PHP7 Flyweight

Author: Dominik Liebler

Structural/Flyweight/CharacterFlyweight.php

@@ -16,22 +16,16 @@ class CharacterFlyweight implements FlyweightInterface
      */
     private $name;
 
-    /**
-     * @param string $name
-     */
-    public function __construct($name)
+    public function __construct(string $name)
     {
         $this->name = $name;
     }
 
-    /**
-     * Clients supply the context-dependent information that the flyweight needs to draw itself
-     * For flyweights representing characters, extrinsic state usually contains e.g. the font.
-     *
-     * @param string $font
-     */
-    public function draw($font)
+    public function render(string $font): string
     {
-        print_r("Character {$this->name} printed $font \n");
+         // Clients supply the context-dependent information that the flyweight needs to draw itself
+         // For flyweights representing characters, extrinsic state usually contains e.g. the font.
+
+        return sprintf('Character %s with font %s', $this->name, $font);
     }
 }

Structural/Flyweight/FlyweightFactory.php

@@ -3,38 +3,26 @@
 namespace DesignPatterns\Structural\Flyweight;
 
 /**
- * A factory manages shared flyweights. Clients shouldn't instaniate them directly,
+ * A factory manages shared flyweights. Clients should not instantiate them directly,
  * but let the factory take care of returning existing objects or creating new ones.
  */
-class FlyweightFactory
+class FlyweightFactory implements \Countable
 {
     /**
-     * Associative store for flyweight objects.
-     *
-     * @var array
+     * @var CharacterFlyweight[]
      */
-    private $pool = array();
+    private $pool = [];
 
-    /**
-     * Magic getter.
-     *
-     * @param string $name
-     *
-     * @return Flyweight
-     */
-    public function __get($name)
+    public function get(string $name): CharacterFlyweight
     {
-        if (!array_key_exists($name, $this->pool)) {
+        if (!isset($this->pool[$name])) {
             $this->pool[$name] = new CharacterFlyweight($name);
         }
 
         return $this->pool[$name];
     }
 
-    /**
-     * @return int
-     */
-    public function totalNumber()
+    public function count(): int
     {
         return count($this->pool);
     }

Structural/Flyweight/FlyweightInterface.php

@@ -2,13 +2,7 @@
 
 namespace DesignPatterns\Structural\Flyweight;
 
-/**
- * An interface through which flyweights can receive and act on extrinsic state.
- */
 interface FlyweightInterface
 {
-    /**
-     * @param string $extrinsicState
-     */
-    public function draw($extrinsicState);
+    public function render(string $extrinsicState): string;
 }

Structural/Flyweight/Tests/FlyweightTest.php

@@ -4,33 +4,28 @@
 
 use DesignPatterns\Structural\Flyweight\FlyweightFactory;
 
-/**
- * FlyweightTest demonstrates how a client would use the flyweight structure
- * You don't have to change the code of your client.
- */
 class FlyweightTest extends \PHPUnit_Framework_TestCase
 {
-    private $characters = array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k',
-        'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', );
-    private $fonts = array('Arial', 'Times New Roman', 'Verdana', 'Helvetica');
-
-    // This is about the number of characters in a book of average length
-    private $numberOfCharacters = 300000;
+    private $characters = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k',
+        'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'];
+    private $fonts = ['Arial', 'Times New Roman', 'Verdana', 'Helvetica'];
 
     public function testFlyweight()
     {
         $factory = new FlyweightFactory();
 
-        for ($i = 0; $i < $this->numberOfCharacters; $i++) {
-            $char = $this->characters[array_rand($this->characters)];
-            $font = $this->fonts[array_rand($this->fonts)];
-            $flyweight = $factory->$char;
-            // External state can be passed in like this:
-            // $flyweight->draw($font);
+        foreach ($this->characters as $char) {
+            foreach ($this->fonts as $font) {
+                $flyweight = $factory->get($char);
+                $rendered = $flyweight->render($font);
+
+                $this->assertEquals(sprintf('Character %s with font %s', $char, $font), $rendered);
+            }
         }
 
         // Flyweight pattern ensures that instances are shared
         // instead of having hundreds of thousands of individual objects
-        $this->assertLessThanOrEqual($factory->totalNumber(), count($this->characters));
+        // there must be one instance for every char that has been reused for displaying in different fonts
+        $this->assertCount(count($this->characters), $factory);
     }
 }

Structural/Flyweight/uml/Flyweight.uml

@@ -1,25 +1,24 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Diagram>
   <ID>PHP</ID>
-  <OriginalElement>\DesignPatterns\Structural\Flyweight\FlyweightFactory</OriginalElement>
+  <OriginalElement>\DesignPatterns\Structural\Flyweight\CharacterFlyweight</OriginalElement>
   <nodes>
-    <node x="14.0" y="109.0">\DesignPatterns\Structural\Flyweight\CharacterFlyweight</node>
-    <node x="235.0" y="0.0">\DesignPatterns\Structural\Flyweight\FlyweightFactory</node>
-    <node x="-8.0" y="0.0">\DesignPatterns\Structural\Flyweight\FlyweightInterface</node>
+    <node x="19.0" y="101.0">\DesignPatterns\Structural\Flyweight\CharacterFlyweight</node>
+    <node x="230.0" y="94.0">\DesignPatterns\Structural\Flyweight\FlyweightFactory</node>
+    <node x="0.0" y="0.0">\DesignPatterns\Structural\Flyweight\FlyweightInterface</node>
   </nodes>
   <notes />
   <edges>
     <edge source="\DesignPatterns\Structural\Flyweight\CharacterFlyweight" target="\DesignPatterns\Structural\Flyweight\FlyweightInterface">
-      <point x="0.0" y="-56.5" />
-      <point x="0.0" y="29.5" />
+      <point x="0.0" y="-37.0" />
+      <point x="0.0" y="25.5" />
     </edge>
   </edges>
-  <settings layout="Hierarchic Group" zoom="1.0" x="191.0" y="111.0" />
+  <settings layout="Hierarchic Group" zoom="1.0" x="76.0" y="91.0" />
   <SelectedNodes />
   <Categories>
     <Category>Fields</Category>
     <Category>Constants</Category>
-    <Category>Constructors</Category>
     <Category>Methods</Category>
   </Categories>
   <VISIBILITY>private</VISIBILITY>