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 last pattern in this chapter, state, allows an object to change its behavior on demand. This is especially useful when an object implements an algorithm that goes through different execution states. If the object's internal behavior changes when its state is changed, you've got an excellent candidate for a state pattern.


Any vending machine follows the state pattern. The behavior of a machine when the customer presses the buttons to select a certain product depends on the current state. If the customer has already paid for the product, the machine will deliver the merchandise. Otherwise, it will only display the cost of the product.

This Gang of Four pattern can only be used in rare occasions. A typical candidate for the introduction of this pattern is an object that implements some kind of state machine. Standard examples include TCP socket management, line encryption, text file parsers, and the implementation of painting tools.


For more information about state machines,...