Nest can't resolve dependencies of the UsersService (UserModel, ?)

Question

my user.module.ts:

import { forwardRef, Module } from '@nestjs/common';
import { UsersService } from './users.service';
import { UsersController } from './users.controller';
import { UserSchema } from './schemas/user.schema';
import { MongooseModule } from '@nestjs/mongoose';
import { AuthModule } from 'src/auth/auth.module';


@Module({
  imports: [MongooseModule.forFeature([{name: 'User', schema: UserSchema}]),AuthModule],
  controllers: [UsersController],
  providers: [UsersService],
  exports: [UsersService]
})
export class UsersModule {}

my auth.module.ts

import { forwardRef, Module } from '@nestjs/common';
import { AuthService } from './auth.service';
import { UsersModule } from '../users/users.module';
import { PassportModule } from '@nestjs/passport';
import { LocalStrategy } from './local.strategy';

@Module({
  imports: [forwardRef(() => UsersModule), PassportModule],
  providers: [AuthService, LocalStrategy],
})
export class AuthModule {}

my app.module.ts

import { Module } from '@nestjs/common';
import { MongooseModule } from '@nestjs/mongoose';
import { AppController } from './app.controller';
import { AppService } from './app.service';
import { UsersModule } from './users/users.module';


@Module({
  imports: [UsersModule,MongooseModule.forRoot('mongodb://localhost:27017/nest1')],
  controllers: [AppController],
  providers: [AppService],
})
export class AppModule {}

this are giving me error:

[12:55:42 pm] Found 0 errors. Watching for file changes.

[Nest] 15944 - 20/09/2021, 12:55:45 pm LOG [NestFactory] Starting Nest application... [Nest] 15944 - 20/09/2021, 12:55:45 pm LOG [InstanceLoader] MongooseModule dependencies initialized +126ms [Nest] 15944 - 20/09/2021, 12:55:46 pm ERROR [ExceptionHandler] Nest can't resolve dependencies of the UsersService (UserModel, ?). Please make sure that the argument AuthService at index [1] is available in the UsersModule context.

Potential solutions:

• If AuthService is a provider, is it part of the current UsersModule?
• If AuthService is exported from a separate @Module, is that module imported within UsersModule? @Module({ imports: [ /* the Module containing AuthService */ ] })

Error: Nest can't resolve dependencies of the UsersService (UserModel, ?). Please make sure that the argument AuthService at index [1] is available in the UsersModule context.

Potential solutions:

• If AuthService is a provider, is it part of the current UsersModule?

• If AuthService is exported from a separate @Module, is that module imported within UsersModule? @Module({ imports: [ /* the Module containing AuthService */ ] })

  at Injector.lookupComponentInParentModules (C:\Users\Asus\Desktop\BILDEMP\ems-by-nestjs\employee-management-system\node_modules@nestjs\core\injector\injector.js:193:19) at Injector.resolveComponentInstance (C:\Users\Asus\Desktop\BILDEMP\ems-by-nestjs\employee-management-system\node_modules@nestjs\core\injector\injector.js:149:33) at resolveParam (C:\Users\Asus\Desktop\BILDEMP\ems-by-nestjs\employee-management-system\node_modules@nestjs\core\injector\injector.js:103:38) at async Promise.all (index 1) at Injector.resolveConstructorParams (C:\Users\Asus\Desktop\BILDEMP\ems-by-nestjs\employee-management-system\node_modules@nestjs\core\injector\injector.js:118:27) at Injector.loadInstance (C:\Users\Asus\Desktop\BILDEMP\ems-by-nestjs\employee-management-system\node_modules@nestjs\core\injector\injector.js:47:9) at Injector.loadProvider (C:\Users\Asus\Desktop\BILDEMP\ems-by-nestjs\employee-management-system\node_modules@nestjs\core\injector\injector.js:69:9) at async Promise.all (index 3) at InstanceLoader.createInstancesOfProviders (C:\Users\Asus\Desktop\BILDEMP\ems-by-nestjs\employee-management-system\node_modules@nestjs\core\injector\instance-loader.js:44:9) at C:\Users\Asus\Desktop\BILDEMP\ems-by-nestjs\employee-management-system\node_modules@nestjs\core\injector\instance-loader.js:29:13

Answer 1

I'm going to make some assumptions about your service constructors, as you haven't provided those:

You have what looks to be a circular reference between the UserModule and the AuthModule. Because of this, in the imports of each module you need to use forwardRef of the module you're importing.

@Module({
  imports: [forwardRef(() => UserModule), ...rest],
  providers,
  controllers,
  exports
})
export class AuthModule {}

@Module({
  imports: [forwardRef(() => AuthModule), ...rest],
  providers,
  controllers,
  exports
})
export class UserModule {}

And speaking of exports above, you need to export a provider if you plan to use it outside of the module where it is in the providers (e.g. to use AuthService inside of UserService, the AuthModule needs to have providers: [AuthService] and exports: [AuthService]. This makes the provider available elsewhere.

Now, to make use of circular dependencies inside of the services, you also need to make use of forwardRef. In this case it will look like @Inject(forwardRef(() => OtherClass)) private readonly other: OtherClass, so you'd have something like

@Injectable()
export class UserService {
  constructor(
    @Inject(forwardRef(() => AuthService)) private readonly auth: AuthService,
    private readonly dep2: DependencyClass2
  ) {}

  // rest of values
}

You'll do the same thing in the AuthService but replacing AuthService in the @Inject() with UserService.

Answer 2

You have to export the auth service in the authmodule in order to be able to inject it in the user service.

Answer 3

You need to import all the dependencies of UserService in UserModule. If you still can't figure out then please also add your user.service.ts file in the question.