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Hands-On Design Patterns and Best Practices with Julia

By Tom Kwong
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  1. Free Chapter
    Design Patterns and Related Principles
About this book
Design patterns are fundamental techniques for developing reusable and maintainable code. They provide a set of proven solutions that allow developers to solve problems in software development quickly. This book will demonstrate how to leverage design patterns with real-world applications. Starting with an overview of design patterns and best practices in application design, you'll learn about some of the most fundamental Julia features such as modules, data types, functions/interfaces, and metaprogramming. You'll then get to grips with the modern Julia design patterns for building large-scale applications with a focus on performance, reusability, robustness, and maintainability. The book also covers anti-patterns and how to avoid common mistakes and pitfalls in development. You'll see how traditional object-oriented patterns can be implemented differently and more effectively in Julia. Finally, you'll explore various use cases and examples, such as how expert Julia developers use design patterns in their open source packages. By the end of this Julia programming book, you'll have learned methods to improve software design, extensibility, and reusability, and be able to use design patterns efficiently to overcome common challenges in software development.
Publication date:
January 2020
Publisher
Packt
Pages
532
ISBN
9781838648817

 

Design Patterns and Related Principles

Nowadays, learning and applying design patterns is an important aspect of software engineering. Design patterns are like water – you can't live without them. Don't believe me? Just ask hiring managers, and you will find that many of them have design patterns in their job postings as well as related questions in job interviews. It is a common belief that design patterns are important ingredients for software development and everyone should know them.

In this chapter, we will provide some context about why design patterns are useful and how they have served us well in the past few decades. By understanding the motivation behind design patterns, we will be able to set forth a set of guiding principles for developing software. The following topics will be discussed in this chapter:

  • The history of design patterns 
  • Software...
 

The history of design patterns

Design patterns is not a new concept to computer programmers. Since personal computers became more affordable and popular in the 1980s, the programming profession flourished and a lot of code was written for a variety of applications.

I remember that, when I was 14 years old, learning the GOTO statement for a BASIC program was one of the coolest things. It literally allowed me to take a control flow to a different part of the code at any time. Perhaps not too surprisingly, when I learned about structured programming and the Pascal language in college, I started to realize how GOTO statements produce messy spaghetti code. Using GOTO for branching purposes is a pattern. It's just a bad one because it makes code difficult to understand, follow, and debug. In today's lingua franca, we call them anti-patterns. When it comes to...

 

Software design principles

While this book does not cover object-oriented programming, some object-oriented design principles are universal and could be applied to any programming language and paradigm. Here, we will take a look at some of the most well-known design principles. In particular, we will cover the following:

  • SOLID: Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, Dependency Inversion
  • DRY: Don't Repeat Yourself
  • KISS: Keep It Simple, Stupid!
  • POLA: Principle of Least Astonishment
  • YAGNI: You Aren't Gonna Need It
  • POLP: Principle of Least Privilege

Let's start with SOLID.

SOLID

The SOLID principle consists of the following:

  • S: Single Responsibility Principle
  • O: Open...
 

Software quality objectives

Everyone likes beautiful design. I do, too. But, the use of design patterns is not just to make something look good. Everything we do should have a purpose.

The GoF classified object-oriented design patterns as creational, structural, and behavioral. For Julia, let's take a different perspective and classify our patterns by their respective software quality objectives as follows:

  • Reusability
  • Performance
  • Maintenance
  • Safety

Let's understand each of these in the following sections.

Reusability

People often talk about top-down and bottom-up approaches when designing software.

The top-down approach starts with a large problem and breaks it down into a set of smaller problems. Then, if the...

 

Summary

In this chapter, we started by going back in time and reviewing the history of design patterns. We discussed why design patterns can be useful for software professionals and how we would like to organize design patterns in this book given what we have learned in the past. 

We went over several key software design principles that can be applied universally in any programming language, as it is important that we keep them in mind when developing code and applying design patterns in Julia. We covered SOLID, DRY, KISS, POLA, YAGNI, and POLP. These design principles are well known and well received by the object-oriented programming community.

Finally, we discussed some software quality objectives that we want to achieve by using design patterns. In this book, we have decided to focus on reusability, maintainability, performance, and safety objectives. We also appreciated...

 

Questions

Review the following questions to reinforce your understanding of the subjects in this chapter. Answers are provided at the back of the book:

  1. What are the benefits of using design patterns?
  2. Name some key design principles.
  3. What problem does the Open/Closed Principle solve?
  4. Why is interface segregation important for software reusability?
  5. What are the simplest ways to keep an application maintainable?
  6. What is a good practice for avoiding over-engineered and bloated software?
  7. How does memory usage affect system performance?
About the Author
  • Tom Kwong

    Tom Kwong, CFA, is an experienced software engineer with over 25 years of industry programming experience. He has spent the majority of his career in the financial services industry. His expertise includes software architecture, design, and the development of trading/risk systems. Since 2017, he has uncovered the Julia language and has worked on several open source packages, including SASLib.jl. He currently works at Western Asset Management Company, a prestige asset management company that specializes in fixed income investment services. He holds an MS degree in computer science from the University of California, Santa Barbara (from 1993), and he holds the Chartered Financial Analyst designation since 2009.

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Latest Reviews (14 reviews total)
It's a fantastic book, full of tips and insights. I have already read it once but plan to do it again.
Seems like a good book, if only I could have it in print.
Very competent and useful book.
Hands-On Design Patterns and Best Practices with Julia
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