oliverdavies.uk/content/node.166d5baa-74b2-498c-b2cf-a15ddf4df6a0.yml

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title:
  - value: |
      The Decorator design pattern
created:
  - value: '2022-12-08T00:00:00+00:00'
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      <p>Decorator is a structural design pattern that allows you to add extra functionality, such as if you want to add caching or logging to a service, without changing the original class.</p>

      <p>As long as a class implements an Interface, it can be decorated.</p>

      <p>For example, if I have this PHP interface:</p>

      <pre><code class="language-php">interface DoesSomething
      {
          public function doSomething(): void;
      }
      </code></pre>

      <p>I could have this class that does something:</p>

      <pre><code class="language-php">final class FirstClass implements DoesSomething
      {
          public function doSomething(): void
          {
              // Does something.
          }
      }
      </code></pre>

      <p>If I need to do something else, like caching or logging the result, I can decorate it.</p>

      <p>To do this, I need another class that implements the same interface and inject the original version.</p>

      <pre><code class="language-php">final class SecondClass implements DoesSomething
      {
          public function __constuct(
              private DoesSomething $originalClass
         ) {}

          public function doSomething()
          {
              // Do something else before.

              $this-&gt;originalClass-&gt;doSomething();

              // Do something else afterwards.
          }
      }
      </code></pre>

      <p>Within the new class, the methods can be overridden, extra functionality can be added, and the original method can be run to execute the original functionality.</p>

      <p>As the two classes implement the same interface, I can swap between different versions and decorate multiple times if needed.</p>

      <p>This a pattern that I used recently to extend a service that retrieved some data from an API and saved it to a file, to change some arguments and do more work with it.</p>

      <p>The original class was unchanged, the new class was minimal and easy to understand as it only had a single responsibility, and if I needed to switch back to the original version, I could easily do that.</p>

              
    format: full_html
    processed: |
      <p>Decorator is a structural design pattern that allows you to add extra functionality, such as if you want to add caching or logging to a service, without changing the original class.</p>

      <p>As long as a class implements an Interface, it can be decorated.</p>

      <p>For example, if I have this PHP interface:</p>

      <pre><code class="language-php">interface DoesSomething
      {
          public function doSomething(): void;
      }
      </code></pre>

      <p>I could have this class that does something:</p>

      <pre><code class="language-php">final class FirstClass implements DoesSomething
      {
          public function doSomething(): void
          {
              // Does something.
          }
      }
      </code></pre>

      <p>If I need to do something else, like caching or logging the result, I can decorate it.</p>

      <p>To do this, I need another class that implements the same interface and inject the original version.</p>

      <pre><code class="language-php">final class SecondClass implements DoesSomething
      {
          public function __constuct(
              private DoesSomething $originalClass
         ) {}

          public function doSomething()
          {
              // Do something else before.

              $this-&gt;originalClass-&gt;doSomething();

              // Do something else afterwards.
          }
      }
      </code></pre>

      <p>Within the new class, the methods can be overridden, extra functionality can be added, and the original method can be run to execute the original functionality.</p>

      <p>As the two classes implement the same interface, I can swap between different versions and decorate multiple times if needed.</p>

      <p>This a pattern that I used recently to extend a service that retrieved some data from an API and saved it to a file, to change some arguments and do more work with it.</p>

      <p>The original class was unchanged, the new class was minimal and easy to understand as it only had a single responsibility, and if I needed to switch back to the original version, I could easily do that.</p>

              
    summary: null
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