Create an array of integers property in Objective-C

Question

I'm having troubles creating a property of an array of integers in Objective-C. I'm not sure whether this is even possible to do in Obj-C so I'm hoping someone can help me in finding out either how to do it correctly or provide an alternative solution.

myclass.h

@interface myClass : NSObject {  @private int doubleDigits[10]; }  @property int doubleDigits; @end 

myclass.m

@implementation myClass      @synthesize doubleDigits;     -(id) init {          self = [super init];          int doubleDigits[10] = {1,2,3,4,5,6,7,8,9,10};          return self;     }      @end 

When I build and run, I get the following error:

error: type of property 'doubleDigits' does not match type of ivar 'doubleDigits'

Answer 1

This should work:

@interface MyClass {     int _doubleDigits[10];  }  @property(readonly) int *doubleDigits;  @end  @implementation MyClass  - (int *)doubleDigits {     return _doubleDigits; }  @end 

Answer 2

C arrays are not one of the supported data types for properties. See "The Objective-C Programming Language" in Xcode documentation, in the Declared Properties page:

Supported Types

You can declare a property for any Objective-C class, Core Foundation data type, or “plain old data” (POD) type (see C++ Language Note: POD Types). For constraints on using Core Foundation types, however, see “Core Foundation.”

POD does not include C arrays. See http://www.fnal.gov/docs/working-groups/fpcltf/Pkg/ISOcxx/doc/POD.html

If you need an array, you should use NSArray or NSData.

The workarounds, as I see it, are like using (void *) to circumvent type checking. You can do it, but it makes your code less maintainable.