Array with arrays, memory issue

Question

How could I create the following array without having memory leaks:

It should be an array with arrays inside

 arr = [[NSMutableArray alloc] initWithObjects:
                [[NSMutableArray alloc] init], 
                [[NSMutableArray alloc] init],    
                [[NSMutableArray alloc] init],
                [[NSMutableArray alloc] init],     
                [[NSMutableArray alloc] init], 
                [[NSMutableArray alloc] init],     
                [[NSMutableArray alloc] init], nil];

Use [NSMutableArray array] rather than your alloc/init approach. — Hot Licks
– Hot Licks, Commented Feb 8, 2012 at 16:33

Richard J. Ross III · Accepted Answer · 2012-02-08 16:37:45Z

3

Use [NSMutableArray array] instead, which creates an autoreleased object that you don't have to worry about:

arr = [NSMutableArray arrayWithObjects:
            [NSMutableArray array], 
            [NSMutableArray array],    
            [NSMutableArray array],
            [NSMutableArray array],     
            [NSMutableArray array], 
            [NSMutableArray array],     
            [NSMutableArray array], nil];

Note that you must retain / release arr if you want to hold onto it. If what you really want is simply arrays of arrays, I have a class called RJGrid which will do this for you, and is faster than multiple NSMutableArrays (linked lists are slow for lookups).

You can download the class here, in my dropbox. It uses ARC, but is simple enough to convert to a reference counted environment, if you want me to do that.

answered Feb 8, 2012 at 16:37

Richard J. Ross III

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Comments

Jeff Kelley · Accepted Answer · 2012-02-08 16:32:27Z

1

If you’re using ARC, you don’t need to do anything. If you aren’t using ARC, then you can autorelease the arrays:

arr = [[NSMutableArray alloc] initWithObjects:
                [[[NSMutableArray alloc] init] autorelease], 
                [[[NSMutableArray alloc] init] autorelease],    
                [[[NSMutableArray alloc] init] autorelease],
                [[[NSMutableArray alloc] init] autorelease],     
                [[[NSMutableArray alloc] init] autorelease], 
                [[[NSMutableArray alloc] init] autorelease],     
                [[[NSMutableArray alloc] init] autorelease], nil];

answered Feb 8, 2012 at 16:32

Jeff Kelley

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4 Comments

Hot Licks Over a year ago

[NSMutableArray array] is about half as many keystrokes, and easier to read/understand.

Jason Down Over a year ago

Is there some way to use an NSAutorelasePool to simplify it? (No idea... I'm a Objective-C newb with about 10 days of experience).

Richard J. Ross III Over a year ago

@JasonDown no, you'd need to have ARC enabled. I honestly would recommend you learn manual reference counting first, however.

Jason Down Over a year ago

ARC is where the reference counting is handled for you right? (Gives you compile errors if you try to use [release xxx] and things like [super dealloc])

Paul Nikonowicz · Accepted Answer · 2012-02-08 16:34:41Z

1

Use an autorelease memory pool and release the pool when you are done with your arr variable.

http://www.alphero.com/mobile-development/understanding-objective-c-autorelease-memory-management/

answered Feb 8, 2012 at 16:34

Paul Nikonowicz

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