Three methods to implement singleton mode in Swift: global variables, internal variables, dispatch_once method
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 singleton: Singleton = Singleton()
}
return
}
}
}
3. dispatch_once method
class Singleton {
class var sharedInstance: Singleton {
get {
struct SingletonStruct {
static var onceToken:dispatch_once_t = 0
static var singleton: Singleton? = nil
}
dispatch_once(&, { () -> Void in
= Singleton()
})
return !
}
}
}
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