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How do I declare an array as a constant in Objective-c?

Answer 1

+1 A:

Griffo 2010-03-12 23:13:29

Answer 2

+2 A:

Instances of NSArray are immutable in Objective-C, so there's no need to use the const qualifier. In fact, you would have to create an instance of NSMutableArray if you did want to be able to modify the array.

jlehr 2010-03-12 23:13:36

Thanks, that makes sense. But if I remove the `const` qualifier i still get the `initializer element is not constant`. I'm sure I'm just missing something in syntax?

Andrew 2010-03-13 00:10:19

Oops, didn't read your initial posting carefully. As bbum point out, objects can only be created dynamically (i.e., allocated on the heap), so we can't initialize a static variable of type NSArray. However, if all you need is an array of NSString instances, you can statically initialize a C array of strings like this: static const NSString *strings[] = { @"foo", @"bar", @"baz" };And then later use it to initialize an NSArray like so: NSString *myStrings = [NSArray arrayWithObjects:strings count:3];as bbum suggests, in a class method.

jlehr 2010-03-13 01:02:47

Answer 3

+3 A:

In short, you can't. Objective-C objects are, with the exception of NSString constants, only ever created at runtime and, thus, you can't use an expression to initialize them.

There are a handful of approaches.

(1) Declare NSArray *testArray without the const keyword and then have a bit of code that sets up the value that is invoked very early during application lifecycle.

(2) Declare a class method on some convenient class method that returns the array, then use a static NSArray *myArray within that method and treat it as a singleton (search SO for "objective-c singleton" for about a zillion answers on how to instantiate).

bbum 2010-03-13 00:29:13

Answer 4

A:

[NSArray arrayWithObjects:  @"foo", @"bar"];

should be

[NSArray arrayWithObjects:  @"foo", @"bar", nil];

guga 2010-07-22 08:44:56

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How do I declare an array as a constant in Objective-c?

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