# Reader Submissions - New Year's 2014 By [Mattt](https://nshipster.com/authors/mattt). Published 2014-01-01. Canonical URL: As we prepare to increment our `NSDateComponents -year` by `1`, it’s time once again for NSHipster end-of-the-year Reader Submissions! [Last year](https://gist.github.com/mattt/4148342), we got some [mind-blowing tips and tricks](https://nshipster.com/reader-submissions-new-years-2013/). With the release of iOS 7 & Mavericks, and a year’s worth of new developments in the Objective-C ecosystem, there was a ton of new stuff to write about. Thanks to [Arnaud Coomans](https://github.com/acoomans), [Cédric Luthi](https://github.com/0xced), [David Grandinetti](https://github.com/dbgrandi), [Ell Neal](https://github.com/ellneal), [Eric Allam](https://github.com/rubymaverick), [Erik Kerber](https://github.com/eskerber), [Jim Kubicek](https://github.com/jkubicek), [Joachim Bengtsson](https://github.com/nevyn), [Johannes Lund](https://github.com/Anviking), [Josh Avant](https://github.com/joshavant), [João Prado Maia](https://github.com/jpm), [Justin R. Miller](https://github.com/incanus), [Kamil Pyć](https://github.com/PycKamil), [Matthew Teece](https://github.com/mteece), [Maximilian Tagher](https://github.com/MaxGabriel), [Nigel Timothy Barber](https://github.com/mindbrix), [Nolan O’Brien](https://github.com/NSProgrammer), [Pitiphong Phongpattranont](https://github.com/pitiphong-p), [Steve Moser](https://gist.github.com/stevemoser), [Thomas Visser](https://github.com/Thomvis), [Vadim Shpakovski](https://github.com/shpakovski), & [@jurre](https://github.com/jurre) for [contributing their great tips](https://gist.github.com/7414618). --- ## GCC Code Block Evaluation C Extension Let’s make this official: **NSHipster’s Objective-C trend of 2013 is code block evaluation assignment**. Recommended by both [Jim Kubicek](https://github.com/jkubicek) and [Maximilian Tagher](https://github.com/MaxGabriel) (citing [this blog post](http://cocoa-dom.tumblr.com/post/56517731293/new-thing-i-do-in-code) by [Dominik Wagner](https://github.com/monkeydom)), this trick does wonders to make code cleaner, safer, and more concise. Behind the magic is a GCC C extension, which causes a code block to return a value if enclosed within brackets and parentheses. Watch, as it cuts through this view controller code like butter! ```objc self.searchBar = ({ UISearchBar *searchBar = [[UISearchBar alloc] initWithFrame:({ CGRect frame = self.tableView.frame; frame.size.height = 50.0f; frame; })]; searchBar.delegate = self; searchBar; }); ``` This not only segregates configuration details into initialization, but the additional scope allows generic variable names like `frame`, `button`, and `view` to be reused in subsequent initializations. No more `loginButtonFrame = ... / signupButtonFrame = ...`! If code craftsmanship is important to you, strongly consider making this standard practice in your work. It may look a bit weird at first, but this will very likely become common convention by the end of 2014. ## Default Values with GNU-style Ternary `?:` The ternary operator, `?`, is shorthand for `if () {...} else {...}`. However, because of how difficult it can be to understand statements with ternary operators at a glance, they are generally dispreferred by veteran coders. Nonetheless, [Maximilian Tagher](https://github.com/MaxGabriel) offers a lesser-known (yet much-loved by those in-the-know) use of the ternary operator: `?:`, which acts as a convenient way to specify a fallback value to return if the left-hand side is `nil`. ```objc NSLog(@"%@", @"a" ?: @"b"); // @"a" NSLog(@"%@", nil ?: @"b"); // @"b" ``` This is especially convenient for providing default behavior when a property may not be set: ```objc dispatch_async(self.completionQueue ?: dispatch_get_main_queue(), ^{ <#…#> }); ``` The main downside of this approach is that default Xcode project warning settings will raise a warning. You can get around this by wrapping the relevant code block in `#pragma` declarations, but the added LOC nullifies much of the brevity that this approach provides: ```objc #pragma clang diagnostic push #pragma clang diagnostic ignored "-Wgnu" self.name = name ?: @"Unknown"; #pragma clang diagnostic pop ``` ## `@import` [Vadim Shpakovski](https://github.com/shpakovski) reminds us of one of the more obscure additions to LLVM 5.0, the `@import` keyword. No more are