<aside> ➡️ The pages under the Engineering page are currently curated by the company's chief technical officer (CTO). To contribute, please leave a comment. How to comment?

</aside>

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When developing a Magento2 app, you may need to change a function in a core class to work in a particular way that is not implemented by default, so it serves your app some purposes.

When you use block, model, controller, helper in Magento 2, it's a bad practice to modify code pulled in a version-controlled package by hand, for some obvious reasons:

1. Modifying core files may have a certain influence on another program or module.
2. Your modifications will be wiped out when you update the framework, those classes you modified will be replaced with new core files.
3. Code in vendor is not (and should not be) controlled, so nobody will get the changes you make.

The solution to this problem is to override the files, but...

How to Modify files without touching the source code?

When you have to modify a core class in Magento2, you have two possibilities:

• **Plugin -** with which you can execute some code before, after, and around the code/target class’s function.
• **Preference -** with which you can extend a core class to rewrite the functions of that class and the new class is expected to be a complete implementation of the extended class.

<aside> ➡️ There are other ways of affecting functionality, such as changing di.xml parameters, Event listeners, but it has its use cases.

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In this guide, we're taking a look at plugins.

What is a plugin?

Magento 2 Plugin is referred to as a class extension that allows modifying the behavior of a public class or method by intercepting a function call and running code either before or after or around the function call. The plugin allows you to substitute or extend the behavior of original, public methods for any class or interface.

Why and when should I use plugins?

If you need to:

• modify the return value of any method call
• forward any method call
• modify arguments of any method call

<aside> ➡️ Plugins can not be used on the __construct method of a class.

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What type of plugin should I use?

There are three types of plugins namely:

• Before - it changes the arguments provided to a method or executes something before the method itself is executed.
• After - to "rework" the output of a method or execute something based on the method result, aka. after the method is executed.
• Around - modifies the behavior of a method, allows you to execute something before, after, or around the method. You might even not call the original method at all!

How to create a plugin?

We will be creating a plugin for the below class example: