Open Radar

 
Summary:

In iOS, the desired behavior for most properties is nonatomic; because atomic is the default for Objective-C, iOS projects end up littered with `nonatomic` annotations which clutters our interfaces with what are really implementation details. For compatibility reasons, the default atomicity for properties is unlikely to be changed.

I propose a new series of keywords to specify atomicity for multiple properties, after the manner of how @required and @optional specify requiredness for multiple methods in protocols. So, the current state of affairs leads to interfaces like the following:

    @interface StrawManController : UIViewController
    @property (strong, nonatomic) IBOutlet UILabel *titleLabel;
    @property (strong, nonatomic) IBOutlet UILabel *descriptionLabel;
    @property (strong, nonatomic) IBOutlet UIImageView *pictureView;
    @property (strong, nonatomic) IBOutlet UIButton *explosionButton;
    @property (weak, nonatomic) id <StrawManDelegate> delegate;
    @property (weak, nonatomic) id <StrawManDataSource> dataSource;
    @property (copy) NSString *someAtomicProperty;
    @property BOOL anotherAtomicProperty;
    @end
    
This interface could be simplified by the addition of keywords @nonatomic and @atomic. In the absense of any annotation to the contrary, atomic remains the default:

    @interface StrawManController : UIViewController
    @nonatomic
    @property (strong) IBOutlet UILabel *titleLabel;
    @property (strong) IBOutlet UILabel *descriptionLabel;
    @property (strong) IBOutlet UIImageView *pictureView;
    @property (strong) IBOutlet UIButton *explosionButton;
    @property (weak) id <StrawManDelegate> delegate;
    @property (weak) id <StrawManDataSource> dataSource;
    
    @atomic
    @property (copy) NSString *someAtomicProperty;
    @property BOOL anotherAtomicProperty;
    @end
    
The old property modifiers `atomic` and `nonatomic` should take precedence over the currently scoped default atomicity.