Shared modules in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a shared module in NestJS?

A shared module is a module that exports providers, components, or services so other modules can use them without redefining. It helps reuse code across the app.

beginner

How do you make a module shared in NestJS?

You export the providers or components inside the module's @Module decorator using the 'exports' array. Then import this module in other modules to use the shared parts.

intermediate

Does importing a shared module multiple times create multiple instances of its providers in NestJS?

No, NestJS automatically shares a single instance of providers across all modules that import it.

beginner

What is the difference between 'imports' and 'exports' in a NestJS module?

'imports' bring in other modules to use their exported providers. 'exports' make providers from the current module available to other modules that import it.

intermediate

Can a shared module import other modules? What happens then?

Yes, a shared module can import other modules. Those imported modules' exported providers become available inside the shared module, but are not automatically exported to modules importing the shared module.

What must you do to make a service available to other modules in NestJS?

A Add the service to the module's exports array

B Add the service to the module's imports array

C Declare the service in the main.ts file

D Use the service without importing the module

You export the service in the module's exports array so other modules importing this module can use it.

If you import a shared module in multiple modules, what happens to its providers?

A They are duplicated for each import

B They are removed from the app

C They are shared as single instances

D They cause an error

Providers in a shared module are singletons and shared across imports unless explicitly scoped differently.

Which decorator property lists modules that this module depends on?

A exports

B imports

C providers

D controllers

'imports' lists modules whose exported providers are needed inside this module.

What is the main benefit of using shared modules?

A To reduce code duplication and reuse services

B To increase app size

C To create multiple instances of services

D To avoid using providers

Shared modules help reuse code and services across different parts of the app, reducing duplication.

If a shared module imports another module, do the imported module's exports become available to modules importing the shared module?

A Yes, automatically

B No, only inside the shared module

C Only if the imported module is global

D Only if the shared module re-exports them

The shared module must re-export the imported module's exports to make them available to modules importing the shared module.

Explain how to create and use a shared module in NestJS.

Think about how to share services across modules without rewriting them.

Describe the difference between 'imports' and 'exports' in a NestJS module and why both are important.

Consider how modules connect and share code.