Software Architecture & Design Patterns

Question 1

Why use design patterns?

Answer 1

• Reusability: Pre-tested solutions
• Communication: Shared vocabulary
• Maintainability: Organised code
• Scalability: Adaptable structure

Question 2

How does the Singleton pattern work?

Answer 2

1. Private constructor (prevents direct instantiation)
2. Static instance (ensures single instance)
3. Public getInstance() method (global access)

Question 3

Name three creational patterns and their purposes

Answer 3

• Factory: Creates objects without specifying classes
• Builder: Constructs complex objects step-by-step
• Singleton: Ensures there’s only one instance in a class

Question 4

What are creational patterns?

Answer 4

Patterns focused on object creation

Question 5

What are the 3 MVC components?

Answer 5

1. Model: Manages data
2. View: Displays data
3. Controller: Handles input and updates Model/View

Question 6

What does the Model do in MVC?

Answer 6

Stores data, Enforces business rules, Notifies View of updates

Question 7

What is the View’s role in MVC?

Answer 7

Displays data from Model, No business logic, Updates when Model changes

Question 8

What does the Controller handle?

Answer 8

Processes user input, Updates Model, Refreshes View

Question 9

Describe MVC flow for a bank transfer

Answer 9

1. User (initiateTransfer) -> Controller (validateTransfer)
2. Controller updates Model (updateBalance)
3. Controller refreshes View (displayNewBalance)

Question 10

How does MVC improve maintainability?

Answer 10

Changes to one component (e.g View) don’t affect others (Model/Controller)

Question 11

Name three structural patterns

Answer 11

• Adapter: Allows two incompatible interfaces to collaborate
• Decorator: Adds behaviours to objects dynamically without altering existing code
• Composite: Composes objects into tree-like structures

Question 12

What are structural patterns?

Answer 12

Patterns dealing with object composition/relationships

Question 13

What are behaviour patterns?

Answer 13

Patterns managing object communication.

Question 14

Name three behaviour patterns

Answer 14

• Objects: how a group of objects interact based on state changes
• Strategy: indirectly alters object’s behaviour at runtime
• Command: turns request into a stand-alone object (command)

Question 15

Why is MVC easier to test?

Answer 15

Components are isolated

Question 16

How to make Singleton thread-safe?

Answer 16

Use synchronised in getInstance() or static initialisation

Question 17

Name an MVC variant

Answer 17

MVVM (Model-View-View-Model) for data-binding (e.g. Angular)

Question 18

MVC key rules

Answer 18

• Model: Only data (no logic)
• Controller: Orchestrates logic/updates (all communication flows here)
• View: Passive display

Question 19

When should you use design patterns?

Answer 19

When they solve a specific problem - not as a default. Overuse adds complexity

Question 20

What are design patterns?

Answer 20

Reusable solutions to common software design problems providing structured approaches to improve code readability and flexibility

Question 21

Advantages of MVC

Answer 21

• Modularity (easy updates)
• Scalability (add features without disruption)
• Testability (isolated component testing)
• Flexibility (multiple UIs for same Model)

Question 22

MVC Flow over Traditional flow

Answer 22

Replaces direct interaction with centralised control (Controller), reducing complexity