Laravel Eloquent: Best Way to Calculate Total Price

Question

Im building a simple buy and sell application with Laravel 5.1. Each Buy Model has many BuyDetail which stores bought item quantity and buy_price. I have implement the relations

Answer 1

I realise an answer’s already been accepted, but just thought I’d add my own detailing another approach.

Personally, I like to put “aggregate” methods like these on custom collection classes. So if I have a Buy model that can have many BuyDetail models, then I would put a getTotal() method on my BuyDetailCollection method like this:

use Illuminate\Database\Eloquent\Collection as EloquentCollection;

class BuyDetailCollection extends EloquentCollection
{
    public function getTotal()
    {
        return $this->items->sum(function ($detail) {
            return $detail->price * $detail->quantity;
        });
    }
}

I can then add this to the BuyDetail model:

class BuyDetail extends Model
{
    public function newCollection(array $models = [])
    {
        return new BuyDetailCollection($models);
    }
}

And use my getTotal() method where ever I need to now:

$buy = Buy::with('buyDetails')->find($id);

$total = $buy->buyDetails->getTotal();