Facade

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A Facade provides a unified, high-level interface to subsystem interfaces. This allows for simpler, safer access to the more general facilities of a subsystem.

The following is an example of a Facade used to set and retrieve objects in UserDefaults.

enum Defaults {

    static func set(_ object: Any, forKey defaultName: String) {
        let defaults: UserDefaults = UserDefaults.standard
        defaults.set(object, forKey:defaultName)
        defaults.synchronize()
    }

    static func object(forKey key: String) -> AnyObject! {
        let defaults: UserDefaults = UserDefaults.standard
        return defaults.object(forKey: key) as AnyObject!
    }

}

Usage might look like the following.

Defaults.set("Beyond all recognition.", forKey:"fooBar")
Defaults.object(forKey: "fooBar")

The complexities of accessing the shared instance and synchronizing UserDefaults are hidden from the client, and this interface can be accessed from anywhere in the program.

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