Practical Approach of Using Design Patterns

Design patterns are conceptual solutions to solve common redundant problems in software engineering. However, learning them is not easy as litterature or tutorials on the Internet often introduce them with theorical examples. This talk gives you a slightly different approach by introducing design patterns with practical code samples to solve real world problems. You won't just learn design patterns, you will also discover how to leverage them!

Transcript

1. Practical Approach of Using
   Design Patterns
   Confoo 2016 – Montréal - Hugo Hamon
   

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2. Hugo Hamon
   Head of training
   SensioLabs
   Book author
   Speaker at conferences
   5th time speaking at Confoo
   Symfony contributor
   Bengal cat lover
   @hhamon / @catlannister
   

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3. Introduction
   

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4. In software design, a
   design pattern is an
   abstract generic solution
   to solve a particular
   common problem.
   

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5. Patterns Families
   •  23 GoF Patterns
   •  Creational
   •  Structural
   •  Behavioral
   

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6. Pros of Design Patterns
   •  Team communication
   •  Testability
   •  Maintainance
   •  Extensibility
   •  Loose coupling
   

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7. Cons of Design Patterns
   •  Hard to learn
   •  Hard to find real world examples
   •  Hard to know when to apply
   •  Require good knowledge of OOP
   •  Not always the holly grail!
   

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8. Today’s talk focuses on
   the Factory Method,
   Decorator and
   Composite design
   patterns
   

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9. http://images.wisegeek.com/factory-with-pipes.jpg
   Factory Method
   

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10. Encapsulating the Creation
    of Objects
    
    Centralizing the way objects are created.
    

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11. The Factory object encapsulates the process for
    creating, assembling and initializing objects. It hides
    this whole process from the client code that just
    needs to get a new made object.
    The Need for a Factory
    Having a Factory also allows to change the process
    for creating objects at any time without impacting the
    client code.
    

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12. Real World Factories
    

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13. Why having factories?
    The car factory may want to change the steps to
    assemble a new car in order to reduce costs and generate
    more profits. In the end, the final customer still buys a
    functional car whatever ways it has been produced.
    The baker may want to slightly change the recipe of his
    bread to make more profits or improve quality. In the
    end, the customer still buys a « baguette » at the bakery.
    

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14. The Static & Simple
    Factories
    

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15. class MediaFactory
    {
    public static function createMedia($path)
    {
    $format = strtolower(pathinfo($path, PATHINFO_EXTENSION));
    if ('pdf' === $format) {
    return new PdfFile($path);
    }
    if (in_array($format, [ 'jpg', 'png', 'gif' ])) {
    return new ImageFile($path);
    }
    if ('txt' === $format) {
    return new TextFile($path);
    }
    throw new \UnexpectedValueException('Unexpected format '. $format);
    }
    }
    The Static Method Approach
    

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16. $file1 = MediaFactory::createMedia('/path/to/file.jpg'); // ImageFile
    $file2 = MediaFactory::createMedia('/path/to/file.png'); // ImageFile
    $file3 = MediaFactory::createMedia('/path/to/file.gif'); // ImageFile
    $file4 = MediaFactory::createMedia('/path/to/file.pdf'); // PdfFile
    $file5 = MediaFactory::createMedia('/path/to/file.txt'); // TextFile
    The Static Method Approach
    This snippet of code shows how different types of
    objects are created based on the given file path
    extension. The static factory method either returns
    an ImageFile, or a PdfFile or a TextFile object.
    

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17. class DocumentRepository
    {
    private $filesystem;
    private $imageManipulator;
    function __construct(Filesystem $filesystem, ImageManipulator $manipulator)
    {
    $this->filesystem = $filesystem;
    $this->imageManipulator = $nanipulator;
    }
    public function move($path, $target)
    {
    $file = MediaFactory::createMedia($path);
    if ($file instanceof ImageFile) {
    $file = $this->imageManipulator->resize($file, 120, 120);
    }
    $this->filesystem->move($file->getRealPath(), $target);
    }
    }
    The Static Method in Action
    

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18. Pros & Cons of the Static Method
    •  Tight coupling between the factory and the client,
    •  Client code is more difficult to unit test,
    •  Unable to switch to another factory,
    •  Difficulty to rely on dependencies in the factory.
    •  Very simple,
    •  Very pragmatic,
    •  Easy to understand.
    

