Search icon CANCEL
Subscription
0
Cart icon
Your Cart (0 item)
Close icon
You have no products in your basket yet
Arrow left icon
Explore Products
Best Sellers
New Releases
Books
Videos
Audiobooks
Learning Hub
Free Learning
Arrow right icon
Scala Design Patterns
Scala Design Patterns

Scala Design Patterns: Design modular, clean, and scalable applications by applying proven design patterns in Scala , Second Edition

eBook
$27.98 $39.99
Paperback
$48.99
Subscription
Free Trial
Renews at $19.99p/m

What do you get with Print?

Product feature icon Instant access to your digital eBook copy whilst your Print order is Shipped
Product feature icon Paperback book shipped to your preferred address
Product feature icon Download this book in EPUB and PDF formats
Product feature icon Access this title in our online reader with advanced features
Product feature icon DRM FREE - Read whenever, wherever and however you want
OR
Modal Close icon
Payment Processing...
tick Completed

Shipping Address

Billing Address

Shipping Methods
Table of content icon View table of contents Preview book icon Preview Book

Scala Design Patterns

Traits and Mixin Compositions

Before digging into some actual design patterns, we have to make sure that many of the Scala language concepts are clear to the reader. Many of those concepts will later be used in implementing the actual design patterns, and being aware of the possibilities, limitations, and pitfalls are key factors that enable us to correctly and efficiently write code. Even though those concepts are not considered official design patterns, they could still be used to write good software. In some cases, due to the richness of Scala, some concepts could replace a design pattern by just using language features. After all, as we have already said before, design patterns are there because a programming language lacks features and is not rich enough to complete certain tasks.

The first topic that we will look into is about traits and mixin compositions. They provide...

Traits

Many of you might have different perspectives of traits in Scala. They can be viewed not only as interfaces in other languages, but also as classes with only parameter-less constructors.

Trait parameters

The Scala programming language is quite dynamic and has evolved quickly throughout the years. According to the language creators, the Dotty project is the future of Scala and it is a place where passing parameters to traits and many other features are being tested and implemented. The main idea behind it is language simplification, and more information can be found at http://dotty.epfl.ch and https://scala-lang.org/blog/2017/05/31/first-dotty-milestone-release.html.

In the following few sections, we will see the traits from different points of view and try to give you some ideas about how they can be used.

...

Mixin compositions

Scala allows developers to extend many traits in a single class. This adds the possibility of achieving multiple inheritance and saves a lot of effort in code writing, which has to be performed in languages where extending many classes is not allowed. In this subtopic, we will show how traits can be mixed in a specific class or used to create anonymous classes with some specific functionality while writing our code.

Mixing traits in

First of all, let's modify the code from the previous example. It is a really simple change and it will also show exactly how traits can be mixed in:

object MixinRunner extends Ping with Pong {
def main(args: Array[String]): Unit = {
ping()
pong()
}
}

As can be seen...

Multiple inheritance

We inevitably had to mention multiple inheritance in the previous sections due to the fact that we can mix multiple traits and they can all have their own implementations of the methods. Multiple inheritance is not only a powerful technique, but also a dangerous one, and some languages such as Java have decided to not even allow it. As we already saw, Scala allows this, but with some limitations. In this subsection, we will present the problems of multiple inheritance and show how Scala deals with them.

The diamond problem

Multiple inheritance suffers from the diamond problem.

Let's have a look at the following diagram:

Here, both B and C extend A, and then D extends B and C. Some ambiguities might...

Linearization

As we already saw, traits offer a form of multiple inheritance. In such cases, the hierarchy is not necessarily linear, but forms an acyclic graph that needs to be flattened upon compilation. What linearization does is this—it specifies a single linear order for all of the ancestors of a class, including both the regular superclass chain and the parent chains of all of the traits.

We will not have to deal with linearization in traits that contain no code. However, if we use mixins, we will have to consider it. The following will be affected by linearization:

  • Method definitions
  • Variables (both mutable—var and immutable—val)

We already saw a simple example of linearization previously. Things, however, can get much more complicated and unexpected if the rules of linearization are not clear.

...

