Laravel Eloquent 'withCount' function on multiple joined tables

Question

I have multiple hasMany relations where I want the row count only for the last table.

Users can register for workshops at a specific date and time, so the relations look like 'Workshop' -> hasMany 'Date' -> hasMany 'TimeSlot' -> hasMany 'Registration'.

//Workshop Model
public function workshop_dates(){
  return $this->hasMany(WorkshopDate::class);
}

//Date Model
public function workshops(){
  return $this->belongsTo(Workshop::class);
}
public function workshop_times(){
  return $this->hasMany(WorkshopTime::class);
}

//Time Model
public function workshop_dates(){
  return $this->belongsTo(WorkshopDate::class);
}
public function registrations(){
  return $this->hasMany(Registration::class);
}

//Registration Model
public function workshop_times(){
  return $this->belongsTo(WorkshopTime::class, 'workshop_time_id','id');
}

In my controller I fetch all workshops with all related dates and timelots, but I don't want the user to download all the registration data. I only want them to download the number of registrations for each timeslot. I tried with the 'withCount' function:

return Workshop::with('workshop_dates.workshop_times.registrations')->withCount('registrations')

But this gave me the error 'Call to undefined method App\Workshop::registrations()'

So I created this method in Workshop.php, with the extended version of hasManyThrough:

public function registrations(){
  return $this->hasManyDeep(Registration::class, [WorkshopDate::class,WorkshopTime::class]);
}

However, now I get the total number of registrations per workshop in stead of per timeslot.

I'm a laravel beginner and searching for a solution for many hours. All help is appreciated!

senty senty · Accepted Answer · 2019-12-27T12:53:53

You can add the withCount() on relationship with a closure like this:

Workshop::with(['workshop_dates.workshop_times' => function($q) {
            $q->withCount('registrations');                      
   }, 'workshop_dates.workshop_times.registrations'])
   ->get()

Otherwise, something like this approach https://stackoverflow.com/a/41166325/4705339

Laravel Eloquent 'withCount' function on multiple joined tables

1 Answers