NestJS NestJS Architecture & Design Patterns 2

Question 1

Which decorator transforms a plain class into a NestJS injectable service?

Accepted Answer

@Injectable()

Answer

@Injectable() marks a class as a provider that the NestJS IoC container can instantiate and inject into other classes.

Question 2

What is a Dynamic Module in NestJS?

Accepted Answer

A module that exports configuration-based providers at import time

Answer

A Dynamic Module returns a module configuration object (including providers) at import time, enabling customizable, reusable modules like ConfigModule.forRoot().

Question 3

Which SOLID principle is most directly enforced by NestJS's dependency injection system?

Accepted Answer

Dependency Inversion

Answer

NestJS DI enforces the Dependency Inversion Principle by having high-level modules depend on abstractions (tokens/interfaces) rather than concrete implementations.

Question 4

How do you create a circular dependency between two NestJS providers without causing errors?

Accepted Answer

Use forwardRef() in both @Inject() decorators

Answer

forwardRef() wraps the class reference to defer its resolution, allowing NestJS to break the circular dependency loop during instantiation.

Question 5

What does the `imports` array in @Module() accept?

Accepted Answer

Other module classes whose exported providers are needed

Answer

The `imports` array takes other NestJS module classes, making their exported providers available for injection within the importing module.

NestJS Practice Test

NestJS Practice Test

NestJS NestJS Architecture & Design Patterns 2