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19. class MediaFactory implements MediaFactoryInterface
    {
    public function createMedia($path)
    {
    $format = strtolower(pathinfo($path, PATHINFO_EXTENSION));
    if ('pdf' === $format) {
    return new PdfFile($path);
    }
    if (in_array($format, [ 'jpg', 'png', 'gif' ])) {
    return new ImageFile($path);
    }
    if ('txt' === $format) {
    return new TextFile($path);
    }
    throw new \UnexpectedValueException('Unexpected format '. $format);
    }
    }
    The Simple Factory Approach
    

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20. $factory = new MediaFactory();
    $file1 = $factory->createMedia('/path/to/file.jpg'); // ImageFile
    $file2 = $factory->createMedia('/path/to/file.png'); // ImageFile
    $file3 = $factory->createMedia('/path/to/file.gif'); // ImageFile
    $file4 = $factory->createMedia('/path/to/file.pdf'); // PdfFile
    $file5 = $factory->createMedia('/path/to/file.txt'); // TextFile
    The Simple Factory Approach
    This snippet of code shows how different types of objects
    are created based on the given file path extension. The
    factory is now an instance with a method that either returns
    an ImageFile, or PdfFile or TextFile object.
    

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21. class DocumentRepository
    {
    private $mediaFactory;
    // ...
    public function __construct(
    FilesystemInterface $filesystem,
    MediaFactoryInterface $mediaFactory,
    ImageManipulatorInterface $imageManipulator
    )
    {
    $this->filesystem = $filesystem;
    $this->mediaFactory = $mediaFactory;
    $this->imageManipulator = $imageManipulator;
    }
    public function move($path, $target)
    {
    $file = $this->mediaFactory->createMedia($path);
    // ...
    }
    }
    The Simple Factory in Action
    

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22. Pros & Cons of the Simple Factory
    •  It’s still not a real factory method object.
    •  The factory produces multiple kinds of objects.
    •  Simple & pragmatic approach.
    •  Loose coupling between factory and client code.
    •  Uses dependency injection.
    •  Easy to unit test the client code.
    •  Easy to replace the actual factory by another one.
    

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23. The Real Factory
    Method Pattern
    

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24. The Factory Method
    Creational pattern
    
    •  Encapsulate the creation of an object
    •  Algorithm to create object is partially implemented
    •  Object creation is delegated to subclasses
    •  Client code doesn’t know the type of the created object
    •  Each factory creates one kind of object
    

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25. UML Diagram
    

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26. Media Gallery
    System
    Example
    

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27. Diagram for Media Metadata Factories
    

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28. namespace MediaGallery;
    interface MediaMetadataFactoryInterface
    {
    /**
    * Loads the metadata of a given multimedia file.
    *
    * @param string $path The multimedia file path
    *
    * @return MediaMetadataInterface $metadata
    * @throws MediaNotFoundException
    */
    public function loadMetadata($path);
    }
    The Abstract Metadata Factory
    

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29. namespace MediaGallery\Metadata;
    use MediaGallery\Analyzer\MediaAnalyzerInterface;
    use MediaGallery\MediaMetadataFactoryInterface;
    use MediaGallery\MediaMetadataInterface;
    use MediaGallery\MediaNotFoundException;
    abstract class MediaMetadataFactory implements MediaMetadataFactoryInterface
    {
    private $analyzer;
    public function __construct(MediaAnalyzerInterface $analyzer)
    {
    $this->analyzer = $analyzer;
    }
    abstract protected function createMetadata(\SplFileInfo $file);
    protected function analyze(\SplFileInfo $file)
    {
    return $this->analyzer->analyze($file);
    }
    }
    The Abstract Metadata Factory
    

