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Objective-C is an object-oriented programming language used to make computer programs for macOS and iOS devices.

History[change | change source]

Objective-C was created in the early 1980s by two programmers named Brad Cox and Tom Love. It didn't become popular, however, until it was bought by NeXT in 1988 for their NeXTSTEP operating system. After NeXT was bought by Apple in 1996, it became the main programming language for Mac OS X and later the iPhone, iPod touch and iPad.

Basics[change | change source]

Objective-C is a strict superset of C, meaning that any code that can be written in C can be used in Objective-C programs without being rewritten. However, it adds some features of its own that cannot be used in a traditional C program.

Messages[change | change source]

In Objective-C, functions are called using messages, a feature inspired by the SmallTalk programming language. Messages look like "blocks" of code similar to the on shown below:

[object messageToObject];

These blocks can be nested inside of each other as well, for example:

[[object messageToSendToObject] messageToSendToResultOfInnerMessage];

Interfaces and Implementations[change | change source]

Unlike other programming languages such as C and Java, Objective-C classes are divided into two separate parts:

  • Interface, which contains the initial declarations of variables and functions.
  • Implementation, which contains the actual code for functions.

Usually, these are put in two different files, with the interface using the ".h" extension and the implementation using the ".m" extension.

Variations[change | change source]

Objective-C has variants that add features to the original Objective C programming language.

Objective-C++[change | change source]

Objective-C++ allows for C++ code to be used in Objective-C applications.

Objective-C 2[change | change source]

Objective-C 2 is an improved version of Objective-C. It adds many features, such as garbage collection (automatic memory management), fast enumeration and properties (the automatic generation of variable methods).