Scala Design Patterns

Ivan Nikolov

• Verlag: Packt Publishing
• Jahr: 2016
• ISBN:
  9781785882500
• Auflage: 1
• Thema: Informatique
• Thema: Programmation orientée objet

Write efficient, clean, and reusable code with Scala

About This Book

• Unleash the power of Scala and apply it in the real world
• Increase your efficiency by leveraging the power of Creational, Structural, Behavioural, and Functional design patterns
• Build object oriented and functional applications quickly and effectively

Who This Book Is For

If you want to increase your understanding of Scala and apply it to real-life application development, then this book is for you. We've also designed the book to be used as a quick reference guide while creating applications. Previous Scala programming knowledge is expected.

What You Will Learn

• Immerse yourself in industry-standard design patterns—structural, creational, and behavioral—to create extraordinary applications
• Feel the power of traits and their application in Scala
• Implement abstract and self types and build clean design patterns
• Build complex entity relationships using structural design patterns
• Create applications faster by applying functional design patterns

In Detail

Scala has become increasingly popular in many different IT sectors. The language is exceptionally feature-rich which helps developers write less code and get faster results. Design patterns make developer's lives easier by helping them write great software that is easy to maintain, runs efficiently and is valuable to the company or people concerned.

You will learn about the various features of Scala and be able to apply well-known, industry-proven design patterns in your work. The book starts off by focusing on some of the most interesting features of Scala while using practical real-world examples. We will also cover the popular "Gang of Four" design patterns and show you how to incorporate functional patterns effectively. By the end of this book, you will have enough knowledge and understanding to quickly assess problems and come up with elegant solutions.

Style and approach

The design patterns in the book will be explained using real-world, step-by-step examples. For each design pattern, there will be hints about when to use it and when to look for something more suitable. This book can also be used as a practical guide, showing you how to leverage design patterns effectively.

Scala Design Patterns

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Table of Contents

Scala Design Patterns

Credits

About the Author

Acknowledgments

About the Reviewer

www.PacktPub.com

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Why subscribe?

Free access for Packt account holders

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Downloading the example code

Errata

Piracy

Questions

1. The Design Patterns Out There and Setting Up Your Environment

Design patterns

Scala and design patterns

The need for design patterns and their benefits

Design pattern categories

Creational design patterns

The abstract factory design pattern

The factory method design pattern

The lazy initialization design pattern

The singleton design pattern

The object pool design pattern

The builder design pattern

The prototype design pattern

Structural design patterns

The adapter design pattern

The decorator design pattern

The bridge design pattern

The composite design pattern

The facade design pattern

The flyweight design pattern

The proxy design pattern

Behavioral design patterns

The value object design pattern

The null object design pattern

The strategy design pattern

The command design pattern

The chain of responsibility design pattern

The interpreter design pattern

The iterator design pattern

The mediator design pattern

The memento design pattern

The observer design pattern

The state design pattern

The template method design pattern

The visitor design pattern

Functional design patterns

Monoids

Monads

Functors

Scala-specific design patterns

The lens design pattern

The cake design pattern

Pimp my library

Stackable traits

The type class design pattern

Lazy evaluation

Partial functions

Implicit injection

Duck typing

Memoization

How to choose a design pattern

Setting up the development environment

Installing Scala

Scala IDEs

Dependency management

SBT

Maven

SBT versus Maven

Summary

2. Traits and Mixin Compositions

Traits

Traits as interfaces

Mixing in traits with variables

Traits as classes

Extending classes

Extending traits

Mixin compositions

Mixing traits in

Composing

Composing simple traits

Composing complex traits

Composing with self types

Clashing traits

Same signatures and return types traits

Same signatures and different return types traits

Same signatures and return types mixins

Same signatures and different return types mixins

Multiple inheritance

The diamond problem

The limitations

Linearization

Rules of inheritance hierarchies

Linearization rules

How linearization works

Initialization

Method overriding

Testing traits

Using a class

Mixing the trait in

Mixing into the test class

Mixing into the test cases

Running the tests

Traits versus classes

Summary

3. Unification

Functions and classes

Functions as classes

Function literals

Functions without syntactic sugar

Increased expressivity

Algebraic data types and class hierarchies

ADTs

Sum ADTs

Product ADTs

Hybrid ADTs

The unification

Pattern matching

Pattern matching with values

Pattern matching for product ADTs

Modules and objects

Using modules

Summary

4. Abstract and Self Types

Abstract types

Generics

Abstract types

Generics versus abstract types

Usage advice

Polymorphism

Subtype polymorphism

Parametric polymorphism

Ad hoc polymorphism

Adding functions for multiple types

Self types

Using self types

Requiring multiple components

Conflicting components

Self types and the cake design pattern

Self types versus inheritance

Inheritance leaks functionality

Summary

5. Aspect-Oriented Programming and Components

Aspect-oriented programming

Chapter case example

Without AOP

With AOP

Components in Scala

Scala is rich

Implementing components

Self types for components

Summary

6. Creational Design Patterns

What are creational design patterns?

The factory method design pattern

Class diagram

Code example

Scala alternatives

What is it good for?

What is it not so good for?

The abstract factory

Class diagram

Code example

Scala alternatives

What is it good for?

What is it not so good for?

Other factory design patterns

The static factory

The simple factory

Factory combinations

Lazy initialization

Class diagram

Code example

What is it good for?

What is it not so good for?

The singleton design pattern

Class diagram

Code example

What is it good for?

What is it not so good for?

The builder design pattern

Class diagram

Code example

Java-like implementation

Implementation with a case class

Using generalized type constraints

Changing the Person class

Changing the PersonBuilder class

Adding generalized type constraints to the required methods

Using the type-safe builder

Using require statements

What is it good for?

What is it not so good for?

The prototype design pattern

Class diagram

Code example

What is it good for?

What is it not so good for?

Summary

7. Structural Design Patterns

What are structural design patterns?

The adapter design pattern

Class diagram

Code example

The adapter design pattern with final classes

The adapter design pattern the Scala way

What is it good for?

What is it not so good for?

The decorator design pattern

Class diagram

Code example

The decorator design pattern the Scala way

What is it good for?

What is it not so good for?

The bridge design pattern

Class diagram

Code example

The bridge design pattern the Scala way

What is it good for?

What is it not so good for?

The composite design pattern

Class diagram

Code example

What is it good for?

What is it not so good for?

The facade design pattern

Class diagram

Code example

What is it good for?

What is it not so good for?

The flyweight design pattern

Class diagram

Code example

What is it good for?

What is it not so good for?

The proxy design pattern

Class diagram

Code example

What is it good for?

What is it not so good for?

Summary

8. Behavioral Design Patterns – Part 1

What are behavioral design patterns?

The value object design pattern

Class diagram

Code example

What is it good for?

What is it not so good for?

The null object design pattern

Class diagram

Code example

What is it good for?

What is it not so good for?

The strategy design pattern

Class diagram

Code example

The strategy design pattern the Scala way

The command design pattern

Class diagram

Code example

The command design pattern the Scala way

What is it good for?

What is it not so good for?

The chain of responsibility design pattern

Class diagram

Code example

The chain of responsibility design pattern the Scala way

What is it good for?

What is it not so good for?

The interpreter design pattern

Class diagram

Code example

What is it good for?

What is it not so good for?

Summary

9. Behavioral Design Patterns – Part 2

The iterator design pattern

Class diagram

Code example

What is it good for?

What is it not so good for?

The mediator design pattern

Class diagram

Code example

What is it good for?

What is it not so good for?

The memento design pattern

Class diagram

Code example

What is it good for?

What is it not so good for?

...