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iOS Objective-C Basics (Retired) Advanced Objective-C Dynamic Typing

Eric M
Eric M
2,242 Points
Posted by Eric M
Eric M
2,242 Points

In Objective-C, is the generic `id` type only a generic for Objective-C objects, or any type of object?

In the video, it's emphasized that the generic type id can "point to any class".

However (and this may be an unimportant distinction), it seems more likely to me that it may only point to instances of classes which extend NSObject.

`id` [contains the set of]: NSArray, NSString, NSDictionary

`id` [does not contain]: Native C Array, Native C Object

What do you guys think, is this true?

1 Answer

Andrei Fecioru
Andrei Fecioru
15,059 Points

Yes, you have a good intuition about this. In Objective C the id type defines a pointer to any type, but is unlike void * in vanilla C/C++ in that it always points to an Objective-C object. More specifically, it must point to a an object which inherits the NSObject interface (the object must respond to the retain and release selectors).