Should I always check if [[NSArray alloc] init…] returns nil?

Question

Should I always check if [[NSArray alloc] init…] (or with any other collection class) returns nil? The Apple docs say that objects may return nil if allocation or initialisation fails. I don't know when initialising may fail with NSArray, but I guess that allocation may fail with insufficient memory. And because I'm developing for iOS, that may become a regular problem. Do I have to about that and check every time I want to create a new array, or will my app fail because of memory constraints (assuming worst-case situation, of course) and checking for nil is just a waste of cycles?

Currently, I'm only checking when I allocate a mutable collection with a large predetermined capacity (e.g. [NSMutableArray arrayWithCapacity: 1000]) or an immutable collection with lots of objects (over a thousand).

Thank you.

Richard J. Ross III · Accepted Answer · 2012-02-27 16:29:31Z

2

No, not with NSArray. NSArray is a linked list using structs, so it does not malloc much behind the scenes. Checking for nil, at least with NSArray is rather pointless.

However, if you were using a collection class like CCArray, from cocos2d, for example then checking for nil with a large array could be beneficial.

Still, the size of a pointer on iOS is 8 bytes, and even a C-Array of 1000 elements is only 8 KB of RAM. In most cases, you won't be using enough memory to the point where you will run out.

Also note that if you come to the point where your application is running low on memory, there are many delegate methods that you can register to to be warned about this and fix it.

edited Feb 27, 2012 at 16:29

answered Feb 26, 2012 at 15:48

Richard J. Ross III

55.7k25 gold badges139 silver badges205 bronze badges

Sign up to request clarification or add additional context in comments.

13 Comments

Constantino Tsarouhas Over a year ago

@jrturton I think you meant to comment on my question. Yes, I realise now how pointless it is, but I think my intentions are nevertheless clear. I edited the question. :-p

Peter Hosey Over a year ago

NSArray is an object class (actually a cluster of classes behind the scenes). An array may be backed by a linked list, or it may be backed by a C array or some other collection—it's an implementation detail that's deliberately hidden from you.

Rob Keniger Over a year ago

1000 8-byte elements is 8 kilobytes, not 8 megabytes.

Richard J. Ross III Over a year ago

@H2CO3 [NSArray new] is pointless because NSArray is immutable. It cannot be changed, so its just an empty array, which is better described by nil.

Jonathan Grynspan Over a year ago

@RichardJ.RossIII: an empty set is not the same as a null pointer. There are legitimate situations where one needs to distinguish (e.g. "valid-but-empty data" vs. "invalid data.")

|

Collectives™ on Stack Overflow

Should I always check if [[NSArray alloc] init…] returns nil?

1 Answer 1

13 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

13 Comments

Your Answer

Sign up or log in

Post as a guest

Related