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decorators

@webda/decorators​

Utility factories for authoring TC39-standard decorators that work both with and without parentheses — the dual-mode pattern used throughout the Webda framework.

When to use it​

Use @webda/decorators whenever you want to write your own custom TypeScript decorators without boilerplate dispatch logic. It handles the "called directly vs called as factory" ambiguity for you, for class, method, and field (property) decorators.

Note: Ready-made Webda decorators like @Bean, @Inject, @Route, @Operation, and @Expose ship with @webda/core and @webda/models. This package provides the factories to build new ones.

Install​

npm install @webda/decorators

Usage​

import {
  createClassDecorator,
  createMethodDecorator,
  createPropertyDecorator,
  getMetadata
} from "@webda/decorators";

// Class decorator — with or without options
const Singleton = createClassDecorator(
  (cls, context, options?: { eager: boolean }) => {
    context.metadata["singleton"] = options ?? { eager: false };
  }
);

@Singleton                   // direct — no arguments
class ServiceA {}

@Singleton({ eager: true })  // factory — with arguments
class ServiceB {}

// Method decorator
const Log = createMethodDecorator(
  (method, context, prefix?: string) => {
    return function (this: any, ...args: any[]) {
      console.log(`[${prefix ?? String(context.name)}]`, ...args);
      return method.apply(this, args);
    };
  }
);

class Api {
  @Log           getUser() {}
  @Log("fetch")  getOrder() {}
}

// Field decorator
const Expose = createPropertyDecorator(
  (context: ClassFieldDecoratorContext, alias?: string) => {
    context.metadata["expose"] ??= [];
    (context.metadata["expose"] as string[]).push(alias ?? String(context.name));
  }
);

class User {
  @Expose           name: string;
  @Expose("usr_id") id: string;
}

// Read metadata from a class
const meta = getMetadata(User);
console.log(meta["expose"]); // ["name", "usr_id"]

API reference​

ExportKindDescription
createClassDecorator(impl)FactoryCreates a dual-mode class decorator
createMethodDecorator(impl)FactoryCreates a dual-mode method decorator
createPropertyDecorator(impl)FactoryCreates a dual-mode field decorator
getMetadata(Class)HelperReturns Class[Symbol.metadata]
AnyCtorTypeabstract new (...args) => T
AnyMethodType(...args) => any
ClassDecoratorTypeReturn type of createClassDecorator
MethodDecoratorTypeReturn type of createMethodDecorator
FieldDecoratorTypeReturn type of createPropertyDecorator
DecoratorPropertyParameters<T>Type utilityExtracts extra arg types from a property decorator

See also​

Type Aliases​

Functions​