Eloquent: Calling Where on a relation

Question

I have the following Eloquent ORM query.

$products2 = Product::with('metal', 'metal.fixes', 'metal.fixes.currency')
    ->where('metal_id', '=', 1)
    ->get()->toArray();

Output from this query is as follows:

http://pastebin.com/JnDi7swv

I wish to further narrow down my query to only display products where fixes.currency_id = 1.

$products2 = Product::with('metal', 'metal.fixes', 'metal.fixes.currency')
    ->where('metal_id', '=', 1)
    ->where('metal.fixes.currency_id', '=', 1)
    ->get()->toArray();

Could somebody help me with this second where please because I am getting the following error:

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'metal.fixes.currency_id' 
in 'where clause' (SQL: select * from `products` where `metal_id` = ? 
and `metal`.`fixes`.`currency_id` = ?) (Bindings: array ( 0 => 1, 1 => 1, ))

Solved with the help of Rob Gordijn:

$products2 = Product::with(array(
    'metal', 
    'metal.fixes.currency', 
    'metal.fixes' => function($query){
        $query->where('currency_id', '=', 1);
     }))
        ->where('common', '=', 1)
        ->where('metal_id', '=', 1)
        ->get()->toArray();

Answer 1

You are looking for "Eager Load Constraints": http://laravel.com/docs/eloquent#querying-relations

<?php
$products2 = Product::with(array('metal', 'metal.fixes', 'metal.fixes.currency' => function($query){
    $query->where('currency_id', '=', 1);
}))
->where('metal_id', '=', 1)
->get()->toArray();