Questions
2 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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02 / 07

How do you create a custom parameter decorator in NestJS?

Use createParamDecorator which receives a factory function with (data, ctx) arguments. The data argument is whatever is passed into the decorator at usage time, and ctx is the ExecutionContext providing access to the request, response, and other context.

Custom @CurrentUser() decorator
Key points:
  1. 1

    createParamDecorator takes a factory function that receives data and ctx.

  2. 2

    data is the argument passed to the decorator at the call site.

  3. 3

    ctx.switchToHttp().getRequest() gives the underlying HTTP request.

  4. 4

    Custom param decorators can be combined with pipes for validation.