The observer design pattern is used in applications based on components, whose status:
- is closely monitored by other components on the one hand, and;
- is subject to regular changes on the other.
The typical application cases include GUIs (graphical user interfaces), which provide users with an easy-to-use interface for communicating with software. As soon as data is changed, these changes have to be updated in all GUI components – a scenario ideally covered by the subject/observer structure of the observer pattern. Even programs that work with datasets to be visualised (whether classic tables or graphic diagrams) also benefit from the design pattern structure.
In terms of the programming language used, there are no specific restrictions in principle for the observer design pattern. All that is important is that the object-oriented paradigm is supported, so that an implementation of the pattern also makes sense. Languages in which the use of the pattern is very popular include C#, C++, Java, JavaScript, Python, and PHP.