Question

I am new to the iPhone / Mac space and this is probably a pretty basic question, I have done some searching and have not found the direct answer.

I would like to know if the addObject method for Arrays / Mutable Arrays does a shallow (pointer only) or deep (copies object) when adding.

1. A mutable array that has been alloc
2. A NSString that has been alloc with some sort of init
3. We addObject the string to the mutable array
4. We then release the NSString

If this is the proper way to do things, that it is assumed that the addObject will do a deep copy of the NSString. Just confirming that this is the proper way to do memory management with mutable array …

Answer 1

addObject: does a shallow copy. What you’re missing is that NSMutableArray retains the object, so it does not go away, but does not require a deep copy. This is a key point to Objective-C memory management. You should read the Memory Management Programming Guide. Cocoa memory management is not complicated, and is incredibly consistent. I have a shortened summary at Three Magic Words.