TypeORM AfterSave() triggers after creation but when queried, it returns NULL

I have an Entity called Trip. The structure is:

What I want is whenever a new trip is created, the room column should be populated with ${tripId}_${someRandomStringHere}. So for example, I just created a new trip using this body:

The response should be:

The newly created trip has the id of 15. So, the response has the room valued at 15_4gupvdo0ea408c25ia0qsbh because again: ${tripId}_${someRandomStringHere}.

This is working as expected whenever I POST the request and create the trip. BUT whenever I query all the trips created, the room property of each trip objects shows null!

Look at the /api/trips:

room property is NULL. So what the heck I dont understand what is happening.

My Trip Entity code is:

import { PrimaryGeneratedColumn, Column, CreateDateColumn, 
UpdateDateColumn, Entity, Unique, ManyToOne, AfterInsert, JoinColumn, getConnection } from 'typeorm'
import { DriverEntity } from 'src/driver/driver.entity';

@Entity('trips')
export class TripEntity {
  @PrimaryGeneratedColumn()
  id: number

  @Column()
  destination: string

  @Column('decimal')
  destination_lat: number

  @Column('decimal')
  destination_long: number

  @Column()
  maxPassenger: number

  @Column()
  totalPassenger: number

  @Column({ nullable: true })
  room: string

  @CreateDateColumn()
  created_at: Date

  @UpdateDateColumn()
  updated_at: Date
// --------->HERE: The after insert 
  @AfterInsert()
  async createSocketRoom(): Promise<void> {
    const randomString = Math.random().toString(36).substring(2, 15) + Math.random().toString(36).substring(2, 15)
    this.room =  `${this.id}_${randomString}`
  }

  // Trip belongs to driver
  // Adds driver_id to trips table
  @ManyToOne(type => DriverEntity, driver => driver.trips)
  @JoinColumn({ name: 'driver_id' })
  driver: DriverEntity
}

My Trip Service Code is:

async create(data: CreateTripDTO) {
    const { driver_id } = data
    const driver = await this.driverRepository.findOne({ where: { id: driver_id } })
    const trip = await this.tripRepository.create(data)
    trip.driver = driver

    await this.tripRepository.save(trip)
    return trip
  }

I dont think I need to include the Trip Controller code but anyway.. I don't know why it is happening because I have my User Entity with @BeforeUpdate and works fine...

After reading alot of similar github issues, watched youtube tutorials [Hi Ben Awad! :D], I found a somewhat fix.. by using Subscribers

Actually, I don't know what is the difference of the Listener/Subscriber. Maybe I am doing the wrong usage. Can someone enlighten me please? For example the difference of AfterSave of Entity Listener vs AfterSave of Entity Subscriber. When/Best case to use? something like that. Anyway back with the "fix..."

I created a Trip Subscriber:

import { EventSubscriber, EntitySubscriberInterface, InsertEvent } from "typeorm";
import { TripEntity } from "src/trip/trip.entity";

@EventSubscriber()
export class TripSubsriber implements EntitySubscriberInterface<TripEntity> {
    // Denotes that this subscriber only listens to Trip Entity
    listenTo() {
      return TripEntity
    }

    // Called after entity insertion
    async afterInsert(event: InsertEvent<any>) {
        console.log(`AFTER ENTITY INSERTED: `, event.entity);
        const randomString = Math.random().toString(36).substring(2, 15) + Math.random().toString(36).substring(2, 15)
        // query the trip with given event.entity
        const trip = await event.manager.getRepository(TripEntity).findOne(event.entity.id)
        // populate the room with desired format
        trip.room = `${trip.id}_${randomString}`
        // save it!
        await event.manager.getRepository(TripEntity).save(trip)
    }

}

At first it is not working but after digging for hours again, I need to add a subscriber property with the value of the path of my subscribers at the ormconfig.json for it to work! e.g: "subscribers": [ "src/subscriber/*.ts" ]

Again, the Trip Subscriber code seems spaghetti to me because I already have the event.entity object but I do not know how to update it without the need of querying and updating it using event.manager.getRepository(). Please can someone fix this code for me? the proper way of doing it?

NOW, It is working! the request body:

the /api/trips res:

My questions are:

1. Why whenever I use that method methoud subscriber, it is not working. Is it not the proper way to do it? The why is it in the docs? Or for other use case?
2. Do I really have to use subscriber for it to achieve? Thats so many steps.

I came from Rails. So having to create files/subscribers just to do it somewhat tiring. Unlike ActiveRecord's after_save callback it is very easy..

PS. I'm new to nest-js and typeorm