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 6. Nullable Value, Template Method, Command, and State

Every moderately complex program is a collection of many interlocked parts. In Delphi, as in other object—oriented languages, these parts are represented by objects that can cooperate in different ways. They can be tightly connected one object can own others, or they may just cooperate for a short time.

As with every complex system, there's a big chance that it will evolve into a big mess of parts that are connected in random ways without any order and reason. (Sometimes, we affectionately call such a mess a big ball of mud. It is not a pleasant sight.) The patterns in the behavioral group help us to organize objects so that they are tightly coupled where they have to be, can cooperate with each other when the need occurs, and ignore each other in almost all other instances.

In this chapter, you will learn about the following topics:

  • The null object pattern, which can reduce the need for frequent if statements in the code
  • The Template...