docs(daily-email): add 2022-12-08

website/src/daily-emails/2022-12-08.md

@@ -0,0 +1,64 @@
+---
+title: >
+  The Decorator design pattern
+pubDate: 2022-12-08
+permalink: >
+  archive/2022/12/08/the-decorator-design-pattern
+tags:
+  - design-patterns
+---
+
+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.
+
+As long as a class implements an Interface, it can be decorated.
+
+For example, if I have this PHP interface:
+
+```php
+interface DoesSomething
+{
+    public function doSomething(): void;
+}
+```
+
+I could have this class that does something:
+
+```php
+final class FirstClass implements DoesSomething
+{
+    public function doSomething(): void
+    {
+        // Does something.
+    }
+}
+```
+
+If I need to do something else, like caching or logging the result, I can decorate it.
+
+To do this, I need another class that implements the same interface and inject the original version.
+
+```php
+final class SecondClass implements DoesSomething
+{
+    public function __constuct(
+        private DoesSomething $originalClass
+   ) {}
+
+    public function doSomething()
+    {
+        // Do something else before.
+
+        $this->originalClass->doSomething();
+
+        // Do something else afterwards.
+    }
+}
+```
+
+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.
+
+As the two classes implement the same interface, I can swap between different versions and decorate multiple times if needed.
+
+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.
+
+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.