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


The decorator pattern is an incredibly useful tool that helps you enhance existing interfaces with an additional functionality and without changing the original implementation. In addition to that, we can apply this additional functionality to any subclass of the original implementation. As such, the decorator is a useful tool for enhancing existing behavior.


A Christmas tree by itself doesn't do much. It stands in one place and looks nice. We can, however, enhance its value by adding decorations, such as colorful lights. This decoration doesn't change the original interface of the tree—it just improves it. Furthermore, we can apply the same decoration to many different kinds of trees, not just a specific sort.

Every decorator operates on an existing interface, which is used in two different places. As it has to support original functionality, it must somehow wrap the original interface. Typically, we use an injection to pass the original component to the decorator's constructor...