Are private variables in Objective-C strong?

Question

So searching around Stack Overflow this seems to be how to make private variables in Objective-C:

@interface ClassName()
{
@private
    NSArray* private;
}
@property (strong, nonatomic) NSArray* public;
@end

Now this is where I get confused. The property is declared as (strong, nonatomic), but the private variable has nothing of the sort. So how does arc know if it's strong or not?

Answer 1

Instance variables are __strong by default.

From Apple's ARC Transition Guide, regarding variables (presumed to include instance variables):

__strong is the default

and later:

With ARC, instance variables are strong references by default—assigning an object to an instance variable directly does extend the lifetime of the object

This holds until the property is connected to the ivar via @synthesize. At this point, the ownership qualifier of the property takes precedence. However, if you declare a property as anything but strong, and then implement both the setters and getters by hand, you'll have to manually declare the backing ivar's ownership qualifier as well.