HostParam

Kind: Function

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

Part of: Common

Route handler parameter decorator. Extracts the hosts 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(@HostParam() params: string[])

For example, extracting a single param:

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

HostParam() binds a route handler parameter to values extracted from the request host and stored on req.hosts. Pass a host parameter name to read one value, or omit the name to receive the full host parameter object; pipes can transform or validate the bound value.

Signature

ts
function HostParam(property: string | (Type<PipeTransform> | PipeTransform)): ParameterDecorator

Parameters

Returns: ParameterDecorator

Diagram

mermaid
graph LR
  Request[Incoming request host] --> Matcher[Host route matcher]
  Matcher --> Hosts[req.hosts]
  Hosts --> Decorator["@HostParam()"]
  Decorator --> Handler[Route handler parameter]
  Decorator --> Pipes[Pipes]
  Pipes --> Handler

Usage

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

@Controller({ host: ':account.example.com' })
export class AccountController {
  @Get()
  findAccount(@HostParam('account') account: string) {
    return { account };
  }

  @Get('host-params')
  findHostParams(@HostParam() params: Record<string, string>) {
    return params;
  }
}

AI Coding Instructions

• Use @HostParam('name') when the controller host pattern defines a named parameter such as :account.
• Use @HostParam() when the handler needs every value from req.hosts.
• Keep host parameter names aligned with the names declared in the controller host pattern.
• Add pipes as additional decorator arguments when the bound host value needs validation or transformation.