A method that takes both NSArray and NSMutableArray

Question

I want to create a method that can take an NSMutableArray or an NSArray object.

I think I can just use (id) as the parameter type... or convert the NSArray to NSMutableArray before passing. However I'm not really happy with these solutions.

In other languages I might pass an IList or some shared object that they both inherit from...

I need to enumerate through the array in my method.

What is the way people would typically do this in objective c?

Answer 1

Take NSArray. NSMutableArray derives from NSArray, so as long as you're only using the NSArray members (such as read-only enumeration), you'll be safe.

Relevant documentation (from Apple's developer site):

• NSMutableArray class reference
• NSArray class reference

Answer 2

Use NSArray* -- NSMutableArray inherits from it and you can iterate both as if they were NSArrays.

Answer 3

Since NSMutableArray is a subclass of NSArray, just have your method take an NSArray parameter. That way, it will take anything that is or is a subclass of NSArray.

Answer 4

I would stick with NSArray as the parameter because I prefer to use immutable objects wherever possible (looser coupling), and then use the -mutableCopy method when required to send them to an to a function that needs to modify the array.