Global modules in NestJS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a global module in NestJS?

A global module is a module that is automatically available across the entire application without needing to import it in other modules.

beginner

How do you make a module global in NestJS?

You add the @Global() decorator above the module class and then export the providers you want to share.

intermediate

Why use global modules in NestJS?

Global modules help avoid repetitive imports of common services or providers in many modules, making code cleaner and easier to maintain.

intermediate

Can you import a global module multiple times in NestJS?

No, once a module is marked global, you do not need to import it in other modules. Importing it again has no effect.

beginner

Show a simple example of a global module in NestJS.

```typescript
import { Module, Global } from '@nestjs/common';

@Global()
@Module({
  providers: [CommonService],
  exports: [CommonService],
})
export class CommonModule {}
```

What decorator makes a module global in NestJS?

A @Module()

B @Global()

C @Injectable()

D @Controller()

The @Global() decorator marks a module as global so it can be used without importing it everywhere.

If a module is global, do you need to import it in every other module?

A Yes, always

B Only in controllers

C No, it is available automatically

D Only if it has providers

Global modules are automatically available in all modules without importing.

What must you do to share a service from a global module?

A Export the service in the module exports array

B Import the service in every module

C Use @Injectable() only

D Nothing, it is shared by default

You must export the service in the module's exports array to share it.

Which of these is NOT a benefit of global modules?

A Cleaner module code

B Make services available app-wide

C Avoid repetitive imports

D Automatically reload modules on change

Global modules do not affect module reloading behavior.

Where do you place the @Global() decorator?

A Above the module class

B Above the service class

C Inside the module imports array

D Inside the main.ts file

The @Global() decorator is placed above the module class declaration.

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

Think about how to share services app-wide without importing everywhere.

What are the advantages and possible downsides of using global modules in NestJS?

Consider both code simplicity and clarity.