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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.
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 rewriten. However, it adds some features of its own that cannot be used in a traditional C program.
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:
These blocks can be nested inside of each other as well, for example:
[[object messageToSendToObject] messageToSendToResultOfInnerMessage];
Interfaces and Implementations
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.
Objective-C has variants that add features to the original Objective C programming language.
Objective-C++ allows for C++ code to be used in Objective-C applications.
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).