github.com/mayoff), [Vadim Shpakovski](https://github.com/shpakovski), & [@alextud](https://github.com/alextud) for [answering the call](https://gist.github.com/4148342) with _excellent_ submissions. ## Associated Objects in Categories This first tip is so nice it was mentioned twice, both by [Jason Kozemczak](https://github.com/jaykz52) & [Jeff Kelley](https://github.com/SlaunchaMan). Categories are a well-known feature of Objective-C, allowing new methods to be added to existing classes. Much less well known is that with some `objc` runtime hacking, you can add new _properties_ as well. Observe! ### NSObject+IndieBandName.h ```objc @interface NSObject (IndieBandName) @property (nonatomic, strong) NSString *indieBandName; @end ``` ### NSObject+IndieBandName.m ```objc #import "NSObject+IndieBandName.h" #import static const void *IndieBandNameKey = &IndieBandNameKey; @implementation NSObject (IndieBandName) @dynamic indieBandName; - (NSString *)indieBandName { return objc_getAssociatedObject(self, IndieBandNameKey); } - (void)setIndieBandName:(NSString *)indieBandName { objc_setAssociatedObject(self, IndieBandNameKey, indieBandName, OBJC_ASSOCIATION_RETAIN_NONATOMIC); } @end ``` This way, all of your objects can store and retrieve the name of their band, which–by the way–is performing this Wednesday night, and you should totally come. While this is a cool trick and all, it should only be used as a method of last resort. Before you go this route, ask yourself if a particular property can’t either be derived from existing values, or should be managed by another class. A good example of an associated object is how [AFNetworking](https://github.com/AFNetworking/AFNetworking) adds a property for an image request operation in its [`UIImageView` category](https://github.com/AFNetworking/AFNetworking/blob/master/AFNetworking/UIImageView%2BAFNetworking.m#L39). ## LLDB View Hierarchy Dump [Rob Mayoff](https://github.com/mayoff) responded with an obscure and powerful incantation to make debugging views a delight. Create `.lldbinit` in your home directory, if it doesn’t already exist, and add the following: ### \~/.lldbinit ``` command regex rd 's/^[[:space:]]*$/po [[[UIApplication sharedApplication] keyWindow] recursiveDescription]/' 's/^(.+)$/po [%1 recursiveDescription]/' ``` Now you can get a recursive hierarchy of any view in your iOS application with the LLDB debugger. You can try this for yourself by setting a breakpoint in a view controller, and typing `rd self.view`. You may be surprised by what’s under the hood with some of the built-in UI controls! ## LLDB Print Contents of a `CGPathRef` While we’re on the subject of LLDB, [Rob Mayoff](https://github.com/mayoff) sent in a useful incantation for printing out the contents of a `CGPathRef` from the debugger: ``` p (void)CGPathPrint(pathRef, 0) ``` If you’re doing any kind of complex Core Graphics drawing, be sure to keep this one handy. ## Use `+initialize`, Not `+load` [Vadim Shpakovski](https://github.com/shpakovski) wrote in with some advice about class loading and initialization. There are two magical class methods in Objective-C: `+load` and `+initialize`, which are automatically called by virtue of the class being used. The difference between the two methods, however, has significant performance implications for your application. [Mike Ash](http://www.mikeash.com/) has a [great explanation of this](http://www.mikeash.com/pyblog/friday-qa-2009-05-22-objective-c-class-loading-and-initialization.html): > `+load` is invoked as the class is actually loaded, if it implements the method. This happens very early on. If you implement `+load` in an application or in a framework that an application links to, `+load` will run before `main()`. If you implement `+load` in a loadable bundle, then it runs during the bundle loading process. > The `+initialize` method is invoked in a more sane environment and is usually a better place to put code than `+load`. `+initialize` is interesting because it’s invoked lazily and may not be invoked at all. When a class first loads, `+initialize` is not called. When a message is sent to a class, the runtime first checks to see if `+initialize` has been called yet. If not, it calls it before proceeding with the message send. **tl;dr: Implement `+initialize`, not `+load`, if you need this automatic behavior.