Book Image

Apex Design Patterns

By : Anshul Verma, Jitendra Zaa
Book Image

Apex Design Patterns

By: Anshul Verma, Jitendra Zaa

Overview of this book

Apex is an on-demand programming language providing a complete set of features for building business applications – including data models and objects to manage data. Apex being a proprietor programming language from Salesforce to be worked with multi tenant environment is a lot different than traditional OOPs languages like Java and C#. It acts as a workflow engine for managing collaboration of the data between users, a user interface model to handle forms and other interactions, and a SOAP API for programmatic access and integration. Apex Design Patterns gives you an insight to several problematic situations that can arise while developing on Force.com platform and the usage of Design patterns to solve them. Packed with real life examples, it gives you a walkthrough from learning design patterns that Apex can offer us, to implementing the appropriate ones in your own application. Furthermore, we learn about the creational patterns that deal with object creation mechanism and structural patterns that helps to identify the relationship between entities. Also, the behavioural and concurrency patterns are put forward explaining the communication between objects and multi-threaded programming paradigm respectively. We later on, deal with the issues regarding structuring of classes, instantiating or how to give a dynamic behaviour at a runtime, with the help of anti-patterns. We learn the basic OOPs principal in polymorphic and modular way to enhance its capability. Also, best practices of writing Apex code are explained to differentiate between the implementation of appropriate patterns. This book will also explain some unique patterns that could be applied to get around governor limits. By the end of this book, you will be a maestro in developing your applications on Force.com for Salesforce
Table of Contents (12 chapters)
Apex Design Patterns
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface

The active object pattern


To overcome the preceding race condition in concurrency, we can use the active object pattern.

Note

The active object pattern decouples the method execution from its invocation. Mostly, the active object pattern executes in asynchronous mode. Requesters submit a task as an object in a queue, and a scheduler picks an object from the queue and executes its logic. An object in the queue knows what to do when invoked, and that's the reason why the name of the pattern is active object.

As Apex does not support multithreading, we cannot create a shareable queue, which can be accessed by multiple threads simultaneously; and therefore, we will do it with the help of the  Pending_Request__c custom object. This custom object will save all the necessary information of the pending tasks that need to be performed asynchronously by the active object pattern.

Note

Do not confuse a shareable queue with the Salesforce queue. Here, a queue means a list of objects available in memory...