Questions
7 of 7
1What is a decorator in TypeScript and how does NestJS use decorators?
2How do you create a custom parameter decorator in NestJS?
3What is Reflector and how does it work with SetMetadata in NestJS?
4What are the different types of decorators and their execution order in TypeScript?
5How do you use a custom param decorator together with a pipe for automatic validation in NestJS?
6How do you create a custom parameter decorator in NestJS?
7How do you compose multiple decorators into a single reusable decorator in NestJS?
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How do you compose multiple decorators into a single reusable decorator in NestJS?

Use applyDecorators() to bundle multiple decorators — including guards, metadata decorators, and Swagger decorators — into one named decorator. This reduces boilerplate on routes and co-locates all related concerns under a single, intention-revealing name like @Auth() or @ApiPaginatedResponse().

@Auth() composite decorator using applyDecorators
applyDecorators() design guidance:
  1. 1

    Accepts any combination of method and class decorators.

  2. 2

    Decorators are applied in the order listed — first in the array runs first.

  3. 3

    Works for both method-level and class-level composition.

  4. 4

    Ideal for bundling auth + Swagger + metadata decorators that always go together.

  5. 5

    The composed decorator has a meaningful name — @Auth('admin') communicates intent better than 4 separate decorators.