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Observer and Observer-pattern seem to be synonymous, based on their tag wikis. Is there a difference between the two, if any? Does one refer to the pattern and the other refer to libraries called "observer"?

I'm not much of a design pattern person - I just happened to come across a question asking about observers, and wanted to tag it correctly.

The observer pattern (a subset of the publish/subscribe pattern) is a software design pattern in which an object, called the subject, maintains a list of its dependents, called observers, and notifies them automatically of any state changes, usually by calling one of their methods. It is mainly used to implement distributed event handling systems.

The observer pattern is a software-design pattern where an object (called a subject) maintains a list of its dependents (called observers). Observers subscribe to the subject if they want to be notified of any state changes. In the event of any state changes, the subject notifies the observer, usually by calling one of its methods. This paradigm is commonly used in event-handling systems.

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I would imagine, that would be used for questions involving design of software that uses the pattern, and might be preferential for questions involving the implementation of the actual code.

I haven't studied those tags, so a glance through some of the questions might give you a better idea.

I'm sure, like anything else, there's some ambiguity there, and if it's a hair splitting situation, someone with a deeper expertise can retag if necessary. Maybe leave a comment in that vein if you think it's a concern.

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