CreateDecoratorOptions

Kind: Interface

Source: packages/core/services/reflector.service.ts

Part of: Core

CreateDecoratorOptions configures how a reflector decorator reads and transforms metadata values. It defines the metadata key to access and a transform function that converts the raw parameter value into the type consumed by the decorator or reflector service.

Properties

Diagram

mermaid
graph LR
  A[Decorator Invocation] --> B[CreateDecoratorOptions]
  B --> C[key: string]
  B --> D[transform(value)]
  C --> E[Reflector Metadata Lookup]
  E --> F[Raw Metadata Value]
  F --> D
  D --> G[Transformed Metadata Value]

Usage

ts
import type { CreateDecoratorOptions } from '@nestjs/core/services/reflector.service';

interface RoleOptions {
  roles: string[];
}

const roleDecoratorOptions: CreateDecoratorOptions<
  string[],
  RoleOptions
> = {
  key: 'roles',
  transform: (roles) => ({
    roles: roles.map((role) => role.toLowerCase()),
  }),
};

// The transform function receives the raw metadata value and returns
// the normalized value used by the application.
const normalizedRoles = roleDecoratorOptions.transform(['ADMIN', 'EDITOR']);

// { roles: ['admin', 'editor'] }
console.log(normalizedRoles);

AI Coding Instructions

• Use a stable, unique key string that matches the metadata key used by the associated decorator.
• Keep transform pure: it should convert the input value without mutating it or relying on external state.
• Type TParam to match the raw decorator input and TTransformed to match the value consumers should receive.
• Validate or normalize optional, array, and nested values inside transform when downstream code expects a consistent shape.
• Ensure metadata readers use the same key and expect the transformed output type rather than the raw decorator argument.

Relationships

• IMPORTS → CustomDecorator
• IMPORTS → SetMetadata
• IMPORTS → Type
• IMPORTS → isEmpty
• IMPORTS → isObject