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30. abstract class MediaMetadataFactory implements MediaMetadataFactoryInterface
    {
    // ...
    /** @return MediaMetada */
    public function loadMetadata($path)
    {
    if (!is_readable($path)) {
    throw new MediaNotFoundException(sprintf('%s not readable.', $path));
    }
    $file = new \SplFileInfo($path);
    $metadata = $this->createMetadata($file);
    $metadata->initialize($file);
    return $metadata;
    }
    }
    The Abstract Metadata Factory
    

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31. The Abstract MediaMetada Class
    The abstract MediaMetadata class is designed to
    encapsulate the common shared attributes by all
    media files types.
    For each media file, it stores its real path, its size
    and its creation date on the filesystem.
    

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32. namespace MediaGallery\Metadata;
    use MediaGallery\MediaMetadataInterface;
    abstract class MediaMetadata implements MediaMetadataInterface
    {
    private $realPath;
    private $size;
    private $createdAt;
    public function initialize(\SplFileInfo $file)
    {
    $this->size = $file->getSize();
    $this->realPath = $file->getRealPath();
    $this->createdAt = $file->getMTime();
    }
    // … plus one getter for each private property
    }
    The Abstract MediaMetadata Class
    

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33. The Image Metadata Factory
    The ImageMetadataFactory class is responsible for
    producing ImageMetadata objects. To analyze a picture,
    the factory uses an ImageAnalyzer instance.
    Each ImageMetadata instance has a real path, a size, a
    creation date but also a set of dimensions (width & height)
    and an orientation (portrait, landscape or square).
    

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34. namespace MediaGallery\Metadata;
    class ImageMetadata extends MediaMetadata
    {
    const SQUARE = 'square';
    const PORTRAIT = 'portrait';
    const LANDSCAPE = 'landscape';
    private $width;
    private $height;
    public function __construct($width, $height)
    {
    $this->width = (int) $width;
    $this->height = (int) $height;
    }
    // … plus getter methods
    }
    The ImageMetadata Class
    

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35. namespace MediaGallery\Analyzer;
    class ImageAnalyzer implements MediaAnalyzerInterface
    {
    public function analyze(\SplFileInfo $file)
    {
    $path = $file->getRealPath();
    if (!$path || !$metadata = @getimagesize($path)) {
    throw new AnalysisFailedException(sprintf(
    'Unable to extract image metadata for path %s.',
    $path
    ));
    }
    return [ 'width' => $metadata[0], 'height' => $metadata[1] ];
    }
    }
    The ImageAnalyzer Class
    

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36. namespace MediaGallery\Metadata;
    class ImageMetadataFactory extends MediaMetadataFactory
    {
    /**
    * Creates the specific ImageMetadata object.
    *
    * @param \SplFileInfo $file
    * @return ImageMetadata
    */
    protected function createMetadata(\SplFileInfo $file)
    {
    $infos = $this->analyze($file);
    return new ImageMetadata($infos['width'], $infos['height']);
    }
    }
    The ImageMetadaFactory Class
    

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37. use MediaGallery\Analyzer\ImageAnalyzer;
    use MediaGallery\Metadata\ImageMetadataFactory;
    $factory = new ImageMetadataFactory(new ImageAnalyzer());
    $metadata = $factory->loadMetadata('/path/to/image.png');
    echo 'Path: ', $metadata->getRealPath() ,"\n";
    echo 'Date: ', $metadata->getCreatedAt() ,"\n";
    echo 'Size: ', $metadata->getSize() ,"\n";
    echo 'Width: ', $metadata->getWidth() ," px\n";
    echo 'Height: ', $metadata->getHeight() ," px\n";
    echo 'Orientation: ', $metadata->getOrientation() ,"\n";
    Using the Image Metada Factory
    

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38. The Movie Metadata Factory
    The MovieMetadataFactory class is responsible for
    producing MovieMetadata objects. To analyze a video
    clip, the factory uses an VideoAnalyzer instance.
    Each MovieMetadata instance has a real path, a size,
    a creation date but also a set of specific attributes: a
    resolution in pixels (x & y axis), a duration, a frame rate
    and a frame count.
    

