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Retrieving information from the `change` dictionary from KVO

Method

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
}

has a parameter change

, which is a dictionary, which contains information about the nature of the change in value, how would you know what was in this dictionary?

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Here is a list of the keys used in the change dictionary .

Excerpt:



Keys used by the shift dictionary

These constants are used as keys in the change dictionary passed to observeValueForKeyPath:ofObject:change:context:

.

NSString *const NSKeyValueChangeKindKey;
NSString *const NSKeyValueChangeNewKey;
NSString *const NSKeyValueChangeOldKey;
NSString *const NSKeyValueChangeIndexesKey;
NSString *const NSKeyValueChangeNotificationIsPriorKey;
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