the days of `Xcode ▹ Project ▹ TARGETS ▹ General ▹ Linked Frameworks and Libraries ▹ +`. With `@import`, Xcode will automatically link `MapKit`, `CoreData`, or any other referenced framework as necessary. Even `Prefix.pch` benefits, sporting a svelte new physique: ```objc @import UIKit; @import Foundation; @import CoreGraphics; ``` ## Customizing MKMapView Tiles [Justin R. Miller](https://github.com/incanus), of [MapBox](https://www.mapbox.com/) fame, brings to our attention what is perhaps the most important feature in iOS 7 mapping: custom tile overlays: > Relatively little-known feature of iOS 7: you can turn off Apple’s own maps now with `MKTileOverlay`, `MKTileOverlayRenderer`, and `canReplaceMapContent`, unlike you could before with Apple or (pre-iOS 6) Google. And check out [MBXMapKit](http://github.com/mapbox/mbxmapkit) if you’d like to do it in one line of code. ## Thoughtbot’s Blog Post on MapKit Performance Speaking of iOS maps, [João Prado Maia](https://github.com/jpm) cites an amazing blog post by [thoughtbot](http://thoughtbot.com/), [“How To Efficiently Display Large Amounts of Data on iOS Maps”](http://robots.thoughtbot.com/how-to-handle-large-amounts-of-data-on-maps) by [Theodore Calmes](https://twitter.com/theocalmes). Consider it a must-read if you plan to do any significant iCartography in 2014. ## NSAttributedString + HTML in iOS 7 Shifting gears a little bit, [Eric Allam](https://github.com/rubymaverick) remarks that `NSAttributedString` can do HTML now in iOS 7 with the new [`NSHTMLTextDocumentType`](https://developer.apple.com/library/ios/documentation/UIKit/Reference/NSAttributedString_UIKit_Additions/Reference/Reference.html#//apple_ref/doc/uid/TP40011688) document type attribute. Combine with [MMMarkdown](https://github.com/mdiep/MMMarkdown) for ridiculously easy [Markdown rendering in a `UITextView`](http://initwithfunk.com/blog/2013/09/29/easy-markdown-rendering-with-nsattributedstring-on-ios-7/). --- ## Launch Arguments & User Defaults Offering another tip, [Vadim Shpakovski](https://github.com/shpakovski) calls our attention to the relationship between launch arguments and `NSUserDefaults`: The command line argument `-TestFeatureEnabled YES` can be checked in code with `[[NSUserDefaults standardUserDefaults] boolForKey:@"TestFeatureEnabled"]`. This is useful for debugging development builds. --- ## Woes of a Missing `UIViewAnimationCurve` Value [Thomas Visser](https://github.com/Thomvis) bemoans his pick for least awesome Objective-C development in 2013: > In iOS7, the animation of the keyboard show/hide changed. Its duration and, most notably, its curve is different from previous iOS versions. As before, if you want to animate something with the keyboard, you can listen to `UIKeyboardWillShowNotification`/`UIKeyboardWillHideNotification` and use the values from the `userInfo` dictionary to coordinate your animations with the keyboard. The `userInfo` dictionary contains the keyboard’s begin frame, end frame, animation curve and animation duration. > However, in iOS 7, the animation curve is an undefined value, meaning that it is not one of the 4 defined values of `UIViewAnimationCurve`. Instead, its value is `7`. This is a problem if you want to use the same curve in your own animation, because such a curve is not defined. The work-around, [as discussed on the Apple forums](https://devforums.apple.com/message/878410#878410), is to manually translate the `UIViewAnimationCurve` to a `UIViewAnimationOptions` value. From the definition of `UIViewAnimationOptions`, we learn that this translation is done by shifting the curve value 16 times to the left: `option = curve << 16`. This works great, but shouldn’t be necessary. I hope Apple will add this mysterious 5th curve to the definitions in a future iOS update. ## Injecting Analytics on Outgoing Links [David Grandinetti](https://github.com/dbgrandi) has a tip for apps that want to track outgoing links from within an app: override `UIApplication -openURL:` in a subclass: ```objc -(BOOL)openURL:(NSURL *)url{ if ([[url scheme] hasPrefix:@"http"]) { [[GAI sharedInstance].defaultTracker sendView:[url absoluteString]]; } return [super openURL:url]; } ``` In this example, this information is being sent to Google Analytics, but one could easily adapt this approach for any analytics provider. ## Reviving the Look-and-Feel of iOS 6 in Your App with One Weird