Call to undefined method Illuminate\Database\Eloquent\Relations\BelongsToMany::routeNotificationFor() - laravel

Question

I'm building a messaging system that notifies each user in the conversation when a reply is set.
MessageNotification.php
class MessageNotification extends Notification
{
use Queueable;
/**
* Get the notification's delivery channels.
*
* #param mixed $notifiable
* #return array
*/
public function via($notifiable)
{
return ['database'];
}
public function toArray($notifiable)
{
return [
'data' => 'Messenger notification'
];
}
}
InboxController
public function reply($hashedId, Request $request)
{
$this->validate($request, [
'body' => 'required',
]);
$conversation = Conversation::where('hashed_id', $hashedId)->first();
$users = $conversation->participants();
//dd($conversationUserIds);
$notifications = Notification::send($users, new MessageNotification());
$message = $conversation->messages()->create([
'sender_id' => auth()->user()->id,
'body' => $request->body,
]);
return new MessageResource($message);
}
Error
Call to undefined method Illuminate\Database\Eloquent\Relations\BelongsToMany::routeNotificationFor()
Extra Information
I've had to build a custom Notifiable trait due to needing to use both Laravel Sparks notification system and Laravels stock notification system. Tutorial I got code from.
Custom notification trait
namespace App\Traits;
use Illuminate\Notifications\Notifiable as BaseNotifiable;
use App\Notifications\DatabaseNotification;
trait Notifiable {
use BaseNotifiable;
public function notifications() {
return $this->morphMany(DatabaseNotification::class, 'notifiable')->orderBy('created_at', 'desc');
}
}
Also note that $reciever->notify(new MessageNotification()); works just fine when sending a notification to one user. The only other solution I saw on this was: https://laracasts.com/discuss/channels/code-review/call-to-undefined-method-routenotificationfor-while-sending-email-to-multiple-users
I tried to implement that, but I'm using a database channel so it shouldn't make a difference.

Answer 1

This line here:
$users = $conversation->participants();
Will set the $users variable to a QueryBuilder instance (assuming you are using conventional Laravel relationships), rather than a collection of users. This is because the () at the end of a relationship builds the query but doesn't run it yet. So then when you call Notification::send($users, etc...) you are not passing in a collection of users; you are passing in a QueryBuilder object.
Try this instead:
$users = $conversation->participants;
Again - this is assuming that the participants method on the Conversation model is a standard laravel relationship.