Testing traits

Testing is a really important part of software development. It ensures that changes to a certain piece of code do not end up producing errors either in the methods that were changed, or somewhere else.

There are different testing frameworks that one can use, and it really is a matter of personal preference. In this book, we have used ScalaTest (http://www.scalatest.org), as this is the one I use in my projects; it is understandable, readable, and easy to use.

In some cases, if a trait is mixed into a class, we could end up testing the class. However, we might want to test only a specific trait. It does not make much sense to test a trait that doesn't have all its methods implemented, so here we will look into the ones that have their code written (mixins). Also, the unit tests that we will show here are quite simple, but they are just for illustration purposes...

Traits versus classes

Traits could be similar, but also very different to classes. It could be hard for a developer to choose which one to use in various cases, but here we will try to provide some general guidelines that should help.

Use classes:

  • When a behavior is not going to be reused at all or in multiple places
  • When you plan to use your Scala code from another language, for example, if you are building a library that could be used in Java

Use traits:

  • When a behavior is going to be reused in multiple unrelated classes.
  • When you want to define interfaces and want to use them outside Scala, for example, Java. The reason is that the traits that do not have any implementations are compiled similar to interfaces.

Summary

In this chapter, we went through traits and mixin compositions in Scala. By now, you should have a good understanding of what these are and what can be achieved by using them. We also went through the examples of the different uses of traits and what to watch out for when using them. We presented the limitations of using traits for multiple inheritance. Traits are an extremely powerful concept, but they have their pitfalls as we saw with multiple inheritance, so you should use them carefully. Linearization was covered in depth and you should be familiar with what to expect when using traits for multiple inheritance and why things work exactly the way they currently do.

Testing is an essential part of every good software project, and we also presented how it should be done for traits. Last, but not least, we prepared a few guidelines that should help developers choose between...

Left arrow icon Right arrow icon

Key benefits

  • •Unleash the power of Scala and apply it in the real world to build scalable and robust applications.
  • •Learn about using and implementing Creational, Structural, Behavioral, and Functional design patterns in Scala
  • •Learn how to build scalable and extendable applications efficiently

Description

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.

Who is this book for?

If you want to increase your understanding of Scala and apply design patterns to real-life application development, then this book is for you.Prior knowledge of Scala language is assumed/ expected.

What you will learn

  • Immerse yourself in industry-standard design patterns—structural, creational, and behavioral—to create extraordinary applications
  • See 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
Estimated delivery fee Deliver to Colombia

Standard delivery 10 - 13 business days

$19.95

Premium delivery 3 - 6 business days

$40.95
(Includes tracking information)

Product Details

Country selected
Publication date, Length, Edition, Language, ISBN-13
Publication date : Apr 09, 2018
Length: 396 pages
Edition : 2nd
Language : English
ISBN-13 : 9781788471305
Category :
Languages :

What do you get with Print?

Product feature icon Instant access to your digital eBook copy whilst your Print order is Shipped
Product feature icon Paperback book shipped to your preferred address
Product feature icon Download this book in EPUB and PDF formats
Product feature icon Access this title in our online reader with advanced features
Product feature icon DRM FREE - Read whenever, wherever and however you want
OR
Modal Close icon
Payment Processing...
tick Completed

Shipping Address

Billing Address

Shipping Methods
Estimated delivery fee Deliver to Colombia

Standard delivery 10 - 13 business days

$19.95

Premium delivery 3 - 6 business days

$40.95
(Includes tracking information)

Product Details

Publication date : Apr 09, 2018
Length: 396 pages
Edition : 2nd
Language : English
ISBN-13 : 9781788471305
Category :
Languages :

