Question

I understand that few users have already asked about the error listed in Title line. However, I am a novice in Objective-C programing and I am not able to connect how the responses on other pages answer why I am getting an error for this program.

Thanks!

@interface ClassA:NSObject

{
    int x;
}

-(void)initVar:(int) a;

@end

@implementation ClassA

-(void)initVar:(int) a
{
    x=a;
}

@end

@interface ClassB:ClassA

-(void)printVar;

@end

@implementation ClassB


-(void)printVar
{
    NSLog(@"X = %i", x);
}

ClassA *a= [[ClassA alloc] init]; // shows error: Initializer element is not a compile-
                                  // time constant.
[a initVar:100]; 

@end

Answer 1

Objective-C is a strict superset of C. It’s illegal in C to have any executable code outside of a function (or method in Objective-C).

If your intention is to have a global variable of type ClassA, the best solution (IMHO) is to use a class method to access it. This will also allow you to do your initialisation.

static ClassA *a = nil; // static limits the visibility of a

+ (ClassA*) theA
{
    static dispatch_once_t pred;

    dispatch_once(&pred, 
    ^{
         a = [[ClassA alloc] init];
         [a initVar:100]; 
    });
}

The dispatch_once() call is the currently favoured idiom to ensure the initialisation code only gets executed once and is all done in a thread safe way.

You should choose a different name for your initVar: method. The initprefix is a convention that signifies an object initialisation method (like init).