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39. namespace MediaGallery\Metadata;
    class MovieMetadata extends MediaMetadata
    {
    private $xResolution;
    private $yResolution;
    private $frameRate;
    private $frameCount;
    private $duration;
    function __construct($xResolution, $yResolution, $duration, $frameRate, $frameCount)
    {
    $this->xResolution = (int) $xResolution;
    $this->yResolution = (int) $yResolution;
    $this->frameRate = (int) round($frameRate);
    $this->frameCount = (int) $frameCount;
    $this->duration = (int) round($duration);
    }
    // ... getters for all attributes
    }
    The MovieMetadata Class
    

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40. namespace MediaGallery\Analyzer;
    class VideoAnalyzer extends AudioVideoAnalyzer
    {
    public function analyze(\SplFileInfo $file)
    {
    $metadata = $this->extractMetadata($file->getRealPath());
    $format = $metadata['video']['dataformat'];
    return [
    'resolution_x' => $metadata['video']['resolution_x'],
    'resolution_y' => $metadata['video']['resolution_y'],
    'duration' => $metadata['playtime_seconds'],
    'frame_rate' => $metadata['video']['frame_rate'],
    'frame_count' => $metadata[$format]['video']['frame_count'],
    ];
    }
    }
    The VideoAnalyzer Class
    

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41. namespace MediaGallery\Metadata;
    class MovieMetadataFactory extends MediaMetadataFactory
    {
    protected function createMetadata(\SplFileInfo $file)
    {
    // The $metadata is filled with information
    // provided by the awesome GetId3Core class
    // from the eponym library
    $metadata = $this->analyze($file);
    return new MovieMetadata(
    $metadata['resolution_x'],
    $metadata['resolution_y'],
    $metadata['duration'],
    $metadata['frame_rate'],
    $metadata['frame_count']
    );
    }
    }
    The MovieMetadataFactory Class
    

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42. use MediaGallery\Analyzer\VideoAnalyzer;
    use MediaGallery\Metadata\MovieMetadataFactory;
    $factory = new MovieMetadataFactory(new VideoAnalyzer());
    $metadata = $factory->loadMetadata('/path/to/movie.mp4');
    echo 'Path: ', $metadata->getRealPath() ,"\n";
    echo 'Date: ', $metadata->getCreatedAt() ,"\n";
    echo 'Size: ', $metadata->getSize() ,"\n";
    echo 'Resolution X: ', $metadata->getXResolution() ,' px ', "\n";
    echo 'Resolution Y: ', $metadata->getYResolution() ,' px ', "\n";
    echo 'Duration: ', $metadata->getDuration() ," seconds\n";
    echo 'Frame rate: ', $metadata->getFrameRate() ," fps\n";
    echo 'Frames: ', $metadata->getFrameCount() ," frames\n";
    Using the Movie Metadata Factory
    

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43. Composite
    

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44. Processing Single Objects
    & Collections Uniformly
    
    Sharing a unified interface.
    

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45. The Composite
    Structural pattern
    •  Treating single objects and collections uniformly.
    •  Sharing a unified interface.
    •  Combining objects easily.
    •  Processing recursiving operations on objects.
    

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46. UML Diagram
    

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47. Composite Usage
    $nestedComposite = new ConcreteComposite();
    $nestedComposite->add(new ConcreteLeaf());
    $nestedComposite->add(new ConcreteLeaf());
    $composite = new ConcreteComposite();
    $composite->add(new ConcreteLeaf());
    $composite->add(new ConcreteLeaf());
    $composite->add($nestedComposite);
    $composite->operation();
    $leaf = new ConcreteLeaf();
    $leaf->operation();
    

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48. Use Cases For a Composite
    •  File explorer
    •  Organization chart
    •  Family tree
    •  Content management (nested pages)
    •  XML file parsing
    •  Nested web forms
    •  Navigation bar (items including subitems)
    •  …
    

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49. Implementing the
    Composite Pattern
    

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50. Single & Combo Products
    •  The goal is to sell single products and combos.
    •  Each product can be either physical / digital or a combo.
    •  Unless physical products, digital ones don’t have a mass.
    •  The unit price belongs to each product.
    •  Combo products can have a fixed or dynamic price.
    •  Combo’s total weight is always the sum of its combined products.
    

