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August 29, 2015 14:27
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Thread safe shared instance "singletons" in Swift.
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| class Singleton { | |
| class var sharedInstance: Singleton { | |
| struct Static { | |
| static var token: dispatch_once_t = 0 | |
| static var instance: Singleton! | |
| } | |
| dispatch_once(&Static.token) { | |
| Static.instance = Singleton() | |
| } | |
| return Static.instance | |
| } | |
| init() { | |
| println("Init the Singleton!") | |
| } | |
| } | |
| // | |
| // UPDATE | |
| // | |
| // Static variables in a struct are lazily initialized, so there's no need for the dispatch once. | |
| class Singleton { | |
| class var sharedInstance: Singleton { | |
| struct Static { | |
| static let instance: Singleton! = Singleton() | |
| } | |
| return Static.instance | |
| } | |
| init() { | |
| println("Init the Singleton!") | |
| } | |
| } | |
| // Alternatively, a global variable, which is also lazily initialized, could be used to store the shared instance. | |
| // A class method could optionally be added to provide a more object-oriented access to the shared instance. | |
| let SingletoneSharedInstance: Singleton = Singleton() | |
| class Singleton { | |
| class var sharedInstance: Singleton { | |
| return SingletoneSharedInstance | |
| } | |
| init() { | |
| println("Init the Singleton!") | |
| } | |
| } |
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