Why do we need observer?

In control theory, a state observer or state estimator is a system that provides an estimate of the internal state of a given real system , from measurements of the input and output of the real system. It is typically computer-implemented, and provides the basis of many practical applications.

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What is an observer method?

The observer method is a Behavioral design Pattern which allows you to define or create a subscription mechanism to send the notification to the multiple objects about any new event that happens to the object that they are observing . The subject is basically observed by multiple objects.

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