WELCOME!• Name is: Joseph Maxwell

• Example code:

• https://github.com/JosephMaxwell/DesignPatterns

DESIGN PATTERNS• Borrowed from the building

industry.

• A means to label common and industry-tested architectural patterns.

"Joy Oil gas station blueprints" by Joy Oil Co Ltd - This image is available from the City of Toronto Archives, listed under the archival citation Series

410, File 505, Item 8.

DESIGN PATTERN BENEFITS

• Presents a common solution to a problem.

• Makes some problem solving more plug-and-play, thus writing code faster.

• Recognizable to other developers.

• Encourages more legible and maintainable code.

TERMINOLOGY• Interface:

• a means to provide an outline for a class. Classes must provide functionality to this outline.

• Abstract:

• a class that cannot be created, but must be extended.

• Concrete:

• an extension of a abstract class. Usually customize functionality.

FACTORYAllows centralization of code for class construction.

FACTORY• We don’t make our own

phones.

• A factory does.

• “A building or group of buildings where goods are manufactured or assembled chiefly by machine.” — Google

PROBLEM:• Infinite types of

products

• Don’t want to know what product is created

• Each product should bring their own functionality.

FACTORY DESIGN:

Model needs “Child Select” product

Factory

Simple Product

Child Select Product

Bundled Product

FACTORY SOLUTION:• Make a class to act as the factory.

• Force all classes instantiated to inherit a type or implement an interface.

• Return the newly created class.

• Best: use a configuration file (Yaml/Xml) to control the creation of the classes.

EXAMPLE

SIMPLEST FACTORY

FLEXIBLE SOLUTION:

YAML EXAMPLE:

USE CASES:• Assists with multiple types of different but

similar objects (products, image types, etc.).

• Gives means for allowing other developers to extend the functionality of your software.

TESTING:

SINGLETONSAnti-pattern: a global means to access one instance of an

object

PROBLEM:• Your class needs to interact

with a specific instance of another class.

• How do you create or access that specific instance throughout your class?

PROBLEM:

SINGLETON DESIGNModel needs

session

class Session

Create instance and store it.

self::$_instance? Return instance.

No

Yes

SOLUTION?• Use static class methods to track single

instance of object:

Using Static:

SINGLETON’S PROBLEMS:

• Hard links the session to the class.

• Makes testing difficult or impossible.

• Breaks Single Responsibility Principle managing its own instance.

DEPENDENCY INJECTION (DI)

Providing classes the variables they need.

Title Text

DI DESIGN

new Model(Session $session);

new Session();

DI• We create the objects and then “inject”

them into each class that needs it.

• Benefits:

• Easier to follow Single Responsibility Principle.

• Makes testing easier: we can inject a testing-tuned class.

• Good visibility into what each class needs.

DI

DI (MANUAL)

DI CONTAINERS

new Model(); new Session() DI Container

__construct(Session $session)

DI CONTAINERS• Pimple (pimple.sensiolabs.org)

• Super simple container but is rather manual.

• PHP-DI (http://php-di.org/)

• More complex to setup but injection is automatic.

• Similar to Symphony Dependency Injection

component: https://github.com/symfony/DependencyInjection

TESTING:

USE CASES:• Database connections

• Sessions

CHAIN OF RESPONSIBILITY

Handling logic through multiple layers of functionality.

PROBLEM:• Multiple layers of caching.

• How to get the value from the list?

• Multiple renderers for a component.

• How to have renderers determine who should render?

SOLUTION #1: LOOPS• Easier, but less flexible.

• Iterate through each member of an array of the items and have that member check to determine its legibility.

SOLUTION #1: LOOPS

SOLUTION #2: COR• More complex, but offers greater flexibility.

• Each layer inherits from an abstract object.

• Abstract object handles chaining.

• Concrete objects inherit abstract and provide functionality for processing and whether to proceed.

COR DESIGN

Need cache value

DBMemcachedRedis

processed? processed? processed?

No

Yes!

Base Object

TESTING:

USE CASES:• Layers of caching

• Rendering views with a standard input, but giving each member the equal opportunity to display.

REVIEW

Factory DI CoR

Chooses and creates object from

options.

Ensures object is only created once.

Interacts with options to retrieve

output.

All use specific class to maintain Single Responsibility Principle.

RESOURCES• Design Patterns: Elements of Reusable

Object-Oriented Software• (Gamma, Helm, Johnson, Vlissides; published by Addison-

Wesley)

• Design Patterns PHP• http://designpatternsphp.readthedocs.org/en/latest/

FEEDBACK?https://joind.in/14702