Software Engineering: Strategy Design Patterns

Questions and Answers

Which design principle emphasizes programming to an interface rather than an implementation?

Design Principle 1

Design Principle 3

Fly Behavior Principle

Design Principle 2 (correct)

What does the Strategy pattern provide for algorithms within a system?

It enforces a single algorithm for all cases.

It focuses on inheritance rather than composition.

It makes all algorithms immutable.

It encapsulates and makes algorithms interchangeable. (correct)

What is the main purpose of encapsulating behaviors in an abstract class?

To reduce the number of classes in the system.

To enforce a specific algorithm.

To allow behaviors to be defined at compile time.

To hide implementation details. (correct)

What aspect of an application does Design Principle 1 focus on identifying?

The aspects that change and need to be separated. Signup and view all the answers

In the context of the Duck problem, what is a primary advantage of using interfaces?

They facilitate the implementation of dynamic behaviors. Signup and view all the answers

What does the phrase 'favor composition over inheritance' suggest?

Build complex classes by composing simpler ones. Signup and view all the answers

Which design pattern allows for varying algorithms independently of the clients that use them?

Strategy pattern Signup and view all the answers

Why is the `fly()` method in `RubberDuck` defined to do nothing?

Rubber ducks cannot fly. Signup and view all the answers

What are instance variables used for in the context of integrating Duck behavior?

To reference behaviors at runtime. Signup and view all the answers

What is a major flaw highlighted with the Flyable/Quackable interfaces?

They create rigid code structures. Signup and view all the answers

Study Notes

Overview of Design Patterns: Strategy

The Strategy Pattern is integral in software design, allowing algorithms to be defined, encapsulated, and made interchangeable.
Encourages flexibility in algorithm selection and usage independent of client code.

SimUDuck Application

Initial version involved a simple duck simulation app.
Introduction of a feature for flying ducks, leading to complications.

Implementation Issues

RubberDuck class exhibits peculiar behavior:
- quack() method produces a "squeak."
- display() method showcases its rubber duck appearance.
- fly() method is overridden to do nothing, highlighting the problem of fixed behaviors.

Key Observations

Interfaces like Flyable and Quackable may hinder code reuse, suggesting that as software evolves, flexibility is crucial.
Design Patterns serve to separate varying components from stable ones, contributing to code maintainability.

Design Principles

Design Principle 1: Identify varying application aspects and isolate them from constant components. Applied to the Duck problem for better organization.
Design Principle 2: Emphasizes programming to interfaces rather than specific implementations. For instance, distinguishing fly and quack behaviors.

Duck Behavior Integration

Utilizes an abstract class with instance variables that hold behavior references during runtime.
The performXXX method delegates operations to current behaviors, allowing dynamic behavior assignment.
Subclass constructors are responsible for initializing behaviors.

Composition vs. Inheritance

Design Principle 3: Prioritize composition over inheritance to enhance modularity and reduce coupling in the system.

UML Representation

The Strategy Pattern allows various algorithms to be encapsulated and swapped seamlessly, enhancing the architecture of applications.

Practical Example

IArtistRepository interface showcases the concept of abstraction:
- Methods for retrieving and updating artist data.
The ArtistService class uses dependency injection to receive an instance of IArtistRepository, promoting the Strategy Pattern's adaptability in service components.

Description

Explore the Strategy Design Pattern through the example of a SimUDuck app. This quiz covers the implementation of interfaces for creating various duck types, including Flying Ducks and Rubber Ducks. Test your understanding of design patterns and their impact on code reuse and flexibility.