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


All interactive programs are organized around actions. The user presses a key, moves or clicks a mouse, touches the screen, and so on, and the program reacts to that by performing an action. This action frequently has parameters attached to it. For example, a keypress action knows which key was pressed, the screen touch knows the coordinates of a person's touch, and so on. At some time at the very moment the action was triggered the action will result in some operation being executed on some object.

The command pattern helps with organizing such a system by converting actions into objects. Instead of treating the action as a bunch of loosely connected data, the code creates a special object (a command) and stores the action parameters inside this command object. A typical system will know about multiple command types, all of which are realized by subclassing the command object. For example, a keypress would create TKeypressCommand, a mouse move would create the TMouseMove command...