df15 - dynamic apex binding with design patterns

Dynamic Apex Binding

Eric Leung Salesforce Solution Architect eric.leung@fronde.com @erichpleung

With Design Patterns

Ben Naylor Senior Salesforce Technical Consultant ben.naylor@fronde.com @nzchicken

Australia

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8 YearsSalesforce Partnership

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Key Capabilities Offered by Fronde

Agenda

Part 1: Design Patterns

• Factory and Proxy Patterns

Part 2: Custom Settings and Schema Namespace

Part 3: Dynamic Binding

What are Design Patterns?

Object Oriented Software Design

Commonly used in Object Oriented Languages

• Apex, Java, C#, Objective C

Reusable Solution Templates

• Not libraries

3 categories (from GoF)

• Creational – object creation

• Structural – relationships between objects

• Behavioural – communication between objects

Creational

Logic isolation

Centralize object creation logic

• Interface

• Class hierarchy

Factory Pattern

Structural

On behalf of the real object

• Hide details

• Optimization

• House keeping tasks

Proxy Pattern

Combine Proxy and Factory Patterns

Demo 1

Custom Settings

Custom Settings

Thin object

Promotes testingNo need to query

Configurable in real time

Store KVP

Application/Code Settings

List/Map containers

.getAll()

List vs. Hierarchy Custom Settings

User/Profile based

Global setting

One set of results

.getInstance()

List Type Hierarchy Type

Key Benefits

Manage change quickly

Configuration > Customization

Feature Toggles

Code Reuse

Schema Namespace

Runtime metadata query

Useful for Dynamic Apex

Get object configuration information

Special accessor methods

Demo 2

What is Dynamic Binding?

Compile-time vs Runtime

Tightly coupled vs. Loosely coupled

Classes vs. Interfaces

Types vs. Objects

System.Type Class

System.Type.forName(className: String)

Default constructor

Type casting, can be interface

Dependency Injection

public interface Animal {...}public class Cat implements Animal { public Cat(){…}// default constructor}System.Type sType = System.Type.forName('Cat'); // using apex-class name to get aTypeAnimal animal = (Animal) sType.newInstance(); // instantiate and cast to an interface

Back to the first demo…

Boilerplate code

Not easy to add a new version

• New code: service, & implementation classes

• Need to update permissions on new classes

Testing predefined scenarios

• Testing compile time logic

Problems Changes

Using custom settings to provide implementation details

Using System.Type to instantiate implementation

Using classes in Schema namespaces to create and query Salesforce objects

Testing runtime behaviour

• Setup test configuration

Demo 3

Summary

Dynamic Binding using Apex

• Runtime, Interfaces, Loosely Coupled

Custom Settings

• Hierarchical and List

Advance Apex Features

• System.Type and SObject classes

• Schema Namespace

Summary continues

Testing

• Interface driven

• Test classes can be used in custom setting

• Testing new scenarios

Other examples on using dynamic binding

• Fine grain security

• Extends Salesforce OOTB functions/features

• Trigger

References

Books:

• Design Patterns: Elements of Reusable Object-Oriented Software, Addison-Wesley

• Head First Design Patterns, O’Reilly

Links:

• Apex Design Patterns, Salesforce https://developer.salesforce.com/page/Apex_Design_Patterns

• Force.com Apex Code Developer's Guide https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/

Q & A

Thank you