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51. UML Diagram
    

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52. namespace Shop;
    interface ProductInterface
    {
    public function getName();
    /** @return \Sebastian\Money\Money */
    public function getPrice();
    /** @return \Physics\Metrics\Mass */
    public function getMass();
    }
    The Product Interface
    

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53. namespace Shop;
    use Physics\Metrics\Mass;
    use SebastianBergmann\Money\Money;
    abstract class Product implements ProductInterface
    {
    protected $name;
    protected $price;
    protected $mass;
    public function __construct($name, Money $price, Mass $mass)
    {
    $this->name = $name;
    $this->price = $price;
    $this->mass = $mass;
    }
    public function getPrice()
    {
    return $this->price;
    }
    }
    The Abstract Product Class
    

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54. namespace Shop;
    abstract class Product implements ProductInterface
    {
    // ...
    public function getName()
    {
    return $this->name;
    }
    public function getMass()
    {
    return $this->mass;
    }
    }
    The Abstract Product Class
    

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55. namespace Shop;
    class HardProduct extends Product
    {
    }
    The Product Concrete Classes
    namespace Shop;
    use Physics\Metrics\Mass;
    use SebastianBergmann\Money\Money;
    class DigitalProduct extends Product
    {
    public function __construct($name, Money $price)
    {
    parent::__construct($name, $price, new Mass(0));
    }
    }
    

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56. $paperBook = new HardProduct(
    'PHP 5 Design Patterns',
    Money::fromString('49.00', 'EUR'),
    Mass::fromString('960.00 g')
    );
    $digitalBook = new DigitalProduct(
    'PHP 5 Design Patterns',
    Money::fromString('22.00', 'EUR')
    );
    Creating Physical & Digital Products
    

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57. namespace Shop;
    use SebastianBergmann\Money\Money;
    class Combo extends Product
    {
    private $products;
    function __construct($name, array $products, Money $price = null)
    {
    $this->setProducts($products);
    parent::__construct($name, $price ?: $this->getTotalPrice(), $this->getTotalMass());
    }
    // ...
    private function add(ProductInterface $product)
    {
    $this->products[] = $product;
    }
    }
    The Combo Concrete Class
    

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58. class Combo extends Product
    {
    // ...
    private function setProducts(array $products)
    {
    if (count($products) < 2) {
    throw new \LogicException('At least 2 items required.');
    }
    foreach ($products as $product) {
    $this->add($product);
    }
    }
    }
    The Combo Concrete Class
    

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59. class Combo extends Product
    {
    // ...
    private function getTotalPrice()
    {
    $total = $this->getPriceAt(0);
    for ($i = 1; $i < count($this->products); $i++) {
    $total = $total->add($this->getPriceAt($i));
    }
    return $total;
    }
    private function getPriceAt($index)
    {
    return $this->get($index)->getPrice();
    }
    private function get($index)
    {
    return $this->products[$index];
    }
    }
    Get Combo Total Price
    

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60. class Combo extends Product
    {
    // ...
    private function getTotalMass()
    {
    $total = $this->getMassAt(0);
    for ($i = 1; $i < count($this->products); $i++) {
    $total = $total->add($this->getMassAt($i));
    }
    return $total;
    }
    private function getMassAt($index)
    {
    return $this->get($index)->getMass();
    }
    }
    Get Combo Total Mass
    

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61. $products = [
    new HardProduct('Digital Camera', new EUR(78900), new Mass(855)),
    new HardProduct('Camera Bag', new EUR(3900), new Mass(220)),
    new HardProduct('Memory Card 128 Gb', new EUR(7900), new Mass(42)),
    ];
    $combo = new Combo('Digital Camera & Bag', $products, new EUR(83900));
    echo 'Name: ', $combo->getName() ,"\n";
    echo 'Mass: ', $combo->getMass()->getValue() ," g\n";
    echo 'Price: ', $combo->getPrice()->getAmount() ," €\n";
    The Combo with a Fixed Price
    Name: Digital Camera & Bag
    Mass: 1117 g
    Price: 83900 €
    

