Standard C Arrays in Singletons

Question

I'm trying to incorporate a standard C-array of floats into a singleton so that it can be accessed globally. Is this even possible? I feel the problem lies with the creation of the array; because It will not let me simply produce an array in the same way as I would in a header file.

For example:

@interface globalVariables : NSObject{

    float hzArray[4]; //arrays of floating point variables.

}

@property(nonatomic) float hzArray[4]; //ERROR RETURNED HERE

+(globalVariables *) getVariable;

@end

returns the error:

Property cannot have array or function type 'float[4]'

I realise this is probably a very rudimentary question, but I appreciate any advice you can give me.

Thanks, Tom.

It seems the issue comes from the use of your property. I am not fully sure, but I don't think you can mix c and objc properties/variables. Try making the float array a const float hzArray[4]; and see if that works. — user2277872, Jul 09 '14 at 15:10
http://stackoverflow.com/questions/476843/create-an-array-of-integers-property-in-objective-c — Larme, Jul 09 '14 at 15:15
A "singleton" is simply an API that returns the pointer to something. The "something" can be anything you want. — Hot Licks, Jul 09 '14 at 15:17
@property(nonatomic) float *hzArray; will work, but you'll need to make the malloc and free calls yourself — robert, Jul 09 '14 at 15:21
Larme, thanks for the link, it appears C Arrays are not supported data types for properties. I'll work on adjusting my program to work with NSArray. Thanks, Tom. — Tom Wilson, Jul 09 '14 at 15:38

score 0 · Accepted Answer · edited May 23 '17 at 11:50

Before you read on, check out the question that Larme linked.

Done? Ok. The short answer here is that you can't easily have arrays as properties in Objective-C, and you probably don't want to anyways. To do what you seem to want, I strongly recommend you use an NSArray, as some of the other commenters have mentioned, and store your float values in it, wrapped in NSNumber objects. Something like:

@interface GlobalVariables : NSObject
@property (strong, nonatomic) NSArray *hzArray;
+ (GlobalVariables *)getVariable;
@end

@implementation GlobalVariables
+ (GlobalVariables *)getVariable {
    GlobalVariables *gv = [[self alloc] init];
    // init the array in some meaningful way
    gv.hzArray = @[@(1), @(2), @(3)];
    return gv;
}
@end

^{Note that I've renamed the class to GlobalVariables, with a capitalized first letter, because that's the convention for class names in Objective-C.}

In theory one could use an NSValue property containing an array pointer. Of course, there is no need to use properties to implement a singleton anyway. — Hot Licks, Jul 09 '14 at 18:13
Thank you very much for your advise, i've managed to get this integrated into my program. — Tom Wilson, Jul 10 '14 at 14:13

Standard C Arrays in Singletons

1 Answers1