What's the best way to use Obj-C 2.0 Properties with mutable objects, such as NSMutableArray?

Question

I have an Obj-C 2.0 class that has an NSMutableArray property. If I use the following code, then the synthesised setter will give me an immutable copy, not a mutable one:

Answer 1

It's not common to pass around NSMutableArrays in Cocoa. Standard Cocoa practice would be to implement the key-value coding compliant methods for an indexed to-many property. This has two benefits:

1. Key-value observing works as expected (there are several cases where observing an NSMutableArray leads to not-what-you-want behavior)
2. The implementation of your data structure is hidden because you expose mutating methods (e.g. -[MyObject insertObjectInMyProperty:(id)newObject atIndex:(NSUInteger)i] , not the data structure itself.