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

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Apex Design Patterns
Anshul Verma | Jitendra Zaa
Apr, 2016 | 256 pages
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Table of Contents (12 chapters)
Apex Design Patterns
Apex Design Patterns
Credits
Credits
About the Authors
About the Authors
About the Reviewer
About the Reviewer
www.PacktPub.com
www.PacktPub.com
Preface
Preface
Free Chapter
1
An Introduction to Apex Design Pattern
An Introduction to Apex Design Pattern
Innovation
Design patterns and learning
Object-Oriented Programming (OOP)
OOPs in play
An interface
An abstract class
Advantages of design patterns
Design patterns and Apex
Gang of Four (GoF)
The SOLID principle
Summary
2
Creational Patterns
Creational Patterns
Factory method pattern
Abstract factory pattern
The singleton pattern
The builder pattern
The prototype pattern
Summary
3
Structural Patterns
Structural Patterns
The facade pattern
The adapter pattern
The bridge pattern
The composite pattern
The decorator pattern
The flyweight pattern
Summary
4
Behavioral Patterns
Behavioral Patterns
The chain of responsibility pattern
The command pattern
The interpreter pattern
The iterator pattern
The visitor pattern
The memento pattern
The observer pattern
The state pattern 
The strategy pattern
Summary
5
Handling Concurrency in Apex
Handling Concurrency in Apex
Understanding concurrency issues
Reproducing concurrency problems in Apex
The active object pattern
Summary
6
Anti-patterns and Best Practices
Anti-patterns and Best Practices
Over usage of formula fields
Functional decomposition
Ignoring the equals() and hashcode() methods while performing object comparison
Circular dependencies
The ignoring toString() method
Avoid the God class
Error hiding
Hard-coding
Magic strings and numbers
Inheritance hell
SOQL inside a loop
DML inside a loop
Summary

DML inside a loop

As in the case of the previous anti-pattern, Salesforce imposes another governor limit known as total number of DML statements issued in a single request. As the name implies, it restricts the number of Data Manipulation Language (DML) statements. For example, insert, update, delete, undelete, and so on.

Note

You can get a comprehensive list of all the DML statements in the official documentation at https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_gov_limits.htm.

Our business requirement is to create a contact for each account inserted. So, we developed our code, as follows:

trigger AccountCreation on Account (after insert) { 
    /* Iterate over all accounts inserted */ 
    for(Account account : Trigger.new){ 
        /* generate new account */ 
        Contact c = new Contact(LastName = account.Name, accountid = account.id); 
        insert c; 
    } 
}

The preceding trigger will fail after processing...

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