Trick (UI Designers _hate_ it!) Still resisting the aesthetics of this year’s iOS makeover? [Kamil Pyć](https://github.com/PycKamil) shows us how to act as if iOS 7 never happened: ```objc [[NSUserDefaults standardUserDefaults] setObject:@YES forKey:@"UIUseLegacyUI"]; ``` > And, of course, following up from a previous tip, since `NSUserDefaults` is tied to launch arguments, this can also be specified on launch. Keep this tucked in the back of your mind—this could make for a simple yet effective April Fool’s joke. --- ## Detecting Category Method Collisions Categories are great, but suffer from that same original sin of Objective-C: lack of name-spacing. Duplicate method declarations in categories interact in undefined ways, and may lead to difficult-to-debug behavior. Fortunately, [Cédric Luthi](https://github.com/0xced) shows us how to tell if any category methods are getting up in one another’s business: > Set the `OBJC_PRINT_REPLACED_METHODS` environment variable to `YES` in order to automatically log all methods that are smashed by categories. --- ## A .plist of Emoji, Grouped by Category In an encore submission, Cédric brings us a [.plist file of Emoji grouped by category](https://gist.github.com/mattt/8185075) (mirrored from CloudApp to Gist in order to be more searchable). 😄👍 --- ## Quickly Determining the Type of Image Data Here’s a simple function from [Nolan O’Brien](https://github.com/NSProgrammer) that can be used to determine the type of image data based on the first couple bytes of the header: ```objc static inline NSPUIImageType NSPUIImageTypeFromData(NSData *imageData) { if (imageData.length > 4) { const unsigned char * bytes = [imageData bytes]; if (bytes[0] == 0xff && bytes[1] == 0xd8 && bytes[2] == 0xff) { return NSPUIImageType_JPEG; } if (bytes[0] == 0x89 && bytes[1] == 0x50 && bytes[2] == 0x4e && bytes[3] == 0x47) { return NSPUIImageType_PNG; } } return NSPUIImageType_Unknown; } ``` --- ## Print KVO Context Once again, showing off his unmatched knowledge of Objective-C internals, Cédric shares this extremely useful tip for debugging [Key-Value Observing](https://nshipster.com/key-value-observing/). > Print which [context](https://gist.github.com/ddribin/5158614#comment-798104) is passed to `observeValueForKeyPath:ofObject:change:context:` in lldb. > Say you have declared a context like this: ```objc static const void *MyFooContext = &MyFooContext; ``` > …and you want to know what context it is when you are inside ```objc - (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context ``` > You can do this: ``` (lldb) image lookup -a `context` Address: MyApp[0x00026258] (MyApp.__DATA.__data + 4) Summary: MyFooContext ``` --- ## Creating a KeyPath from Selectors On the subject of Key-Value Coding, [Pitiphong Phongpattranont](https://github.com/pitiphong-p) offers this useful function that builds a keypath from a variable list of selectors: ```objc inline NSString * PTPKeyPathForSelectors(SEL selector, ...) { if (!selector) { return nil; } NSMutableArray *selectors = [NSMutableArray array]; va_list args; va_start(args, selector); SEL arg = selector; do { [selectors addObject:NSStringFromSelector(arg)]; } while((arg = va_arg(args, SEL))); va_end(args); return [selectors componentsJoinedByString:@"."]; } ``` ```objc NSString *keyPath = PTPKeyPathForSelectors(@selector(data), @selector(name), nil); // => @"data.name" ``` ## Nomad CLI Utilities And finally, [Matthew Teece](https://github.com/mteece) gives a shout-out to [Nomad](http://nomad-cli.com/), a world-class collection of command-line utilities—specifically, [Houston](https://github.com/nomad/houston), which can send and manage push notifications from the command line, or within your Ruby application. ```console $ apn push "" -c /path/to/cert.pem -m "Hello!" ``` --- Thus concludes this year’s reader submissions. Thanks again to everyone for your submissions! And thanks to you, dear reader, for sticking with NSHipster for another 52 weeks. Between the [WWDC session](http://asciiwwdc.com/2013/sessions/228?q=NSHipster) and [the book](https://gumroad.com/l/nshipster), 2013 has been a bellwether year for NSHipster. Thank you for your support and enthusiasm for the site—it really does mean the world to me. We have a ton of great stuff planned for 2014, so keep your fixies primed and your artisanal espresso hot for another season of great iOS and OS X knowledge.