How to determine when Settings change on iOS

I have created a custo开发者_如何学编程m Settings.app bundle using the standard root.plist approach for the iPhone. I'm wondering if there's a way to determine when the user changes those settings in my app...

You can listen for NSUSerDefaultsDidChange-notifications with this:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(defaultsChanged) name:NSUserDefaultsDidChangeNotification object:nil];

Whenever the NSUserDefaults changes, defaultsChanged will be called.

Don't forget to call [[NSNotificationCenter defaultCenter] removeObserver:self]; when you want to stop listening for these notifications (you should also do this when object gets deallocated).

The syntax is for Swift 2. Using Swift you would do something like this to subscribe to changes for the NSUserDefaults :

NSNotificationCenter.defaultCenter().addObserver(self, selector: "defaultsChanged:", name: NSUserDefaultsDidChangeNotification, object: nil)

Then create the method like this :

func defaultsChanged(notification:NSNotification){
    if let defaults = notification.object as? NSUserDefaults {
       //get the value for key here
    }
}

SWIFT 4

Register observer in viewController,

NotificationCenter.default.addObserver(self, selector: #selector(settingChanged(notification:)), name: UserDefaults.didChangeNotification, object: nil)

Selector implementation

 @objc func settingChanged(notification: NSNotification) {
    if let defaults = notification.object as? UserDefaults {
        if defaults.bool(forKey: "enabled_preference") {
            print("enabled_preference set to ON")
        }
        else {
            print("enabled_preference set to OFF")
        }
    }
}

Register to receive NSUserDefaultsDidChangeNotification notifications. It's not obvious, but the iOS Application Programming Guide describes it as such:

Preferences that your application exposes through the Settings application are changed

An example accessing an app specific Bool type setting with key "instantWeb":

func observeUserDefaults(notification: NSNotification) {
    print("Settings changed")
    if let defaults = notification.object as? NSUserDefaults {
        if defaults.valueForKey("instantWeb") as! Bool==true {
            print("Instant Web ON")
        }
    }
}

Listen to change in settings

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(someMethod:) name:NSUserDefaultsDidChangeNotification object:nil];

Remember to remove the observer, once this view controller is no longer in memory.

In iOS10, try this:

UNUserNotificationCenter.current().getNotificationSettings { (settings) in
    // Your code here
}