Notes on NSUserPreferences

You can set and get NSUserPreferences from any view controller and the app delegate to they are a great way to pass data around the various parts of your iOS App.

Note: NSUserPreferences don’t cross the iOS/watchOS boundry. iOS and watchOS apps each have their own set of NSUserPreferences.

In the example below you have a class `Bool` property that you want to track between user sessions.

// inside some view controller class

var showAll = true

// inside viewDidLoad()

      if let savedShowAll = NSUserDefaults.standardUserDefaults().objectForKey("savedShowAll") {
          showAllStops = savedShowAllS as! Bool
      }

// inside your action assocated a switch control

        showAll = !showAll
        NSUserDefaults.standardUserDefaults().setObject(showAll, forKey: "savedShowAll")

In the code above…
– The var showAll is the data model for a switch object value
– The string savedShowAll is the key for the stored  value
– Use NSUserDefaults.standardUserDefaults().objectForKey() to access a stored value
– Use the if let idiom as the stored value  might not exist
– Use NSUserDefaults.standardUserDefaults().setObject() to save  the value
– Apparently setObject() never fails! 😀