Packt Subscriptions

See our plans and pricing
Modal Close icon
$19.99 billed monthly
Feature tick icon Unlimited access to Packt's library of 7,000+ practical books and videos
Feature tick icon Constantly refreshed with 50+ new titles a month
Feature tick icon Exclusive Early access to books as they're written
Feature tick icon Solve problems while you work with advanced search and reference features
Feature tick icon Offline reading on the mobile app
Feature tick icon Simple pricing, no contract
$199.99 billed annually
Feature tick icon Unlimited access to Packt's library of 7,000+ practical books and videos
Feature tick icon Constantly refreshed with 50+ new titles a month
Feature tick icon Exclusive Early access to books as they're written
Feature tick icon Solve problems while you work with advanced search and reference features
Feature tick icon Offline reading on the mobile app
Feature tick icon Choose a DRM-free eBook or Video every month to keep
Feature tick icon PLUS own as many other DRM-free eBooks or Videos as you like for just $5 each
Feature tick icon Exclusive print discounts
$279.99 billed in 18 months
Feature tick icon Unlimited access to Packt's library of 7,000+ practical books and videos
Feature tick icon Constantly refreshed with 50+ new titles a month
Feature tick icon Exclusive Early access to books as they're written
Feature tick icon Solve problems while you work with advanced search and reference features
Feature tick icon Offline reading on the mobile app
Feature tick icon Choose a DRM-free eBook or Video every month to keep
Feature tick icon PLUS own as many other DRM-free eBooks or Videos as you like for just $5 each
Feature tick icon Exclusive print discounts

Frequently bought together


Stars icon
Total $ 146.97
Scala Design Patterns
$48.99
Scala Reactive Programming
$48.99
Learning Scala Programming
$48.99
Total $ 146.97 Stars icon
Banner background image

Table of Contents

13 Chapters
The Design Patterns Out There and Setting Up Your Environment Chevron down icon Chevron up icon
Traits and Mixin Compositions Chevron down icon Chevron up icon
Unification Chevron down icon Chevron up icon
Abstract and Self Types Chevron down icon Chevron up icon
Aspect-Oriented Programming and Components Chevron down icon Chevron up icon
Creational Design Patterns Chevron down icon Chevron up icon
Structural Design Patterns Chevron down icon Chevron up icon
Behavioral Design Patterns – Part One Chevron down icon Chevron up icon
Behavioral Design Patterns – Part Two Chevron down icon Chevron up icon
Functional Design Patterns – the Deep Theory Chevron down icon Chevron up icon
Applying What We Have Learned Chevron down icon Chevron up icon
Real-Life Applications Chevron down icon Chevron up icon
Other Books You May Enjoy Chevron down icon Chevron up icon

Customer reviews

Top Reviews
Rating distribution
Full star icon Full star icon Full star icon Full star icon Half star icon 4.1
(7 Ratings)
5 star 57.1%
4 star 14.3%
3 star 14.3%
2 star 14.3%
1 star 0%
Filter icon Filter
Top Reviews

Filter reviews by




Akram Ahmad Aug 22, 2018
Full star icon Full star icon Full star icon Full star icon Full star icon 5
- I read the first edition of this book (Scala Design Patterns, by Ivan Nikolov) cover to cover when it first came out, and was blown away by the high quality of the content, impressed by the clear presentation.- Well, in the second edition of the book, all that is still there, plus several improvements. Frankly, this is one of my all-time favorite (technical) books that has gotten even better :)- Scala Design Patterns is simply a pleasure to read, with copious code illustrating the ideas, remarkable both for its quality and quantity, and one in which Ivan has shared some of the highest quality Scala (production level) that I have seen to date. Marvelous coverage of design patterns can be found therein.- I thought I knew a thing or two about Scala, and therefore was pleasantly surprised to learn a bunch of great ideas to elevate my coding skills and design repertoire!
Amazon Verified review Amazon
Amazon Customer Dec 29, 2020
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I am loving it! Very clear code samples and plenty of them. Very easy to read.
Amazon Verified review Amazon
Meysam Nov 16, 2019
Full star icon Full star icon Full star icon Full star icon Full star icon 5
This book puts all your language knowledge into practice. The examples are short and clear. I highly recommend it.
Amazon Verified review Amazon
Larry Nov 19, 2020
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Very good book! Some code was over my head, but that is probably due to my own insufficient knowledge of Scala...I've been studying Scala on and off for a few years as a hobby but never did much of a project yet. After finishing this book, I think I will feel more comfortable with Scala so I can finally do a decent project.I definitely would like to encourage Ivan to write additional Scala books.
Amazon Verified review Amazon
Amazon Customer Aug 21, 2019
Full star icon Full star icon Full star icon Full star icon Empty star icon 4
Overall that is good book.
Amazon Verified review Amazon
Get free access to Packt library with over 7500+ books and video courses for 7 days!
Start Free Trial

