What is the purpose of a module in NestJS and what does the @Module() decorator do?

Difficulty: 4/10

Modules, Dependency Injection, Application Structure

A module is the primary organizational unit in NestJS. The @Module() decorator provides metadata that NestJS uses to build the application graph and resolve the DI container. Every app needs at least one root module — AppModule. Modules encapsulate a cohesive slice of functionality: controllers, providers, and their import/export relationships.

Modules group related controllers and providers together into a cohesive unit. NestJS reads the @Module() metadata at bootstrap to build the dependency graph and wire up the IoC container. Providers not listed in exports are private to the module and invisible outside it.

Basic module structure

The four @Module() properties:

1
imports — other modules whose exported providers this module needs.
2
controllers — controllers that handle incoming requests for this module.
3
providers — services, guards, pipes, and other injectables scoped to this module.
4
exports — providers or re-exported modules made available to any module that imports this one.

Scenario Questions

0-2 years experience

Follow-up Questions