What is the difference between category and extension in Objective-C?
Categories are an Objective-C language feature that let you add new methods to an existing class, much like C# extensions. Objective-C’s extensions are a special case of categories that let you define methods that must be declared in the main implementation block.
What is Objective-C extension?
Objective-C source code ‘messaging/implementation’ program files usually have . m filename extensions, while Objective-C ‘header/interface’ files have . h extensions, the same as C header files. Objective-C++ files are denoted with a . mm file extension.
How do you add a category in Objective-C?
Objective-C Language Categories Create a Category on XCode Open your XCode project, click on File -> New -> File and choose Objective-C file , click Next enter your category name say “CustomFont” choose file type as Category and Class as UIFont then Click “Next” followed by “Create.”
What can be achieved with category and extension?
A category allows you to add methods to an existing class—even to one for which you do not have the source. Categories are a powerful feature that allows you to extend the functionality of existing classes without subclassing.
What are categories used for in C?
Categories provide the ability to add functionality to an object without subclassing or changing the actual object. A handy tool, they are often used to add methods to existing classes, such as NSString or your own custom objects.
What is extension M?
An M file is a text file used by MATLAB, an application used for mathematical computations. It can store a script, class, or an individual function in the MATLAB language. M files are used for executing algorithms, plotting graphs, and performing other mathematical operations.
What is 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. Objective-C runtime library support functions are implemented in the shared library found at /usr/lib/libobjc.
What is ID in Obj C?
id is the generic object pointer, an Objective-C type representing “any object”. An instance of any Objective-C class can be stored in an id variable. An id and any other class type can be assigned back and forth without casting: It also means that a method or function parameter typed as id can accept any object.
Can a class extension be added to a class in Objective C?
Objective-C Extensions. A class extension bears some similarity to a category, but it can only be added to a class for which you have the source code at compile time (the class is compiled at the same time as the class extension).
Can a class extension be declared in the implementation block?
The methods declared by a class extension are implemented in the implementation block for the original class, so you can’t, for example, declare a class extension on a framework class, such as a Cocoa or Cocoa Touch class like NSString. Extensions are actually categories without the category name.
Can a class extension be added at compile time?
A class extension bears some similarity to a category, but it can only be added to a class for which you have the source code at compile time (the class is compiled at the same time as the class extension).