Laravel 4: Select row if a relation exists by querying relation - orm

Question

I am trying to query a products table, and want it to return a collection if a relation exists.
Iteration 1 below queries all rows in the products table, and lazy loads the metals table if $name matches. This is wrong.
My Route:
Route::group(array('prefix' => '{api}/v1'), function()
{
Route::controller('products', 'Api\V1\ProductController');
});
My Controller:
public function getFilter($metal = null) {
$products = $this->product;
if ($metal) {
$products->with('metal', function($query, $metal) {
$query->where('name', $metal);
});
}
return Response::api($products->get());
}
I want only $products to display if metal.name = $metal. e.g. something like:
$this->products->where('metal.name', $metal)->get;
Solution using part of Glad To Help's answer:
This provides an alternative approach 2, without the need for joins.
http://paste.laravel.com/WC4

Answer 1

Unfortunately you cannot do this with one swipe in Eloquent yet.
BUT, there is a way by using the inverse relation, like this:
public function getFilter($metal = null)
{
// filter the metals first
$metals = Metal::with('products')->where('name', '=' , $metal)->get();
$products = array();
foreach($metals as $metal)
{
// collect the products from the filtered metals
$products = array_merge($products, $metal->products->toArray() );
}
return $products;
}
If this is not elegant solution for you, you will either have to use Fluent to construct the query and join the products x metals table manually or pre-join them by overriding the newQuery() method.
1) alternative approach one.
public function getFilter($metal = null) {
return DB::table('products')->join('metal', 'products.id', '=' , 'metal.product_id')
->where('metal.name', $name)
->select(array('products.*'));
}
2) alternative approach two
class Product extends Eloquent{
public function newQuery($excludeDeleted = true){
return parent::newQuery()->join('metal','id','=','metal.product_id');
}
}