Question

What happens if I call [alloc] init] on an object which already was initialized and alloc’ed?

In my particular case I have an NSMutableArray which I initialize in superclass Parent using NSMutableArray* someArray = [NSMutableArray alloc] init];

In subclass Child I need to insert an object in someArray but at a specific index, for example 3.
So if the array has no items, or if it has less items than the index I’m trying to insert at (array has 4 items, and I want to insert at index 10) it will crash.

What would happen if I initialized someArray again in Child class? Would the pointer stored in someArray be replaced with the new one I’m initializing and the “old” one would just leak?

EDIT:

Sorry, my terminology was a bit off. I don’t mean doing [someObject alloc], but doing someObject = [SomeClass alloc] init]; where someObject had previoulsy been initialized with an instance of SomeClass

Answer 1

Just for clarity when you say “What happens if I call [alloc] init] on an object…” your terminology is wrong.

The following line:

NSMutableArray* someArray = [[NSMutableArray alloc] init];

Reads in English:

“Send the alloc message to the NSMutableArray class object, then send the init message to the object returned from the first message, then store the object returned from init into the pointer variable named someArray.”

I say that to emphasize the fact that you’re not “calling alloc/init” on an existing object, you’re making a new object, and storing a reference to this new object over the reference you had to the previous object. Since you no longer have a reference to that previous object, you’ve lost the ability to properly release its memory, so yes, you’ll leak it.