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 iterator pattern shows us how to separate the internal structure of a data container from the code that operates on it. A visitor pattern is similar in topic, but applies not so much to composite data as to composite objects. It shows how to implement an algorithm/object separation, which allows us to add new operations to existing objects without modifying their structure. As such, it represents a good example of the Open/Closed principle in practice.

In classical object-oriented code, a part of code (an algorithm) would take an object, inspect its internal structure, and operate on its parts. If we use the visitor pattern, this approach is turned on its head. The algorithm merely passes a method to the object and kindly asks it to execute that method on its constituent parts.


After you enter a city sightseeing bus, you have no longer control over your transportation. The bus driver drives you from one attraction to another and on each stop allows you to perform an action...