Approach B: nested struct
class SingletonB {
class var sharedInstance: SingletonB {
struct Static {
static let instance: SingletonB = SingletonB()
}
return Static.instance
}
}
Approach C: dispatch_once
class SingletonC {
class var sharedInstance: SingletonC {
struct Static {
static var oncetoken: dispatch_once_t = 0
static var instance: SingletonC? = nil
}
dispatch_once(&Static.oncetoken) {
Static.instance = SingletonC()
}
return Static.instance!
}
}