Laravel - Form - Eager Loading - forms

Question

Hi I'm working on a CRUD interface to update an Event.
Event Class Model a Event belongs to many Organizer
class Event extends Model
{
public function organizers()
{
return $this->belongsToMany('App\Organizer')->withTimestamps();
}
}
Organizer Class Model
class Organizer extends Model
{
public function event()
{
return $this->belongsToMany('App\Event')->withTimestamps();
}
}
Event controller I send the event along with its organizer(s)
public function edit($id)
{
$event = Event::with(['organizers'])->findOrFail($id);
return view('event.edit', ['event' => $event]);
}
event.edit view
<? $organizers = DB::table('organizers')->lists('name', 'id'); ?>
{!! Form::model($event, [
'method' => 'PATCH',
'route' => ['eventUpdate', $event->id]
]) !!}
<div id="organizer_id-group" class="form-group">
{{Form::select('organizer[id]', $organizers, null,['class'=>'form-control'])}}
</div>
{!! Form::submit('Update', ['class' => 'btn btn-primary']) !!}
{!! Form::close() !!}
For the moment I see the whole list of organizers which is good but the default value, or the selected one does not correspond to the one linked to the event.
I tried
<div id="organizer_id-group" class="form-group">
#foreach($event->organizers as $key =>$organizer)
{{Form::select($organizer->id, $organizers, null,['class'=>'form-control'])}}
#endforeach
</div>
but the selected organizer is always the first even if $organizer->id = 2
Any help would be welcome. Thank you

Answer 1

When working with Form::model it could be easier to work with the name of the property in the database.
If you have
{{Form::select('organizer[id]', $organizers, null,['class'=>'form-control'])}}
Then the value of the form will be set to $event->organizer->id if it exists.
Also from your use case it looks like an organizer belongsTo an event. You do not show the organizer model, but inside the event model you define a many-to-many relationship. This implies that you have $event->organizers.
From the information available you might want to change the relationship to
return $this->belongsTo('App\Organizer');
Amendment / Update (after additional information)
It is clear now, you are indeed working with a many-to-many collection. I have not managed to get Form model binding to work with belongsToMany collections so you need to set the 3rd parameter to physically define the organizers that need to be selected.
The most elegant way I know about is to define an accessor on your Event object for the event organizer ids. This way you can use a call to old for a validation error and then define a default as well which are the values for the initial edit.
Notice that in the form we are using an array for the multiple values.
{{Form::select('organizers[]', $organizers, old('organizers', $event->organizers_ids), ['class' => 'form-control', 'multiple'])}}
Then inside your Model you add the accessor to return the ids.
public function getOrganizersIdsAttribute()
{
return $this->organizers->lists('id')->all();
}

Answer 2

Answer# Update after Leon suggestions
This is what I needed to do to make it works
<div id="organizer_id-group" class="form-group">
{{Form::select('organizers[]', $organizers, $event->organizers->lists('id')->all(),['class'=>'form-control', 'multiple'])}}
<span class="help-block"></span>
</div>
To make a selection by default you have to change the third argument (https://laravelcollective.com/docs/5.0/html#opening-a-form)