Key-value observing is a mechanism that allows objects to be notified of changes to specified properties of other objects.
In order to understand key-value observing, you should first read Key-Value Coding Programming Guide.
These concepts are covered in this programming topic:
“What is Key-Value Observing?” provides an overview of the functionality provided by key-value observing.
“Registering for Key-Value Observing” describes how to register and receive observation notifications.
“Automatic Versus Manual Support” describes the difference between automatic and manual key-value observing, and how to implement both.
“Registering Dependent Keys” explains how to specify that the value of a key is dependent on the value of another key.
“Ensuring KVO Compliance” describes what your classes must implement to be key-value observing compliant.
“Key-Value Observing Implementation Details ” describes how key-value observing is implemented.
Last updated: 2009-08-14