Returning an NSArray without Leaking?

Question

I have been struggling with the best pattern for returning an array from a static method.

In my static method getList (in the BIUtility Class), I am allocating an NSArray to return. in the return line, I do:

return [array autorelease];

Then in the calling method, I am allocating an array like this:

NSArray * list = [[[NSArray alloc] initWithArray:[BIUtility getList]] retain];

Later I release the list using:

[list release];

I think this is causing a memory leak as the retain is increasing the retain count one too many. However, if I do not do the retain, I get a Bad_Exec because it has already freed the class.

I feel like I am overthinking this and there must be a typical pattern. I have been looking all over the place and I cannot find a "best practice".

I appreciate your help.

Answer 1

You should replace:

NSArray * list = [[[NSArray alloc] initWithArray:[BIUtility getList]] retain];

With:

NSArray * list = [[BIUtility getList] retain];

This is because getList actually returns a pointer to the NSArray.

If it were a mutable array, however, you should say [[BIUtility getList] copy]; so that you don't accidentally mutate an array that another object has a reference to.

If you are curious, you were getting a memory leak because your original statement increments two counters, while you only release one later.

These parts of the statement increase counts:

 [anObject]] retain]
 [anClassname alloc]

[anObject copy] will also create an object with a count of 1.