三种Swift实现单例模式的方法:全局变量,内部变量,dispatch_once方式
1. 全局变量
private let _singleton = Singleton() class Singleton: NSObject { class var sharedInstance: Singleton { get { return _singleton } } }
2. 内部变量
class Singleton { class var sharedInstance: Singleton { get { struct SingletonStruct { static let singleton: Singleton = Singleton() } return SingletonStruct.singleton } } }
3. dispatch_once方式
class Singleton { class var sharedInstance: Singleton { get { struct SingletonStruct { static var onceToken:dispatch_once_t = 0 static var singleton: Singleton? = nil } dispatch_once(&SingletonStruct.onceToken, { () -> Void in SingletonStruct.singleton = Singleton() }) return SingletonStruct.singleton! } } }