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

Proxy


A proxy is a component that wraps another component and exposes the wrapped interface. This definition doesn't make much sense. Why would anyone want to add another layer of indirection (another wrapper) and expose the same wrapped interface? They would do this simply because a proxy doesn't guarantee that each call of that interface will be forwarded to the wrapped object. It is entirely possible that the proxy will generate the result internally or execute something else (introduce a side effect) before or after calling the wrapped interface.

Note

When you are accessing the web from inside a business environment, the traffic usually flows through a http filtering and caching proxy. This software catches all http requests generated in browsers and other applications and then decides whether it will forward a request to the target site, return the result from the cache, or deny the request if the site is on the blocked list.

 

In that example, an http proxy checks whether the access is...