Class properties

For historical reasons, the Foundation framework contains many cases where the state of a property is closely associated with the type. Therefore, you will find lots of class properties on Objective-C types. New for the Swift 3 release, we get a tweak to Objective-C that allows us to use a new syntax for creating class properties. These class properties in Objective-C will be imported into Swift as class properties as well.

In Objective-C (old way):

@interface NSCharacterSet  
+ (NSCharacterSet *)controlCharacterSet; 
+ (NSCharacterSet *)whitespaceCharacterSet; 
+ (NSCharacterSet *)whitespaceAndNewlineCharacterSet; 
@end 

In Objective-C (new way):

@interface NSCharacterSet  
@property(class, readonly, strong) controlCharacterSet; 
@property(class, readonly, strong) whitespaceCharacterSet; 
@property(class, readonly, strong) whitespaceAndNewlineCharacterSet; 
@end 

In Swift 2.2:

class NSCharacterSet{ 
 class func controlCharacters...