Swift's single-case mode

Three ways to implement Singleton mode in Swift: global variables, internal variables, dispatch_once methods

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!          }}}  

　　

Swift's single-case mode