In Nest Js How To Get A Service Instance Inside A Decorator

Are you delving into Nest.js and wondering how to get a service instance inside a decorator? Well, fret not, because I've got you covered with a quick and easy guide to help you navigate this process smoothly.

When working with Nest.js, decorators play a crucial role in adding metadata or functionality to your classes or class members. However, it can be a bit tricky at first to access a service instance inside a decorator. But fear not, as I'll walk you through the steps to accomplish this seamlessly.

To get a service instance inside a decorator in Nest.js, you'll need to make use of the `Reflector` class provided by the `@nestjs/core` package. The `Reflector` class allows you to retrieve metadata stored on a given class, method, or property.

Here's a step-by-step guide to help you achieve this:

1. Import the `Reflector` class:
You need to import the `Reflector` class from `@nestjs/core` in your decorator file. Make sure to install the `@nestjs/core` package if you haven't already.

Typescript

import { Reflector } from "@nestjs/core";

2. Inject the `Reflector` class:
Next, you should inject the `Reflector` class into your decorator class. You can do this by adding it to the constructor parameters.

Typescript

import { Injectable, Inject } from "@nestjs/common";
    
   @Injectable()
   export class MyDecorator {
     constructor(@Inject(Reflector) private readonly reflector: Reflector) {}
   }

3. Retrieve the service instance:
Once you have the `Reflector` class injected, you can use it to retrieve the service instance. You can do this within the decorator method by accessing the metadata stored on the class.

Typescript

export function MyDecorator(): (target, key, descriptor) =&gt; {
     return (target, key, descriptor) =&gt; {
       const serviceInstance = this.reflector.get('service', target.constructor);
       
       // Now you have access to the service instance!
     };
   };

4. Usage example:
Finally, you can apply your decorator to the desired class or method and access the service instance inside the decorator.

Typescript

@MyDecorator()
   export class MyService {
     constructor(private readonly myOtherService: MyOtherService) {}
   }

And there you have it! By following these steps, you can easily access a service instance inside a decorator in Nest.js. Decorators are a powerful tool in Nest.js for extending and modifying classes, and with this knowledge, you can leverage them effectively in your projects. Happy coding!

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