How to copy a NSMutableArray

Question

I would simply like to know how to copy a NSMutableArray so that when I change the array, my reference to it doesn't change. How can I copy an array?

Solution

There are multiple ways to do so:

NSArray *newArray = [NSMutableArray arrayWithArray:oldArray];

NSArray *newArray = [[[NSMutableArray alloc] initWithArray:oldArray] autorelease];

NSArray *newArray = [[oldArray mutableCopy] autorelease];

These will all create shallow copies, though.

(Edit: If you're working with ARC, just delete the calls to autorelease.)

For deep copies use this instead:

NSMutableArray *newArray = [[[NSMutableArray alloc] initWithArray:oldArray copyItems:YES] autorelease];

Worth noting: For obvious reasons the latter will require all your array's element objects to implement NSCopying.

Comments

[Supertecnoboff]

What do you mean by shallow and deep copies??

[Regexident]

@Supertecnoboff: developer.apple.com/library/mac/documentation/Cocoa/Conceptu‌​al/…

[Supertecnoboff]

Thanks, very interesting. I never knew about this concepts.

[Max Strater]

A shallow copy is a new array that contains references to the same elements, a deep copy is a new array that contains copies of each element. If you made a shallow copy and then changed one of the elements in the original array, the shallow copy would also show this change. If it was a deep copy it would not.

[Matthew Ferguson]

[sourceArray mutableCopy] with iOS 10 is working great