Laravel, getting deep relationships

I have the following structure:

'buildings' have many 'blocks' which have many 'units' which have many 'tenants'

I need to get a list of all tenants that live in a building.

Laravel provides hasMany and hasManyThrough commands that help you get collections of models which have direct relationship or are related through a single intermediate table but what if you want to get related elements of two, three, or any levels deep?

What is the proper way to achieve this using Laravel/Eloquent?

To find all the tenants in a given building, the easiest method would be to use JOIN clauses.

I have assumed all of your relationships are hasMany inversed by belongsTo.

$tenants = Tenant::select('tenants.*')
    ->join('units', 'units.id', '=', 'tenant.unit_id')
    ->join('blocks', 'blocks.id', '=', 'units.block_id')
    ->join('buildings', 'buildings.id', '=', 'blocks.building_id')
    ->where('buildings.id', 123)
    ->get();

If this is something you'll use more than once, then I'd suggest creating a query scope on your Tenant model.

class Tenant extends Eloquent
{
    // ...

    public function scopeInBuilding($query, $buildingId)
    {
        return $query->select('tenants.*')
            ->join('units', 'units.id', '=', 'tenant.unit_id')
            ->join('blocks', 'blocks.id', '=', 'units.block_id')
            ->join('buildings', 'buildings.id', '=', 'blocks.building_id')
            ->where('buildings.id', $buildingId);
    }

    // ...
}

And you can use it as follows:

$tenants = Tenant::inBuilding(123)->get();