This tag should be used only on questions that are about Objective-C features or depend on code in the language. The tags [cocoa] and [cocoa-touch] should be used to ask about Apple's frameworks or classes. Use the related tags [ios], [macos], [apple-watch] and [tvos] for issues specific to those platforms.
Objective-C is an object-oriented programming language combining features of C (c) and Smalltalk (smalltalk). It is a strict superset of C (any valid C code is equally valid Objective-C code, with the minor exception that id is a free identifier for user use in C while it is a keyword in Objective-C), and it inherits its object-oriented capabilities from Smalltalk. All procedural syntax is identical to that of C, and all object-oriented syntax is an implementation of Smalltalk messaging.
Objective-C was created primarily by Brad Cox and Tom Love in the early 1980s at their company Stepstone. It is now primarily developed by Apple, Inc.
Objective-C is a general-purpose, high-level, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. It is the main programming language used by Apple for macos and ios and their respective APIs, cocoa and cocoa-touch.
Objective-C inherits the syntax, primitive types, and flow control statements of C and adds syntax for defining classes and methods. It also adds language-level support for object graph management and object literals while providing dynamic typing and binding, deferring many responsibilities until run time.
Hello World in Objective-C
#import <Foundation/Foundation.h>
int main(void)
{
NSLog(@"Hello World!");
return 0;
}
Syntax
Objective-C is a thin layer on top of C, and moreover is a strict superset of C; it is possible to compile any C program with an Objective-C compiler, and to freely include C code within an Objective-C class. Objective-C derives its object syntax from Smalltalk. All of the syntax for non-object-oriented operations (including primitive variables, pre-processing, expressions, function declarations, and function calls) is identical to that of C, while the syntax for object-oriented features is an implementation of Smalltalk-style messaging.
Objective-C has many powerful features as detailed below:
- Categories Extend Existing Classes.
- Protocols & Delegates
- Blocks
- Dealing with Errors
- Properties with encapsulation
References
- Good resources for learning Objective-C (Stack Overflow post).
- Programming with Objective-C
- Concepts in Objective-C Programming
- Cocoa Memory Management Programming Guide, an essential read, especially the part about Ownership Policy
- Learn Objective-C from Cocoa Dev Central, an introductory tutorial to the language
- Object-Oriented Programming with Objective-C
- WWDC 2012 videos on Modern Objective-C and Migrating to Modern Objective-C
- WWDC 2013 video on Advances in Objective-C
- WWDC 2014 video on Integrating Swift with Objective-C
- Advanced Memory Management Programming Guide
- Learn Objective-C basics from CodeSchool
- Ry’s Objective-C Tutorial
- Objective-C Guide For Developers
- Objective-C Tutorials
- Objective-C Cheat Sheet and Quick Reference
Frequently posted questions in the Objective-C tag
- What's the difference between the atomic and nonatomic attributes?
- How does an underscore in front of a variable in a cocoa objective-c class work?
- Getting date from [NSDate date] off by a few hours
- Objective C Equivalent of PHP's "Variable Variables"
- NSMutableArray addObject not working
- Objective C for Windows
- Objective C NSString* property retain count oddity
- How to add percent sign to NSString
- Passing Data between View Controllers
Books
- Programming in Objective-C
- Effective Objective-C 2.0: 52 Specific Ways to Improve Your iOS and OS X Programs
- Zen and the Art of the Objective-C Craftsmanship
Video Tutorial
- Developing iOS 7 Apps for iPhone and iPad by Stanford University - FREE
From the site, "Tools and APIs required to build applications for the iPhone and iPad platform using the iOS SDK. User interface designs for mobile devices and unique user interactions using multi-touch technologies. Object-oriented design using model-view-controller paradigm, memory management, Objective-C programming language." (Similar courses are also available for iOS 8 & 9, but only in Swift)
