Day 6: Difference between class category and class extension in Objective-C ?
- Factor -> Source code
Categories provide a way to add methods to a class even if its source code is not available to you. ex: NSString
Extensions are only possible if the source code is available , because compiler compiles the extension & source code at same time.
2. Factor ->Instance variable/Properties
Category : Not possible
Extensions : Possible
3. Factor ->Accessibility to Inherited classes.
Category — All methods defined inside a category are also available to the inherited class
Extensions — All properties and methods defined inside a class extension are not even available to inherited class.
Bottom Line
Use category when you need to want to add any methods to a class whose source code is not available to you OR you want to break down a class into several files depending on its functionality.
Use class extensions when you want to add some required methods to your class outside the main interface file. Also when you want to modify a publicly declared variable in the main interface file .
References:
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