FAQs

What is the delivery time and cost of print book? Chevron down icon Chevron up icon

Shipping Details

USA:

'

Economy: Delivery to most addresses in the US within 10-15 business days

Premium: Trackable Delivery to most addresses in the US within 3-8 business days

UK:

Economy: Delivery to most addresses in the U.K. within 7-9 business days.
Shipments are not trackable

Premium: Trackable delivery to most addresses in the U.K. within 3-4 business days!
Add one extra business day for deliveries to Northern Ireland and Scottish Highlands and islands

EU:

Premium: Trackable delivery to most EU destinations within 4-9 business days.

Australia:

Economy: Can deliver to P. O. Boxes and private residences.
Trackable service with delivery to addresses in Australia only.
Delivery time ranges from 7-9 business days for VIC and 8-10 business days for Interstate metro
Delivery time is up to 15 business days for remote areas of WA, NT & QLD.

Premium: Delivery to addresses in Australia only
Trackable delivery to most P. O. Boxes and private residences in Australia within 4-5 days based on the distance to a destination following dispatch.

India:

Premium: Delivery to most Indian addresses within 5-6 business days

Rest of the World:

Premium: Countries in the American continent: Trackable delivery to most countries within 4-7 business days

Asia:

Premium: Delivery to most Asian addresses within 5-9 business days

Disclaimer:
All orders received before 5 PM U.K time would start printing from the next business day. So the estimated delivery times start from the next day as well. Orders received after 5 PM U.K time (in our internal systems) on a business day or anytime on the weekend will begin printing the second to next business day. For example, an order placed at 11 AM today will begin printing tomorrow, whereas an order placed at 9 PM tonight will begin printing the day after tomorrow.


Unfortunately, due to several restrictions, we are unable to ship to the following countries:

  1. Afghanistan
  2. American Samoa
  3. Belarus
  4. Brunei Darussalam
  5. Central African Republic
  6. The Democratic Republic of Congo
  7. Eritrea
  8. Guinea-bissau
  9. Iran
  10. Lebanon
  11. Libiya Arab Jamahriya
  12. Somalia
  13. Sudan
  14. Russian Federation
  15. Syrian Arab Republic
  16. Ukraine
  17. Venezuela
What is custom duty/charge? Chevron down icon Chevron up icon

Customs duty are charges levied on goods when they cross international borders. It is a tax that is imposed on imported goods. These duties are charged by special authorities and bodies created by local governments and are meant to protect local industries, economies, and businesses.

Do I have to pay customs charges for the print book order? Chevron down icon Chevron up icon

The orders shipped to the countries that are listed under EU27 will not bear custom charges. They are paid by Packt as part of the order.

List of EU27 countries: www.gov.uk/eu-eea:

A custom duty or localized taxes may be applicable on the shipment and would be charged by the recipient country outside of the EU27 which should be paid by the customer and these duties are not included in the shipping charges been charged on the order.

How do I know my custom duty charges? Chevron down icon Chevron up icon

The amount of duty payable varies greatly depending on the imported goods, the country of origin and several other factors like the total invoice amount or dimensions like weight, and other such criteria applicable in your country.

For example:

  • If you live in Mexico, and the declared value of your ordered items is over $ 50, for you to receive a package, you will have to pay additional import tax of 19% which will be $ 9.50 to the courier service.
  • Whereas if you live in Turkey, and the declared value of your ordered items is over € 22, for you to receive a package, you will have to pay additional import tax of 18% which will be € 3.96 to the courier service.
How can I cancel my order? Chevron down icon Chevron up icon

Cancellation Policy for Published Printed Books:

You can cancel any order within 1 hour of placing the order. Simply contact [email protected] with your order details or payment transaction id. If your order has already started the shipment process, we will do our best to stop it. However, if it is already on the way to you then when you receive it, you can contact us at [email protected] using the returns and refund process.

Please understand that Packt Publishing cannot provide refunds or cancel any order except for the cases described in our Return Policy (i.e. Packt Publishing agrees to replace your printed book because it arrives damaged or material defect in book), Packt Publishing will not accept returns.

