How to Inject plain Service/Provider in nest.js

Question

I made a plain typeScript class in nest.js. JwtTokenService.js

// JwtTokenService.js

import { Injectable, Optional } from '@nestjs/common';
import { JwtService } from '@nestjs/jwt';
import { JwtPayload } from '../modules/auth/interface/jwt-payload.interface';

@Injectable()
export class JwtTokenService {
  constructor(private readonly jwtService: JwtService) {}

  async generateJWT(payload: object): Promise<string> {
    payload['type'] = 'access_token';
    const token = this.jwtService.sign({ payload });
    return token;
  }
}

Now how can I use this in any controller. like user, auth and other.

Answer 1

Register the service in the nest application module:

import { Module } from '@nestjs/common';
import { YourController } from './path-to/your.controller';
import { JwtTokenService } from './path-to/JwtTokenService.service';

@Module({
  controllers: [YourController],
  providers: [JwtTokenService],
})
export class ApplicationModule {}

Then you can use it in your controller:

import { Controller, Get, Post, Body } from '@nestjs/common';
import { JwtTokenService } from './path-to/JwtTokenService.service';

@Controller('your')
export class YourController {
  constructor(private readonly jwtTokenService: JwtTokenService) {}

  @Get()
  async get() {
    // use `this.jwtTokenService`
    ...
  }
}

Nest is using the a DependencyInjection pattern to provide the service to the controller, which is why you need to declare how the service is provided in the application module.