** ## Xcode Snippets [Maximilian Tagher](https://github.com/MaxGabriel) gave a shout-out to the benefits of Xcode Snippets. Great developers take pride in knowing their tools, and being able to use them to maximum effect. [For better](https://twitter.com/javisoto/status/285531250373046272) or [for worse](http://www.textfromxcode.com/), this means knowing Xcode like the back of our hand. Verbose as Objective-C is, “do more by typing less” rings especially true as a productivity mantra, and [Xcode Snippets](https://developer.apple.com/library/mac/#recipes/xcode_help-source_editor/CreatingaCustomCodeSnippet/CreatingaCustomCodeSnippet.html#//apple_ref/doc/uid/TP40009975-CH14-SW1) are one of the best ways to do this. If you’re looking for a place to start, try downloading and forking [these Xcode Snippets](https://github.com/mattt/Xcode-Snippets). ## Macro for Measuring Execution Time Here’s a helpful macro for easily measuring the elapsed time for executing a particular block of code, sent in from [@alextud](https://github.com/alextud): ```objc NS_INLINE void MVComputeTimeWithNameAndBlock(const char *caller, void (^block)()) { CFTimeInterval startTimeInterval = CACurrentMediaTime(); block(); CFTimeInterval nowTimeInterval = CACurrentMediaTime(); NSLog(@"%s - Time Running is: %f", caller, nowTimeInterval - startTimeInterval); } #define MVComputeTime(...) MVComputeTimeWithNameAndBlock(__PRETTY_FUNCTION__, (__VA_ARGS__)) ``` ## Block Enumeration Methods [Joel Parsons](https://github.com/joelparsons) submitted a great tip about using `-enumerateObjectsWithOptions:usingBlock:` in `NSArray` and other collection classes. By passing the `NSEnumerationConcurrent` option, you can get significant performance benefits over `NSFastEnumeration`’s `for...in`-style enumeration by executing the block concurrently. However, be warned! Not all enumerations lend themselves to concurrent execution, so don’t go around replacing all of your `for...in` blocks with `NSEnumerationConcurrent` willy-nilly, unless random crashing is something you like in an app. ## Reverse-Engineered Implementation of `NSString` Equality Methods Displaying his characteristic brilliance and familiarity of Cocoa internals [Cédric Luthi](https://github.com/0xced) submitted [a reverse-engineered implementation of the `NSString` equality methods](https://gist.github.com/2275014). Fascinating! ## Animate `NSLayoutConstraint.constant` This one goes out to all you fans of [Cocoa Auto Layout](https://developer.apple.com/library/mac/#documentation/UserExperience/Conceptual/AutolayoutPG/Articles/Introduction.html#//apple_ref/doc/uid/TP40010853), from [Vadim Shpakovski](https://github.com/shpakovski): ```objc viewConstraint.constant = <#Constant Value From#>; [view layoutIfNeeded]; viewConstraint.constant = <#Constant Value To#>; [view setNeedsUpdateConstraints]; [UIView animateWithDuration:ConstantAnimationDuration animations:^{ [view layoutIfNeeded]; }]; ``` Attentive readers may have already noted this, but the code above would make an _excellent_ Xcode Snippet, by the way. ## Printing `NSCache` Usage Finishing up this batch of tips and tricks is [Cédric Luthi](https://github.com/0xced) again, this time unearthing the private method `cache_print` as a way to get some visibility into [`NSCache`](https://nshipster.com/nscache/): ```objc extern void cache_print(void *cache); - (void) printCache:(NSCache *)cache { cache_print(*((void **)(__bridge void *)cache + 3)); } ``` This code sample has only been tested on iOS, and should only be used for debugging (i.e. take this out before submitting to Apple!). --- Thanks again to everyone for their submissions this time around. We’ll definitely be doing this again, so feel free to send your favorite piece of Objective-C trivia, framework arcana, hidden Xcode feature, or anything else you think is cool to [@NSHipster](https://twitter.com/nshipster)! And thank you, dear reader, for your support of NSHipster over these last wonderful months. We have a lot of insanely great things planned for NSHipster in 2013, and we look forward to being able to share it all with all of you.