Hands-On Design Patterns with Swift

Ambient Context

The final pattern, Ambient Context, is similar to the Singleton.

We still have a single instance as a static variable, but the class has multiple subclasses with different behaviors, and each static variable is writeable with a static function:

class Analytics {    static private(set) var instance: Analytics = NoAnalytics()    static func setAnaylics(analitics: Analytics) {        self.instance = analitics    }    func track(event: Event) {        fatalError("Implement in a subclass")    }}class NoAnalytics: Analytics {    override func track(event: Event) {}}class GoogleAnalytics: Analytics {    override func track(event: Event) {        //...    }}class AdobeAnalytics: Analytics {    override func track(event: Event) {        //...    }}struct Event {    //...}

This pattern should ...