factory Method

Question 1

What is the Factory Method Pattern?

Answer 1

The Factory Method Pattern is a creational design pattern that provides an interface for creating objects while allowing subclasses to decide which specific class to instantiate.

Question 2

What is the main intent of the Factory Method Pattern?

Answer 2

Define an interface for creating an object.

Let subclasses decide which class to instantiate.

Defer instantiation to subclasses.

Question 3

How does the Factory Method Pattern improve flexibility?

Answer 3

It allows new object types to be introduced without modifying the base class.
It decouples client code from the specific concrete classes being instantiated.

Question 4

How does the Factory Method Pattern work?

Answer 4

A base class defines a factory method (createDocument()).

Subclasses override the factory method to specify which type of object to create.

The base class defers instantiation to its subclasses.

Question 5

What real-world analogy can explain the Factory Method Pattern?

Answer 5

A restaurant menu acts as an interface for ordering food.

Each restaurant (subclass) prepares dishes differently, even if they have the same name.

Customers order from the menu but don’t need to know how the dishes are made.

Question 6

What are the components of the Factory Method Pattern?

Answer 6

Abstract Product (e.g., Document) - Defines a common interface.

Concrete Products (e.g., WordDocument, PDFDocument, HTMLDocument) - Implement specific behaviors.

Creator (Base Class) (e.g., Application) - Defines the factory method.

Concrete Creators (Subclasses) (e.g., WordApplication, PDFApplication) - Override the factory method to create specific products.

Question 7

What is an abstract product in the Factory Method Pattern?

Answer 7

It is the base class or interface that defines the common behavior for all objects created by the Factory Method.
Example: Document class in a word processing application.

Question 8

What are concrete products in the Factory Method Pattern?

Answer 8

They are specific implementations of the abstract product.
Example: WordDocument, PDFDocument, HTMLDocument.

Question 9

How does the Factory Method Pattern achieve decoupling?

Answer 9

The base class defines the factory method but doesn’t know which specific subclass will be instantiated.

The subclasses decide which object to create, reducing dependency on specific concrete classes.

Question 10

What are the key benefits of the Factory Method Pattern?

Answer 10

Decouples object creation from client code.
Easier to add new object types without modifying existing code.
Supports flexibility and extensibility.
Encapsulates the object creation process.

Question 11

What are the key takeaways of the Factory Method Pattern?

Answer 11

defines an interface for object creation.

Delegates instantiation to subclasses.

Promotes flexibility and extensibility.

Used when object creation needs to be decoupled from the main program logic.

Question 12

What problem does the Factory Method Pattern solve in software design?

Answer 12

It delegates object creation to subclasses, avoiding hardcoded dependencies.

Question 13

How does the Factory Method Pattern promote flexibility in object creation?

Answer 13

It allows new object types to be introduced without modifying existing code.

Question 14

Why is the Factory Method Pattern classified as a creational design pattern?

Answer 14

Because it focuses on creating objects in a structured and flexible way.

Question 15

How does the Factory Method Pattern help achieve loose coupling between classes?

Answer 15

It separates object creation logic from the client code, reducing dependencies.

Question 16

What is the difference between the Factory Method Pattern and a simple factory?

Answer 16

The Factory Method allows subclasses to decide what to create, while a Simple Factory centralizes object creation.

Question 17

Why does the Factory Method Pattern use inheritance to create objects instead of directly instantiating them in the base class?

Answer 17

To allow subclasses to define specific object creation without modifying the base class.

Question 18

What would happen if an application did not use the Factory Method Pattern but instead directly instantiated objects in the base class?

Answer 18

The base class would be tightly coupled to specific object types, making it harder to extend.

Question 19

How does the Factory Method Pattern help in maintaining the Open-Closed Principle?

Answer 19

New classes can be added without modifying existing code, keeping the system extendable.

Question 20

What is the downside of not using the Factory Method Pattern when working with multiple object types?

Answer 20

The code would require modifications whenever a new type is introduced, violating extensibility.

Question 21

Can the Factory Method Pattern be used with dependency injection? If so, how?

Answer 21

Yes, by injecting the factory into a class instead of hardcoding object creation.

Question 22

What are the key components of the Factory Method Pattern?

Answer 22

Creator (Base Class), Concrete Creator (Subclass), Abstract Product, Concrete Product, and Factory Method.

Question 23

What role does the creator class play in the Factory Method Pattern?

Answer 23

It defines the factory method but does not specify which product to create.

Question 24

What role does the concrete creator play in the Factory Method Pattern?

Answer 24

It overrides the factory method to specify the exact product type to create.

Question 25

What is an abstract product in the Factory Method Pattern?

Answer 25

A common interface for all product types.

Question 26

How do concrete products differ from the abstract product in the Factory Method Pattern?

Answer 26

Concrete products implement the abstract product’s interface with specific behavior.

Question 27

How does polymorphism play a role in the Factory Method Pattern?

