Instance Method


Raises an exception.


func addObserver(_ observer: NSObject, forKeyPath keyPath: String, options: NSKeyValueObservingOptions = [], context: UnsafeMutableRawPointer?)



The object to register for KVO notifications. The observer must implement the key-value observing method observeValue(forKeyPath:of:change:context:).


The key path, relative to the set, of the property to observe. This value must not be nil.


A combination of the NSKeyValueObservingOptions values that specifies what is included in observation notifications. For possible values, see NSKeyValueObservingOptions.


Arbitrary data that is passed to observer in observeValue(forKeyPath:of:change:context:).


NSSet objects are not observable, so this method raises an exception when invoked on an NSSet object. Instead of observing a set, observe the unordered to-many relationship for which the set is the collection of related objects.

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