CPP Design Patterns & Architecture 3

Question 1

Which pattern is best suited for implementing undo/redo functionality in an application?

Accepted Answer

Command

Answer

The Command pattern encapsulates operations as objects with execute/undo methods, making undo/redo straightforward.

Question 2

In the Flyweight pattern, what is the key distinction between intrinsic and extrinsic state?

Accepted Answer

Intrinsic state is shared across instances; extrinsic state is context-specific

Answer

Flyweight stores intrinsic (invariant) state internally and receives extrinsic (varying) state from the client at runtime.

Question 3

Which architectural pattern divides an application into Model, View, and Presenter components?

Accepted Answer

MVP

Answer

MVP (Model-View-Presenter) replaces the Controller with a Presenter that mediates between View and Model with no direct View-Model connection.

Question 4

What is the primary intent of the Null Object pattern?

Accepted Answer

Represent missing objects with a no-op implementation to avoid null checks

Answer

Null Object provides a default do-nothing implementation, eliminating the need for null checks scattered throughout client code.

Question 5

In the Visitor pattern, what is 'double dispatch' and why is it needed?

Accepted Answer

Two virtual calls that resolve the concrete types of both the visitor and the element

Answer

Double dispatch uses two polymorphic calls — one on the element to accept a visitor, and one on the visitor to act on the concrete element type.

(CPP) C++ Programming Professional Certificate Practice Test