Book Image

Scala Design Patterns - Second Edition

By : Ivan Nikolov
Book Image

Scala Design Patterns - Second Edition

By: Ivan Nikolov

Overview of this book

Design patterns make developers’ 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’ll learn about the various features of Scala and will 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 and latest features of Scala while using practical real-world examples. We will be learning about IDE’s and Aspect Oriented Programming. We will be looking into different components in Scala. We will also cover the popular "Gang of Four" design patterns and show you how to incorporate functional patterns effectively. The book ends with a practical example that demonstrates how the presented material can be combined in real-life applications. You’ll learn the necessary concepts to build enterprise-grade applications. By the end of this book, you’ll have enough knowledge and understanding to quickly assess problems and come up with elegant solutions.

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Table of Contents (14 chapters)
Preface
Preface
Who this book is for
What this book covers
To get the most out of this book
Get in touch
Free Chapter
1
The Design Patterns Out There and Setting Up Your Environment
The Design Patterns Out There and Setting Up Your Environment
Design patterns
Design pattern categories
Choosing a design pattern
Setting up the development environment
Summary
2
Traits and Mixin Compositions
Traits and Mixin Compositions
Traits
Mixin compositions
Multiple inheritance
Linearization
Testing traits
Traits versus classes
Summary
3
Unification
Unification
Functions and classes
Algebraic data types and class hierarchies
Modules and objects
Summary
4
Abstract and Self Types
Abstract and Self Types
Abstract types
Polymorphism
Self types
Summary
5
Aspect-Oriented Programming and Components
Aspect-Oriented Programming and Components
Aspect-oriented programming
Components in Scala
Summary
6
Creational Design Patterns
Creational Design Patterns
What are creational design patterns?
The factory method design pattern
The abstract factory
Other factory design patterns
Lazy initialization
The singleton design pattern
The builder design pattern
The prototype design pattern
Summary
7
Structural Design Patterns
Structural Design Patterns
Defining 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
Summary
8
Behavioral Design Patterns – Part One
Behavioral Design Patterns – Part One
Defining 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
Summary
9
Behavioral Design Patterns – Part Two
Behavioral Design Patterns – Part Two
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
Summary
10
Functional Design Patterns – the Deep Theory
Functional Design Patterns – the Deep Theory
Abstraction and vocabulary
Monoids
Functors
Monads
Summary
11
Applying What We Have Learned
Applying What We Have Learned
The lens design pattern
The cake design pattern
The pimp my library design pattern
The stackable traits design pattern
The type class design pattern
Lazy evaluation
Partial functions
Implicit injection
Duck typing
Memoization
Summary
12
Real-Life Applications
Real-Life Applications
Reasons to use libraries
The Scalaz library
Writing a complete application
Summary
13
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Functions and classes

In Scala, every value is an object. Functions are first-class values, which also makes them objects of their respective classes.

The following diagram shows the Scala unified type system and how this is achieved. It is adapted from http://www.scala-lang.org/old/sites/default/files/images/classhierarchy.png and represents an up-to-date view of the model (some classes such as ScalaObject have disappeared, as we have already mentioned earlier):

As you can see, Scala does not have the same concept of primitive types that Java has, and all types are ultimately subtypes of Any.

Functions as classes

The fact that functions are classes means that they can be freely passed to other methods or classes as if they...

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