Objective-C was the first programming language by Apple to support mobile applications on its platform. It’s an OO (object-oriented) language that uses syntax from C and the OO aspects of SmallTalk.

Includes knowledge areas


Categories provide the ability to add functionality to an object without subclassing or changing the actual object.


Objective-C properties offer a way to define the information that a class is intended to encapsulate.


Blocks are a language-level feature, which allow to create distinct segments of code that can be passed around to methods or functions as if they were values. Blocks are Objective-C objects, which means they can be added to collections like NSArray or NSDictionary.


Key-value observing provides a mechanism that allows objects to be notified of changes to specific properties of other objects.


Most collections in Objective-C code are instances of one of the Cocoa and Cocoa Touch collection classes, like NSArray, NSSet and NSDictionary.

Object comparison / copying / encoding & decoding

Object comparison refers to the ability of an object to determine whether it is essentially the same as another object. Copying an object creates a new object with the same class and properties as the original object. To support encoding and decoding of instances, a class must adopt the NSCoding protocol and implement its methods. This protocol declares two methods that are sent to the objects being encoded or decoded.


Objective-C allows you to define protocols, which declare the methods expected to be used for a particular situation.

Exception Handling

The exception handling mechanisms available to Objective-C programs are effective ways of dealing with exceptional conditions. They decouple the detection and handling of these conditions and automate the propagation of the exception from the point of detection to the point of handling.

Objective-C Runtime

The Objective-C runtime is a runtime library that provides support for the dynamic properties of the Objective-C language, and as such is linked to by all Objective-C apps.


Key-value coding is a mechanism enabled by the NSKeyValueCoding informal protocol that objects adopt to provide indirect access to their properties.

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