Why subclass NSObject?

Question

What is the purpose/use of NSObject in Objective-C? I see classes that extend NSObject like this:

@interface Fraction : NSObject 

In C++ or

Answer 1

NSObject is the root class of all classes. In my estimation, it's 3 most basic functions are to allocate and initialize memory for you (alloc & init), as well as provide a description function.

Objective-C is all about objects sending messages to other objects -- so NSObject exists to provide that basic functionality.

If this sounds strange to you, you may wish to read more about programming paradigms, particularly object-oriented programming....In a nutshell, however, Objective C is a simple extension to the C language. C gets you the ability to program computer memory, numbers, and characters, but do anything else (like use strings, or show views, for example) you need the extension part, and NSObject is the beginning of that extension.

It may be a useful exercise to pick a class (like NSString, or any for that matter), and follow it's superclasses back to NSObject, to see what functionality each class added.

Hope that helps...