Objective-C
{{language|Objective-C |exec=machine |strength=weak |express=explicit |checking=static |parampass=value |gc=allowed |site=http://developer.apple.com/documentation/Cocoa/Conceptual/ObjectiveC/ |LCT=yes}}{{language programming paradigm|Object-oriented}} [[wp:Objective-C|Objective-C]] is an [[object-oriented]] superset of the [[derived from::compatible with::C]] language. It mostly copies the message passing system from [[derived from::Smalltalk]]. It was popularized by NeXT, and then again by [[Apple Inc]] with [[Mac OS X]] and [[iOS]] to implement the [[Cocoa]] frameworks. Its main reference implementation is within the [[gcc]] compiler, maintained mostly by Apple.
As of October 2011, with the release of [http://developer.apple.com/library/ios/#documentation/DeveloperTools/Conceptual/WhatsNewXcode/Articles/xcode_4_2.html#//apple_ref/doc/uid/00200-SW1 XCode 4.2], Apple switched from [[gcc]] to [[wp:Clang|Clang]] as its default compiler. [[wp:Clang|Clang]]/[[wp:LLVM|LLVM]] offers competitive execution times, better compile times, improved error messages, and supports a simpler alternative syntax for expressing NSArray & NSDictionary literals and indexing. In the same release Apple also introduced automatic reference counting (ARC) which eliminates the need to manually release/retain memory. With ARC the compiler reports an error any time it encounters a call to release, autorelease, retain, or dealloc.
The release of Xcode 4.4 (4.5 for iOS) added [http://clang.llvm.org/docs/ObjectiveCLiterals.html syntax to specify literals] for NSArray, NSDictionary, NSNumber, and NSString, as well as subscript syntax to access elements of NSArray and NSDictionary.
Unless otherwise stated, Objective-C code samples will assume that they are compiled with ARC enabled, and that the compiler supports Objective-C literals and Blocks.
For details of how to compile and run examples of Rosetta Code tasks written in Objective C under Linux or Windows see [http://www.gnu.org/software/gnustep/ GNUstep]