Strategy Pattern for PHP and Symfony2
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README.markdown

Godfather

godfather A library for the strategy pattern in PHP, if you use Symfony2 you could easily integrate Godfather with the bundle.
  1. The Strategy pattern
  2. Installation
  3. Symfony2 bundle
  4. Contribution

travis-ci Latest Stable Version Total Downloads Latest Unstable Version


The Strategy Pattern

http://en.wikipedia.org/wiki/Strategy_pattern

Intent

Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it.

TL;DR

Given an object, you want to know its service.

eg. Entity\Mug has a MugService and Entity\Tshirt has a TshirtService

$product = random(0,1)? new Entity\Mug: new Entity\Product
$productService = $godfather->getStrategy('service', $product);
// also works with
$productService = $godfather->getService($product);
echo get_class($productService);
// will be randomly TshirtService or MugService

Sandbox

A working example is at example/godfather.php

cd example
php godfather.php

When do you need a strategist as Godfather?

  • If you have a lot of classes that differs by their behaviour...
  • If you have multiple conditional statements in order to define different behaviours...
  • Given an object you want to know its manager/service/handler/provider/repository/...

Installation

composer require pugx/godfather ~0.1

A simple use case

The problem is that you have an object and you want to handle it properly.

How it works

This library does not try to duplicate the services, or to create a new container, but uses aliases in order to have a mapping between services and names.

An object is converted by the Context::getStrategyName more info at changing the Context::Converter.

The smelling code

If your code look like this you will need the godfather's protection :)

// Pseudo Code
class Cart
  function add(ProductInterface $product, OptionsInterface $options)
  {
    if ($product instanceOf Mug) {
        $item = $mugManager->add($options);
    }
    if ($product instanceOf Tshirt) {
        $item = $tshirtManager->add($options);
    }
    // ...
 }

The strategist

// Pseudo Code
class Cart
  function add(ProductInterface $product, OptionsInterface $options)
  {
    $item = $this->godfather->getManager($product)->add($options);
    // ...
 }

GodFather and an array as DIC

$container =  new Container\ArrayContainerBuilder();
$container->set('mug_service', new Your\MugService);
$container->set('tshirt_service', new Your\TshirtService);

$godfather = new Godfather($container, 'godfather');

$godfather->addStrategy('service', 'Mug', 'mug_service');
$godfather->addStrategy('service', 'Tshirt', 'tshirt_service');


// Step2. usage
class Cart
  public function __construct($godfather)
  //...
  public function add(ProductInterface $product, OptionsInterface $options)
  {
    // get the strategy for cart with the context $product
    $service = $this->godfather->getStrategy('service', $product);
    // or $strategy = $this->godfather->getCart($product);

    return $strategy->addToCart($product, $options);
 }

GodFather and Symfony Dependency Injection Container

$container =  new Container\ArrayContainerBuilder();
$loader = new Loader\XmlFileLoader($container, new FileLocator(__DIR__ . '/../Resources/config'));
$loader->load('services.xml');

$godfather = new Godfather($container, 'godfather');

// Step2. usage
class Cart
  public function __construct($godfather)
  //...
  public function add(ProductInterface $product, OptionsInterface $options)
  {
    // get the strategy for cart with the context $product
    $service = $this->godfather->getStrategy('service', $product);
    // or $strategy = $this->godfather->getService($product);

Using the Symfony2 Bundle

Install the Bundle

Add the bundle in the app/AppKernel.php

class AppKernel extends Kernel
{
    public function registerBundles()
    {
        $bundles = array(
            ...
            new PUGX\GodfatherBundle\GodfatherBundle(),

Configuring app/config/config.yml

Minimal Configuration

# add the below configuration only if you need to specify the fallback or the interface.
godfather:
    default:
        contexts:
            manager: ~ # your strategy name

With the fallback strategy

# add the below configuration only if you need to specify the fallback or the interface.
godfather:
    default:
        contexts:
            manager:
                fallback: manager_standard  # need a reference to a defined service

Set your strategies:

parameters:
    mug.class: Mug
    tshirt.class: Tshirt

services:
    manager_standard:
        class: StandardProductManager

    manager_mug:
        class: MugManager
        tags:
            -  { name: godfather.strategy, context_name: 'manager', context_key: %mug.class% }

    manager_tshirt:
        class: TshirtManager
        tags:
            -  { name: godfather.strategy, context_name: 'manager', context_key: %tshirt.class% }

Using in the controller:

$product = new \Product\ShoeProduct();
$manager = $container->get('godfather')->getManager($product);
// or $manager = $container->get('godfather')->getStrategy('manager', $product);

// then $manager->doSomethingGreat();

Advanced with multiple instances

Instead of default you could configure your strategy in different godfather instances.

godfather:
    death:
        contexts:
            manager: ~
    life:
        contexts:
            manager: ~

the strategies:

services:
    manager.entity_life:
        class: EntityProductManager
        arguments:    ['life']
        tags:
        -  { name: godfather.strategy, instance:'life', context_name: 'manager', context_key: %product.show.class% }

    manager.entity_death:
        class: EntityProductManager
        arguments:    ['death']
        tags:
        -  { name: godfather.strategy, instance:'death', context_name: 'manager', context_key: %product.show.class% }

and then the code with multiple instances

$this->getContainer('godfather.life')->getManager($entity);
$this->getContainer('godfather.death')->getManager($entity);

Changing the Context::Converter

The Godfather\Context\Context::getStrategyName transforms an object into a strategy name, the default one just extract from the $object the short class name.

If you want another converter create your class extends the ContextInterface and then:

godfather:
    deafault:
        contexts:
            manager:
                class: \My\Context

Contribution

Active contribution and patches are very welcome. To keep things in shape we have quite a bunch of unit tests. If you're submitting pull requests please make sure that they are still passing and if you add functionality please take a look at the coverage as well it should be pretty high :)

composer create-project pugx/godfather --dev -s dev
cd godfather
bin/phpunit

License

The license is visible here.