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

Null object

In object-oriented programming, code sometimes refers to an optional object. The absence of an object doesn't represent an error; it is just an obstacle to writing clean code. Sometimes, we can replace such a missing object (a nil value) with a null object. A null object implements the same interface as a real object, but replaces each method with a do nothing implementation.



Most modern operating systems know about the concept of a null device. For example, NUL on Windows and /dev/null on Unix and similar systems are devices that are empty if we read from them. They will also happily store any file you copy onto them, no matter what the size. You'll never be able to retrieve that file, though, as the null device will stay empty no matter what you do with it.

The null object pattern is a relatively recent addition to the object-oriented programmer's arsenal. It was first introduced in 1996 in a paper by Bobby Woolf, which is still available on the internet at http://www.cs...