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
Contributors
Preface
Index

Composite


Sometimes, we have to work with data that is organized into a tree structure. There is an entry point, an object of some class N, which owns other objects of the same class N or objects of class L. We call this entry point a root, class N, an inner node, and L, a leaf.

When we perform some operation on such compound data, it is helpful if we can treat all objects the same. In other words, we don't want to distinguish between a root, an inner node, and a leaf. The composite pattern allows us to treat all types of components the same.

Note

Imagine an irrigation system. At some point, it is connected to a water supply. The irrigation system can then split into multiple branches that end in different kinds of water dispensers. We don't care much about that complicated structure, as all components of the system implement the same interface: you put the water in and it flows out the other end.

As specified in the Gang of Four book, a composite pattern works with two types of objects. Compound...