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62. $products = [
    new HardProduct('Digital Camera', new EUR(78900), new Mass(855)),
    new HardProduct('Camera Bag', new EUR(3900), new Mass(220)),
    new HardProduct('Memory Card 128 Gb', new EUR(7900), new Mass(42)),
    ];
    $combo = new Combo('Digital Camera & Bag', $products);
    echo 'Name: ', $combo->getName() ,"\n";
    echo 'Mass: ', $combo->getMass()->getValue() ,"\n";
    echo 'Price: ', $combo->getPrice()->getAmount() ,"\n";
    The Combo with a Dynamic Price
    Name: Digital Camera & Bag
    Mass: 1117 g
    Price: 90700 €
    

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63. $products = [
    new HardProduct('Digital Camera', new EUR(78900), new Mass(855)),
    new HardProduct('Camera Bag', new EUR(3900), new Mass(220)),
    new HardProduct('Memory Card 128 Gb', new EUR(7900), new Mass(42)),
    ];
    $combo = new Combo('Digital Camera Combo Pack + Tripod', [
    new HardProduct('Lightweight Tripod', new EUR(2690), new Mass(570)),
    new Combo('Digital Camera & Bag', $products, new EUR(83900)),
    ]);
    echo 'Name: ', $combo->getName() ,"\n";
    echo 'Weight: ', $combo->getWeight()->getValue() ,"\n";
    echo 'Price: ', $combo->getPrice()->getAmount() ,"\n";
    The Super Dupper Combo!
    Name: Digital Camera Combo Pack + Tripod
    Mass: 1687 g
    Price: 86590 €
    

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64. Decorator
    

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65. Composition over
    Inheritance
    
    Extending objects at will!
    

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66. The Decorator
    Structural pattern
    •  Adding new responsabilities to an object
    •  Don’t break / change the existing API
    •  Use composition over inheritance
    •  Allow infinite responsabilities combinations
    •  Respect SOLID principle
    

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68. Decorator Usage
    $instance = new OtherConcreteDecorator(
    new SomeConcreteDecorator(
    new ConcreteDecorator(
    new DecoratedComponent()
    )
    )
    );
    $instance->operation();
    

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69. StackPHP Middlewares
    http://stackphp.com/
    

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70. Orders &
    Coupons
    Decorator Implementation
    

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71. Coupon Codes
    •  We want to offer discount codes to customers.
    •  Each discount can be value (-5 EUR) or rate (-10%) based.
    •  Coupon codes must be combinable.
    •  Each coupon is applicable upon certain conditions.
    •  There must be no limits inventing new coupon codes.
    •  Coupons reduce an Order’s total amount.
    

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72. Coupon Restrictions
    •  Valid for a specific period of time,
    •  Minimum total amount required,
    •  Minimum quantity of ordered items required,
    •  Valid for a specific geographical area,
    •  Customer must own the loyalty membership card,
    •  Coupon is valid for Premium / VIP customers only,
    •  Valid for the customer’s very first order,
    •  Some products are not eligible for discounts,
    •  Valid only on some specific products areas (luxury, food…),
    •  etc.
    

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73. UML Diagram
    

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74. namespace Shop\Discount;
    use SebastianBergmann\Money\Money;
    use Shop\OrderableInterface;
    interface CouponInterface
    {
    public function getCode();
    /**
    * Returns the new total amount after the coupon has been
    * applied on the given order.
    *
    * @param OrderableInterface $order The order to discount
    * @return Money The new order total amount
    * @throws CouponException When coupon is not applicable
    */
    public function applyDiscount(OrderableInterface $order);
    }
    The Coupon Interface
    

