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