Book Image

Hands-On Design Patterns with Delphi

By : Primož Gabrijelčič
Book Image

Hands-On Design Patterns with Delphi

By: Primož Gabrijelčič

Overview of this book

Design patterns have proven to be the go-to solution for many common programming scenarios. This book focuses on design patterns applied to the Delphi language. The book will provide you with insights into the language and its capabilities of a runtime library. You'll start by exploring a variety of design patterns and understanding them through real-world examples. This will entail a short explanation of the concept of design patterns and the original set of the 'Gang of Four' patterns, which will help you in structuring your designs efficiently. Next, you'll cover the most important 'anti-patterns' (essentially bad software development practices) to aid you in steering clear of problems during programming. You'll then learn about the eight most important patterns for each creational, structural, and behavioral type. After this, you'll be introduced to the concept of 'concurrency' patterns, which are design patterns specifically related to multithreading and parallel computation. These will enable you to develop and improve an interface between items and harmonize shared memories within threads. Toward the concluding chapters, you'll explore design patterns specific to program design and other categories of patterns that do not fall under the 'design' umbrella. By the end of this book, you'll be able to address common design problems encountered while developing applications and feel confident while building scalable projects.
Table of Contents (18 chapters)
Title Page
Copyright and Credits
About Packt

Chapter 2. Singleton, Dependency Injection, Lazy Initialization, and Object Pool

In Object-Oriented Programming (OOP), everything starts with an object, and if we want to use one, we have to create it first. In most cases, that simply means calling TSomeClass.Create, but in a more complex scenario, a specialized design pattern that creates an object for us can be quite handy.

In this chapter, we'll look into four patterns from the creational group. At the end of the chapter, you'll know the following:

  • A singleton pattern, which makes sure that a class has only one instance
  • A dependency injection pattern, which makes program architecture more flexible and suitable for test-driven development
  • A lazy initialization pattern, which makes sure that we don't spend time and resources creating objects that we don't really need
  • An object pool pattern, which speeds up the creation of objects that take a long time to create