What is your returns and refunds policy? Chevron down icon Chevron up icon

Return Policy:

We want you to be happy with your purchase from Packtpub.com. We will not hassle you with returning print books to us. If the print book you receive from us is incorrect, damaged, doesn't work or is unacceptably late, please contact Customer Relations Team on [email protected] with the order number and issue details as explained below:

  1. If you ordered (eBook, Video or Print Book) incorrectly or accidentally, please contact Customer Relations Team on [email protected] within one hour of placing the order and we will replace/refund you the item cost.
  2. Sadly, if your eBook or Video file is faulty or a fault occurs during the eBook or Video being made available to you, i.e. during download then you should contact Customer Relations Team within 14 days of purchase on [email protected] who will be able to resolve this issue for you.
  3. You will have a choice of replacement or refund of the problem items.(damaged, defective or incorrect)
  4. Once Customer Care Team confirms that you will be refunded, you should receive the refund within 10 to 12 working days.
  5. If you are only requesting a refund of one book from a multiple order, then we will refund you the appropriate single item.
  6. Where the items were shipped under a free shipping offer, there will be no shipping costs to refund.

On the off chance your printed book arrives damaged, with book material defect, contact our Customer Relation Team on [email protected] within 14 days of receipt of the book with appropriate evidence of damage and we will work with you to secure a replacement copy, if necessary. Please note that each printed book you order from us is individually made by Packt's professional book-printing partner which is on a print-on-demand basis.

What tax is charged? Chevron down icon Chevron up icon

Currently, no tax is charged on the purchase of any print book (subject to change based on the laws and regulations). A localized VAT fee is charged only to our European and UK customers on eBooks, Video and subscriptions that they buy. GST is charged to Indian customers for eBooks and video purchases.

What payment methods can I use? Chevron down icon Chevron up icon

You can pay with the following card types:

  1. Visa Debit
  2. Visa Credit
  3. MasterCard
  4. PayPal
What is the delivery time and cost of print books? Chevron down icon Chevron up icon

Shipping Details

USA:

'

Economy: Delivery to most addresses in the US within 10-15 business days

Premium: Trackable Delivery to most addresses in the US within 3-8 business days

UK:

Economy: Delivery to most addresses in the U.K. within 7-9 business days.
Shipments are not trackable

Premium: Trackable delivery to most addresses in the U.K. within 3-4 business days!
Add one extra business day for deliveries to Northern Ireland and Scottish Highlands and islands

EU:

Premium: Trackable delivery to most EU destinations within 4-9 business days.

Australia:

Economy: Can deliver to P. O. Boxes and private residences.
Trackable service with delivery to addresses in Australia only.
Delivery time ranges from 7-9 business days for VIC and 8-10 business days for Interstate metro
Delivery time is up to 15 business days for remote areas of WA, NT & QLD.

Premium: Delivery to addresses in Australia only
Trackable delivery to most P. O. Boxes and private residences in Australia within 4-5 days based on the distance to a destination following dispatch.

India:

Premium: Delivery to most Indian addresses within 5-6 business days

Rest of the World:

Premium: Countries in the American continent: Trackable delivery to most countries within 4-7 business days

Asia:

Premium: Delivery to most Asian addresses within 5-9 business days

Disclaimer:
All orders received before 5 PM U.K time would start printing from the next business day. So the estimated delivery times start from the next day as well. Orders received after 5 PM U.K time (in our internal systems) on a business day or anytime on the weekend will begin printing the second to next business day. For example, an order placed at 11 AM today will begin printing tomorrow, whereas an order placed at 9 PM tonight will begin printing the day after tomorrow.


Unfortunately, due to several restrictions, we are unable to ship to the following countries:

  1. Afghanistan
  2. American Samoa
  3. Belarus
  4. Brunei Darussalam
  5. Central African Republic
  6. The Democratic Republic of Congo
  7. Eritrea
  8. Guinea-bissau
  9. Iran
  10. Lebanon
  11. Libiya Arab Jamahriya
  12. Somalia
  13. Sudan
  14. Russian Federation
  15. Syrian Arab Republic
  16. Ukraine
  17. Venezuela