Say I have an orders table and a users table and a guests table, for a company who accept orders from both users and guests.

I also have a is_guest boolean on the orders table which lets me know quickly whether the order has been made by a guest or a registered user.

I have a model method called customer which returns the eloquent relation like so:

public function customer()
{
  return $this->is_guest ? $this->belongsTo('Guest', 'user_id') : $this->belongsTo('User', 'user_id');
}

This works very well when I pass orders to the view and access the customer's data like so:

// Maps to either $order->user->firstname OR $order->guest->firstname
echo $order->customer->firstname;

But when I try to use this functionality when using eager loading it doesn't quite work:

$orders = Order::with('customer')->get();
return Response::make($orders);

It only returns the eager loaded customer data for either the user or the guest and never both.

I'm wondering why this is and how to get round it?

Is it because of the way the eager loading works - it only calls the customer() method once just as it only hits the database once, so whatever the first result of the query is, it will use that to determine the rest of the query too?

If I am trying to get a JSON response of all the order data with all of the customer's details too, how would I do that?

Thanks.

UPDATE

Yes, turns out I was abusing the Laravel relationship method by adding a condition. Using the polymorphic relations is a much better approach as suggested by @lukasgeiter. http://laravel.com/docs/4.2/eloquent#polymorphic-relations

I did have trouble loading other relations based on the polymorphic relation. For example if both User and Guest had corresponding tables UserDetail and GuestDetail then I couldn't get the eager loading to work. So I added this to both the User and Guest models:

protected $with = ['detail'];

This means that whenever the customer polymorphic relation is eager loaded, then both User and Guest will load their relationships automatically. I think I could have also used the 'lazy loading' functionality $order->load('customer') but I didn't try it out.

public function detail()
{
    return $this->hasOne('UserDetail');
}

Thanks guys.