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75. namespace Shop\Discount;
    use SebastianBergmann\Money\Money;
    use Shop\OrderableInterface;
    class ValueCoupon implements CouponInterface
    {
    private $code;
    private $discount;
    public function __construct($code, Money $discount)
    {
    $this->code = $code;
    $this->discount = $discount;
    }
    public function getCode()
    {
    return $this->code;
    }
    public function applyDiscount(OrderableInterface $order)
    {
    return $order->getTotalAmount()->subtract($this->discount);
    }
    }
    The ValueCoupon Class
    

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76. namespace Shop\Discount;
    use Shop\OrderableInterface;
    class RateCoupon implements CouponInterface
    {
    private $code;
    private $rate;
    public function __construct($code, $rate)
    {
    if (!is_float($rate)) {
    throw new \InvalidArgumentException('$rate must be a float.');
    }
    if ($rate <= 0 || $rate > 1){
    throw new \InvalidArgumentException('$rate must be in ]0, 1].');
    }
    $this->code = $code;
    $this->rate = $rate;
    }
    }
    The RateCoupon Class
    

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77. namespace Shop\Discount;
    use Shop\OrderableInterface;
    class RateCoupon implements CouponInterface
    {
    // ...
    public function getCode()
    {
    return $this->code;
    }
    public function applyDiscount(OrderableInterface $order)
    {
    $amount = $order->getTotalAmount();
    return $amount->subtract($amount->multiply($this->rate));
    }
    }
    The RateCoupon Class
    

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78. namespace Shop\Discount;
    abstract class CouponDecorator implements CouponInterface
    {
    protected $coupon;
    public function __construct(CouponInterface $coupon)
    {
    $this->coupon = $coupon;
    }
    public function getCode()
    {
    return $this->coupon->getCode();
    }
    protected function createCouponException($message, \Exception $previous = null)
    {
    return new CouponException($message, 0, $previous);
    }
    }
    The Abstract CouponDecorator Class
    

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79. namespace Shop\Discount;
    use Shop\OrderableInterface;
    class LimitedLifetimeCoupon extends CouponDecorator
    {
    private $startAt;
    private $expiresAt;
    public function __construct(CouponInterface $coupon, $startAt, $expiresAt)
    {
    if (!$startAt instanceof \DateTime) {
    $startAt = new \DateTime($startAt);
    }
    if (!$expiresAt instanceof \DateTime) {
    $expiresAt = new \DateTime($expiresAt);
    }
    if ($startAt > $expiresAt) {
    throw new \InvalidArgumentException('$startAt cannot be greater than $expiresAt.');
    }
    parent::__construct($coupon);
    $this->startAt = $startAt;
    $this->expiresAt = $expiresAt;
    }
    }
    The LimitedLifetimeCoupon Decorator Class
    

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80. class LimitedLifetimeCoupon extends CouponDecorator
    {
    public function applyDiscount(OrderableInterface $order)
    {
    $now = new \DateTime('now');
    if ($this->startAt > $now) {
    throw $this->createCouponException(sprintf(
    'Coupon is usable from %s.',
    $this->startAt->format('Y-m-d H:i:s')
    ));
    }
    if ($now > $this->expiresAt) {
    throw $this->createCouponException(sprintf(
    'Coupon was valid until %s.',
    $this->expiresAt->format('Y-m-d H:i:s')
    ));
    }
    return $this->coupon->applyDiscount($order);
    }
    }
    The LimitedLifetimeCoupon Decorator Class
    

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81. use SebastianBergmann\Money\Money;
    use Shop\Discount\LimitedLifetimeCoupon;
    use Shop\Discount\RateCoupon;
    use Shop\Discount\ValueCoupon;
    // Coupon offers a discount value of 20 €.
    $coupon1 = new LimitedLifetimeCoupon(
    new ValueCoupon('3s2h7pd65s', Money::fromString('20.00', EUR')),
    '2014-05-01',
    '2014-08-31'
    );
    // Coupon offers 25% off.
    $coupon2 = new LimitedLifetimeCoupon(
    new RateCoupon('76cqa6qr19', 0.25),
    '2014-05-01',
    '2014-08-31'
    );
    The LimitedLifetimeCoupon Decorator Class
    

