Does removeObserver() remove all observers?

Question

Does the following remove all NSNotificationCenter.defaultCenter there were added by name a view?

NotificationCenter.default.removeObserver(self)

If I have the following in the same view of viewDidLoad(), will they be removed with the single line above?

NotificationCenter.default.addObserver(self, selector: Selector(("method1")), name: UITextField.textDidChangeNotification, object: nil)

NotificationCenter.default.addObserver(self, selector: Selector(("method2")), name: UITextView.textDidChangeNotification, object: nil)

Solution 1

Yes, the removeObserver(self) call will remove all observers that you added using addObserver:selector:name:object: with an observer of self, regardless of the notification name, object, or selector you specified.

It is a bad idea to use the removeObserver(self) method anywhere but in your object's deinit method, because some system classes (or subclasses of objects that you define) may have added observers that you don't know about. That method call is a "scorched earth" call the removes ALL observers from the object.

Instead you should call removeObserver:name:object: and remove only the observers that you added.

Solution 2

Removes all the entries specifying a given observer from the receiver’s dispatch table. https://developer.apple.com/library/ios/documentation/Cocoa/Reference/Foundation/Classes/NSNotificationCenter_Class/index.html#//apple_ref/occ/instm/NSNotificationCenter/removeObserver:

So I guess it'll remove all observers only when all are same as specified by the parameter.

Comments

[4thSpace]

I've updated the question. Even though the two observers in the OP have two different method names, the single line of code should remove both right?

[Duncan C]

See my answer to your question. The answer is yes, but don't use it.

[4thSpace]

If I remove these by name, which method should I remove them in? I loaded through viewDidLoad(). I don't get any autocomplete for a deinit.

[4thSpace]

Your answer is vague. What "parameter"?

[Duncan C]

Search for it in the Swift language reference iBook (which is free.) If you add an observer in viewDidLoad (which only gets called once on creation of a view controller) then you need to put the balancing call to removeObserver in a deinit method that you add. Your deinit method will be called right before your object gets deallocated.

[4thSpace]

I've added a deinit to my UIViewController. How do I test this in the simulator? It doesn't trigger with a home button click or app shutdown.

[Duncan C]

I didn't say anything about a parameter. My answer has a timestamp of 2:56.