Behavioral patterns (Observer, Strategy, Command) in Software Engineering - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the Observer Pattern

Which of the following best describes the main purpose of the Observer pattern?

A To encapsulate a family of algorithms and make them interchangeable.

B To allow an object to notify other objects automatically when its state changes.

C To encapsulate a request as an object, allowing parameterization of clients with queues or logs.

D To create a single instance of a class and provide a global point of access to it.

💡 Hint

Think about how objects communicate changes to others without tight coupling.

The Observer pattern defines a one-to-many dependency so that when one object changes state, all its dependents are notified and updated automatically.

📋 Factual

intermediate

Strategy Pattern Purpose

What is the primary benefit of using the Strategy pattern in software design?

A It provides a way to observe changes in an object's state.

B It ensures only one instance of a class exists throughout the application.

C It allows an object to change its behavior at runtime by switching between different algorithms.

D It queues commands to be executed later or in a different order.

💡 Hint

Consider how you might swap different ways of doing something without changing the client code.

The Strategy pattern enables selecting an algorithm's behavior at runtime by encapsulating each algorithm inside a separate class.

🔍 Analysis

advanced

Command Pattern Use Case Analysis

Which scenario best illustrates the use of the Command pattern?

A Implementing undo and redo functionality by storing commands as objects.

B Changing the sorting algorithm used by a list at runtime.

C Notifying multiple objects when a data model changes.

D Ensuring only one database connection instance is used.

💡 Hint

Think about how actions can be encapsulated and managed independently.

The Command pattern encapsulates a request as an object, allowing for parameterization, queuing, logging, and supporting undoable operations.

❓ Comparison

advanced

Distinguishing Observer and Command Patterns

Which statement correctly distinguishes the Observer pattern from the Command pattern?

A Observer ensures a single instance of a class; Command queues commands for execution.

B Observer encapsulates requests as objects; Command notifies multiple objects about state changes.

C Both patterns are used to change an object's behavior at runtime by switching algorithms.

D Observer focuses on notifying multiple objects about state changes; Command encapsulates requests as objects to be executed later.

💡 Hint

Focus on the main intent and typical use cases of each pattern.

The Observer pattern is about notifying dependents of state changes, while the Command pattern encapsulates requests as objects for flexible execution.

❓ Reasoning

expert

Choosing the Right Behavioral Pattern

You are designing a text editor that needs to support multiple text formatting algorithms, notify UI components when the document changes, and allow undo/redo of user actions. Which combination of behavioral patterns best fits these requirements?

A Strategy for formatting, Observer for UI updates, Command for undo/redo.

B Observer for formatting, Command for UI updates, Strategy for undo/redo.

C Command for formatting, Strategy for UI updates, Observer for undo/redo.

D Strategy for formatting, Command for UI updates, Observer for undo/redo.

💡 Hint

Match each pattern's main purpose to the feature it best supports.

Strategy allows swapping formatting algorithms; Observer notifies UI components of changes; Command encapsulates user actions for undo/redo.