How to create custom decorator in loopback4?

Question

  async checkUserMemberOfProduct(userId: string, productId: string) {
    if (userId && productId) {
       const user = await Product.find({ where: { userId: userId, id: productId } });
       return !!user;
    }
    return false;
  }

I want to create this function as decorator. And call it above endpoint. For example

  @checkUserMemberOfProduct()

  @post('/roles')
  async create(
    @requestBody() user: User
  ): Promise<Role> {
    return this.roleRepository.create(role);
  }

But I am not sure how to pass request body to this decorator. Is it possible to use this fn as decorator?

Answer 1

I think an interceptor may work. Heres an example code.

import {inject, intercept, Interceptor} from '@loopback/context';
import {get, HttpErrors, RestBindings} from '@loopback/rest';

const myInterceptor: Interceptor = async (invocationCtx, next) => {
  // your code 
  // goes here

  // if success
  next()

  // if error
  throw new HttpErrors.NotFound();
};

export class PingController {
  constructor() {}

  @intercept(myInterceptor)
  @post('/test')
  async test(@requestBody() body: any) {
    // some code
  }
}