The Observer design pattern falls under the Behavioral design pattern category and is used when you would want to notify change to a number of classes.

Behavioral design patterns are those that are used to deal with object collaboration and delegation of responsibilities.Essentially, the Observer design pattern is used to define how communication between components in an application interact with each other or notify one another by sending messages.
In this pattern, the subject maintains a list of the observers and then notifies these observers or the dependents as and when a state change happens. You can add or remove observers at runtime as well.To read this article in full or to leave a comment, please click here

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