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82. namespace Shop\Discount;
    use SebastianBergmann\Money\Money;
    use Shop\OrderableInterface;
    class MinimumPurchaseAmountCoupon extends CouponDecorator
    {
    private $minimumAmount;
    function __construct(CouponInterface $coupon, Money $minAmount)
    {
    parent::__construct($coupon);
    $this->minimumAmount = $minAmount;
    }
    }
    The MinimumPurchaseAmountCoupon Decorator Class
    

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83. class MinimumPurchaseAmountCoupon extends CouponDecorator
    {
    public function applyDiscount(OrderableInterface $order)
    {
    $amount = $order->getTotalAmount();
    if ($amount->lessThan($this->minimumAmount)) {
    throw $this->createCouponException(sprintf(
    'Coupon requires a minimum amount of %u.',
    $this->minimumAmount->getAmount()
    ));
    }
    return $this->coupon->applyDiscount($order);
    }
    }
    The MinimumPurchaseAmountCoupon Decorator Class
    

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84. use SebastianBergmann\Money\Money;
    use Shop\Discount\MinimumPurchaseAmountCoupon;
    use Shop\Discount\RateCoupon;
    use Shop\Discount\ValueCoupon;
    // Get 20 € off if total amount is greater than 300 €
    $coupon1 = new MinimumPurchaseAmountCoupon(
    new ValueCoupon('3s2h7pd65s', Money::fromString('20.00', EUR')),
    Money::fromString('300.00', EUR')
    );
    // Get 25% off if total amount is greater than 300 €
    $coupon2 = new MinimumPurchaseAmountCoupon(
    new RateCoupon('76cqa6qr19', 0.25),
    Money::fromString('300.00', EUR')
    );
    The MinimumPurchaseAmountCoupon Decorator Class
    

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85. namespace Shop\Discount;
    use Shop\OrderableInterface;
    class CustomerFirstOrderCoupon extends CouponDecorator
    {
    public function applyDiscount(OrderableInterface $order)
    {
    $customer = $order->getCustomer();
    if ($customer->hasPastOrders()) {
    throw $this->createCouponException(
    'Customer already has past orders.’
    );
    }
    return $this->coupon->applyDiscount($order);
    }
    }
    The CustomerFirstOrderCoupon Decorator Class
    

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86. use SebastianBergmann\Money\Money;
    use Shop\Discount\CustomerFirstOrderCoupon;
    use Shop\Discount\RateCoupon;
    use Shop\Discount\ValueCoupon;
    // Get 20 € off on the first order
    $coupon1 = new CustomerFirstOrderCoupon(
    new ValueCoupon(
    '3s2h7pd65s',
    Money::fromString('20.00', EUR')
    )
    );
    // Get 25% off on the first order
    $coupon2 = new CustomerFirstOrderCoupon(
    new RateCoupon('76cqa6qr19', 0.25)
    );
    The CustomerFirstOrderCoupon Decorator Class
    

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87. use SebastianBergmann\Money\Money;
    use Shop\Discount\ValueCoupon;
    use Shop\Discount\LimitedLifetimeCoupon;
    use Shop\Discount\MinimumPurchaseAmountCoupon;
    use Shop\Discount\CustomerFirstOrderCoupon;
    // Create the special coupon
    $coupon = new ValueCoupon('3s2h7pd65s', Money::fromString('20.00', 'EUR'));
    $coupon = new LimitedLifetimeCoupon($coupon, 'now', '+60 days');
    $coupon = new MinimumPurchaseAmountCoupon($coupon, Money::fromString('170.00', 'EUR'));
    $coupon = new CustomerFirstOrderCoupon($coupon);
    // Create the order instance
    $customer = new \Shop\Customer('jsmith@example.com');
    $order = new \Shop\Order($customer, Money::fromString('200.00', 'EUR'));
    // Apply discount coupon on the order
    $discountedAmount = $coupon->applyDiscount($order);
    Multiple Restrictions Coupon
    

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88. Thank You!
    Questions?
    Confoo 2016 – Montréal - Hugo Hamon
    

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