Jawaharlal Nehru Technological University Hyderabad B.Tech IV DESIGN PATTERNS Previous Question Paper (July/August - 2023 - R15)

A design pattern is a reusable, generalized solution to a commonly occurring problem within a given context in software design. It represents a proven template or description of how to solve a problem that can be used in many different situations, rather than a finished piece of code that can be transformed directly into an application.

In the Model-View-Controller (MVC) pattern, the model and view are decoupled primarily through the Observer pattern. The model maintains a list of dependent views and notifies them of any state changes without requiring the model to have explicit knowledge of the view's internal implementation or structure.

This decoupling is achieved through the following mechanisms:

• Notification Mechanism: When the model's data changes, it triggers an update event. The view, acting as an observer, listens for these events and refreshes its display accordingly.
• Lack of Direct Reference: The model does not contain references to view classes or methods, ensuring that the model remains independent of the user interface.
• Interface Abstraction: By using interfaces or event-driven communication, the model interacts with an abstraction of the view, allowing multiple views to be attached or detached at runtime without modifying the model's code.