Inject NestJS Service from Another Module

In NestJS, services are an essential part of the application, and they can be injected and used across different modules. To inject a NestJS service from another module, you need to ensure that the service is exported and that the module where it is provided is imported into the module where you want to use the service.

Creating the Service

First, you need to create the service that you want to inject. For example, let's create a simple service called ExampleService.

// example.service.ts

import { Injectable } from '@nestjs/common';

@Injectable()
export class ExampleService {
  getHello(): string {
    return 'Hello from ExampleService!';
  }
}

Providing the Service

Next, you need to provide the service within a module. This is typically done in the module's providers array. Let's assume the service is provided in the ExampleModule.

// example.module.ts

import { Module } from '@nestjs/common';
import { ExampleService } from './example.service';

@Module({
  providers: [ExampleService],
  exports: [ExampleService],
})
export class ExampleModule {}

In this example, we import the ExampleService and add it to the providers array. We also use the exports array to make the service available for injection in other modules.

Importing the Module with the Service

To inject the ExampleService from another module, you need to import the ExampleModule that provides the service. Let's assume we want to use the ExampleService in the AppModule.

// app.module.ts

import { Module } from '@nestjs/common';
import { ExampleModule } from './example/example.module';
import { AppController } from './app.controller';
import { AppService } from './app.service';

@Module({
  imports: [ExampleModule], // Import the ExampleModule here
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

Injecting the Service

Now that the ExampleService is provided and exported from the ExampleModule, you can inject it into any constructor in the AppModule or any other module that imports ExampleModule.

// app.service.ts

import { Injectable } from '@nestjs/common';
import { ExampleService } from './example/example.service';

@Injectable()
export class AppService {
  constructor(private readonly exampleService: ExampleService) {}

  getHello(): string {
    return this.exampleService.getHello();
  }
}

In this example, we import the ExampleService from the ExampleModule and inject it into the AppService constructor. Now, we can use the methods provided by the ExampleService within the AppService.