Answer 27

The client interacts with abstract products, while the actual object type is decided at runtime.

Question 28

Why does the Factory Method Pattern typically involve an interface or an abstract class?

Answer 28

To allow multiple concrete implementations while ensuring a consistent interface.

Question 29

How does the Factory Method defer object instantiation to its subclasses?

Answer 29

By defining a factory method that subclasses override to create specific objects.

Question 30

What is the difference between a Factory Method and an Abstract Factory?

Answer 30

Factory Method creates a single product type, Abstract Factory creates families of related products.

Question 31

What happens if a subclass forgets to override the Factory Method?

Answer 31

It may result in runtime errors or return a default or null object.

Question 32

How would you apply the Factory Method Pattern to a notification system that sends emails, SMS, and push notifications?

Answer 32

Create a NotificationFactory with subclasses for EmailNotification, SMSNotification, and PushNotification.

Question 33

How would the Factory Method Pattern help in designing a game with different enemy types (e.g., zombies, aliens, robots)?

Answer 33

Each EnemyFactory subclass would create a specific enemy type.

Question 34

How would the Factory Method Pattern be beneficial in a document editor that supports Word, PDF, and HTML file types?

Answer 34

A DocumentFactory can create different document types without modifying the main editor.

Question 35

How would you modify an existing class hierarchy to incorporate the Factory Method Pattern without breaking existing functionality?

Answer 35

Introduce an abstract factory method and move object creation logic to subclasses.

Question 36

What are some disadvantages of using the Factory Method Pattern?

Answer 36

Increased complexity due to extra classes. Overhead from inheritance and subclassing.

Question 37

Give an example where the Factory Method Pattern would not be an ideal choice.

Answer 37

When only one type of object is needed, making a factory unnecessary.

Question 38

How does the Factory Method Pattern compare to using an if-else or switch statement for object creation?

Answer 38

The Factory Method avoids conditional logic, making the code easier to extend.

Question 39

If a software application needs to create different types of database connections (e.g., MySQL, PostgreSQL, SQLite), how can the Factory Method Pattern be used?

Answer 39

A DatabaseConnectionFactory can create different database connection objects based on configuration.

Question 40

Can the Factory Method Pattern be used in multi-threaded applications? If so, what should be considered?

Answer 40

Yes, but thread safety must be ensured when creating shared objects.

Question 41

How would you modify a Factory Method implementation to allow caching of created objects?

Answer 41

Store created objects in a cache (map or dictionary) and reuse them when needed.

Question 42

In the given C++ code snippet, what is the Factory Method? class Document { public: virtual void open() = 0; }; class WordDocument : public Document { public: void open() override { std::cout << "Opening Word document..." << std::endl; } }; class Application { public: virtual Document* createDocument() = 0; }; class WordApplication : public Application { public: Document* createDocument() override { return new WordDocument(); } };

Answer 42

createDocument() in the Application class.

Question 43

What is the Abstract Product in the C++ code snippet? class Document { public: virtual void open() = 0; }; class WordDocument : public Document { public: void open() override { std::cout << "Opening Word document..." << std::endl; } }; class Application { public: virtual Document* createDocument() = 0; }; class WordApplication : public Application { public: Document* createDocument() override { return new WordDocument(); } };

Answer 43

Document class.

Question 44

What is the Concrete Product in the C++ code snippet?

Answer 44

WordDocument class.

Question 45

What is the Creator in the C++ code snippet?

Answer 45

Application class.

Question 46

What is the Concrete Creator in the C++ code snippet?

Answer 46

WordApplication class.

Question 47

How would you modify the Factory Method implementation to support an ExcelDocument?

Answer 47

Create a ExcelDocument class and a ExcelApplication subclass that overrides createDocument().

Question 48

What would happen if a factory method returned a different type of object than expected?

Answer 48

It could break polymorphism and cause runtime errors.

Question 49

What is the benefit of using dynamic binding in the Factory Method Pattern?

Answer 49

It allows runtime selection of the appropriate object type.

Question 50

How can you implement the Factory Method Pattern in Python, Java, or JavaScript?

Answer 50

Python: Use @abstractmethod in a base class. Java: Use an abstract class with abstract createProduct(). JavaScript: Use a factory function or ES6 class with an overridable method.

Question 51

How does the Factory Method Pattern relate to the Abstract Factory Pattern?

Answer 51

Abstract Factory is often implemented using Factory Methods. Each factory method in the Abstract Factory creates a specific product in the product family.

Question 52

How does the Factory Method Pattern relate to the Template Method Pattern?

Answer 52

Factory Methods are often called within Template Methods. Example: The NewDocument() method in an application calls the Factory Method (CreateDocument()) as part of its workflow.

Question 53

How does the Factory Method Pattern differ from the Prototype Pattern?

Answer 53

Factory Method requires subclassing to define which object to create. Prototype does not require subclassing and creates new objects by cloning an existing instance.