IBOutlets strong or weak [duplicate]

Question

Outlets can be created like this

@interface SearchViewController : UIViewController<UISearchBarDelegate> {    
    IBOutlet UIView *viewSearchBar;
    IBOutlet UIScrollView *scrollVieww;
    IBOutlet UILabel *lblName;
}

and also like this

@interface SearchViewController : UIViewController<UISearchBarDelegate> {

}

@property(nonatomic, weak) IBOutlet UIScrollView *scrollVieww;
@property(nonatomic, weak) IBOutlet UIView *viewSearchBar;
@property(nonatomic, weak) IBOutlet UILabel *lblName;

@end

I know the nonatomic/atomic strong/weak in ARC, but in the first example what are they? strong, weak, nonatomic or atomic.

Please explain or link me to some detail.

Answer 1

Instance variables under ARC are strong by default. And they are neither atomic nor nonatomic, since they are just instance variables and not accessor methods. The atomic/nonatomic flags are related to multi threading. They specify whether or not the accessor methods should be atomic. When an accessor is atomic, the execution can't change to an other thread in the middle of the accessor method. When it's nonatomic, there is no such restriction.

Note: IBOutlet is a typedef of nothing. It's just a flag for Interface Builder and has no memory related functions.

Answer 2

Variables are __strong by default under ARC so:

IBOutlet UIView *viewSearchBar;

is the same as

IBOutlet __strong UIView *viewSearchBar;

With regard to the recommended way to deal with IBOutlets under ARC see: the answer to this