swift单例的实现

   static func shareInstance() -> ADAlertControllerPriorityQueue {
       struct Static {
           // Singleton instance. Initializing keyboard manger.
           static let shareInstance: ADAlertControllerPriorityQueue = ADAlertControllerPriorityQueue()
       }
       return Static.shareInstance
   }

swift实现单例的四种方式

https://www.jianshu.com/p/230cc900948c