Peter Steinberger • 4/5/2012

Don't Call willChangeValueForKey Unless It's Really Needed

This technical article clarifies the common misconception that manually calling willChangeValueForKey: and didChangeValueForKey: is always necessary for Key-Value Observing (KVO) in Objective-C. It explains that using standard setter methods typically triggers automatic notifications. The article details the specific cases where manual calls are required, such as when a property's value depends on other variables (using NSOperation's state properties as an example) or when subclassing certain Cocoa classes.

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#Io #Objective C #Kvo