Analyzing the Swift single case pattern _swift by example

Three swift ways to implement a single case pattern: global variables, internal variables, dispatch_once

1. Global variables

Private Let _singleton = Singleton () 
class Singleton:nsobject { 
  class var Sharedinstance:singleton {get 
    {
   return _singleton 
    }}} 
 

2. Internal variables

Class Singleton { 
  class var Sharedinstance:singleton {get 
    { 
      struct) singletonstruct { 
        static let sin Gleton:singleton = Singleton () 
      } return 
       Singletonstruct.singleton 
    } 
  } 
  

3. Dispatch_once mode

Class Singleton { 
  class var Sharedinstance:singleton {get 
    { 
      struct singletonstruct { 
        static var Oncetok en:dispatch_once_t = 0 
        static var Singleton:singleton = nil 
      } 
      dispatch_once (& Singletonstruct.oncetoken, {()-> Void in 
        Singletonstruct.singleton = Singleton () 
      }) 
      return singletonstruct.singleton!}}} 
 

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