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Mastering Delphi Programming: A Complete Reference Guide

You're reading from   Mastering Delphi Programming: A Complete Reference Guide Learn all about building fast, scalable, and high performing applications with Delphi

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Product type Course
Published in Nov 2019
Publisher Packt
ISBN-13 9781838989118
Length 674 pages
Edition 1st Edition
Languages
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Author (1):
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Primož Gabrijelčič Primož Gabrijelčič
Author Profile Icon Primož Gabrijelčič
Primož Gabrijelčič
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Toc

Table of Contents (19) Chapters Close

Preface 1. About Performance FREE CHAPTER 2. Fixing the Algorithm 3. Fine-Tuning the Code 4. Memory Management 5. Getting Started with the Parallel World 6. Working with Parallel Tools 7. Exploring Parallel Practices 8. Using External Libraries 9. Introduction to Patterns 10. Singleton, Dependency Injection, Lazy Initialization, and Object Pool 11. Factory Method, Abstract Factory, Prototype, and Builder 12. Composite, Flyweight, Marker Interface, and Bridge 13. Adapter, Proxy, Decorator, and Facade 14. Nullable Value, Template Method, Command, and State 15. Iterator, Visitor, Observer, and Memento 16. Locking Patterns 17. Thread pool, Messaging, Future and Pipeline 18. Other Books You May Enjoy

Singleton

The singleton pattern was part of the original Design Patterns collection. It makes sure that a class, which we call a singleton class, has only one instance. In other words, only one object of that class may ever be created during the program's life. Such a class must also provide global access to this instance.

Let me give a real-life example to clarify this definition. You probably live in a country that allows one, and only one, president (or monarch, head of state, and so on.) to exist at the same time. So, that person is a singleton.

You will notice that the pattern tells us nothing about how that one singleton instance should be destroyed. It also doesn't specify when the singleton instance should be created.

Whenever you need to create a singleton, you should first answer the following questions:

  • Does the singleton have to be initialized on demand...
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