Param

Kind: Function

Source: packages/common/decorators/http/route-params.decorator.ts

Part of: Common

Route handler parameter decorator. Extracts the params property from the req object and populates the decorated parameter with the value of params. May also apply pipes to the bound parameter.

For example, extracting all params:

typescript
findOne(@Param() params: string[])

For example, extracting a single param:

typescript
findOne(@Param('id') id: string)

Param() binds route parameters from req.params to a controller handler argument. Pass a parameter name to extract one value, or omit it to receive the full params object; pipes can transform or validate the bound value.

Signature

ts
function Param(property: string | (Type<PipeTransform> | PipeTransform), pipes: (Type<PipeTransform> | PipeTransform)[]): ParameterDecorator

Parameters

Returns: ParameterDecorator

Diagram

mermaid
graph LR
  Request[HTTP request] --> ReqParams[req.params]
  ReqParams --> ParamDecorator["@Param()"]
  ParamDecorator --> HandlerParameter[Route handler parameter]
  Pipes[Pipes, if provided] --> HandlerParameter

Usage

typescript
import { Controller, Get, Param } from '@nestjs/common';

@Controller('users')
export class UsersController {
  @Get(':id')
  findOne(@Param('id') id: string) {
    return { id };
  }

  @Get(':userId/posts/:postId')
  findPost(@Param() params: Record<string, string>) {
    return params;
  }
}

AI Coding Instructions

• Use @Param('name') when a handler needs one named route parameter.
• Use @Param() without a name when the handler needs the complete req.params object.
• Keep the decorator parameter name aligned with the route token, such as @Get(':id') and @Param('id').
• Attach pipes to @Param() when route parameter values require validation or transformation before reaching the handler.