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Polished Ruby Programming

You're reading from   Polished Ruby Programming Build better software with more intuitive, maintainable, scalable, and high-performance Ruby code

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Product type Paperback
Published in Jul 2021
Publisher Packt
ISBN-13 9781801072724
Length 434 pages
Edition 1st Edition
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Author (1):
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Jeremy Evans Jeremy Evans
Author Profile Icon Jeremy Evans
Jeremy Evans
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Toc

Table of Contents (23) Chapters Close

Preface 1. Section 1: Fundamental Ruby Programming Principles
2. Chapter 1: Getting the Most out of Core Classes FREE CHAPTER 3. Chapter 2: Designing Useful Custom Classes 4. Chapter 3: Proper Variable Usage 5. Chapter 4: Methods and Their Arguments 6. Chapter 5: Handling Errors 7. Chapter 6: Formatting Code for Easy Reading 8. Section 2: Ruby Library Programming Principles
9. Chapter 7: Designing Your Library 10. Chapter 8: Designing for Extensibility 11. Chapter 9: Metaprogramming and When to Use It 12. Chapter 10: Designing Useful Domain-Specific Languages 13. Chapter 11: Testing to Ensure Your Code Works 14. Chapter 12: Handling Change 15. Chapter 13: Using Common Design Patterns 16. Chapter 14: Optimizing Your Library 17. Section 3: Ruby Web Programming Principles
18. Chapter 15: The Database Is Key 19. Chapter 16: Web Application Design Principles 20. Chapter 17: Robust Web Application Security 21. Assessments 22. Other Books You May Enjoy

Handling cases where there can be only one

In cases where an application using your library should only have a single instance of the object, you usually would reach for the singleton design pattern. Ruby actually has a standard library for the singleton pattern, appropriately named singleton. This library defines the Singleton module, which you can include in other classes to turn those classes into singletons. A class that includes Singleton no longer has a public new method, since you should not be creating multiple instances. Instead, it provides a class method named instance, which returns the only instance of the class:

require 'singleton'
class OnlyOne
  include Singleton
  def foo
    :foo
  end
end
  
only1 = OnlyOne.instance
only2 = OnlyOne.instance
only1.equal?(only2)
# => true

The singleton library does implement the singleton pattern. So why wasn't it discussed in the previous section,...

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