Analyze the Swift singleton pattern by example
- 2020-05-09 19:23:12
- OfStack
There are three ways that Swift implements the singleton pattern: global, internal, and dispatch_once
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 SingletonStruct.singleton
}
}
}
3. dispatch_once way
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!
}
}
}
That's all for this article, I hope you enjoy it.