Modules & Sharing

Preview — 3 of 10 questions

A UsersModule declares UsersService in providers but does not list it in exports. Another module imports UsersModule and tries to inject UsersService. What happens?

javascript

@Module({
  providers: [UsersService],
  exports: [UsersService], // ← required for other modules to inject it
})
export class UsersModule {}

AIt silently injects undefined

BIt works, because importing a module exposes all of its providers

CNest throws an "Nest can't resolve dependencies" error because the provider was never exported

DIt works only if UsersService is @Global()

Why is a SharedModule commonly used in larger Nest applications?

javascript

@Module({
  providers: [LoggerService],
  exports: [LoggerService],
})
export class SharedModule {}

ATo group commonly-used providers and re-export them so multiple feature modules can import one module instead of many

BTo make all providers globally available without importing anything

CTo bypass dependency injection entirely for shared state

DTo store environment variables centrally

Two modules depend on each other's exports. How do you resolve the circular module dependency?

javascript

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

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

AMerge them into one giant module — circular deps are forbidden

BUse @Global() on both modules

CWrap each module reference in forwardRef(() => OtherModule) inside both imports arrays

DAdd circular: true to the @Module metadata

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