Unable to assign variable value in model constructor - php

Question

I am playing with Laravel models and I need one to return a value that is not in the db table but it comes by running a model method. This method runs a query that groups and count grouped results.
The model method works just fine but I don't seem to be able to pre-fill the $quantity variable within the constructor with something different than 0.
So this is an excerpt of the model:
public $quantity;
function __construct($attributes = array(), $exists = false) {
parent::__construct($attributes, $exists);
$this->quantity = $this->quantity();
}
public function quantity()
{
$query = DB::table('carts_shopping')
->select('cart_id', DB::raw('COUNT(*) AS quantity'))
->where('cart_id',$this->cart_id)
->groupBy('cart_id')
->first();
return ($query) ? $query->quantity : 0;
}
While this is how I am trying to retrieve the results from controller:
$cartitems = Auth::user()->cartshopping;
foreach ($cartitems as $cartitem)
{
echo $cartitem->name;
echo $cartitem->quantity;
}
As you may guess 'cartshopping' comes from the user model being related with the model excerpt I pasted.
I also noticed that quantity() method gets called and it returns 0 all the time as if $this->cart_id was empty and, changing $this-cart_id with a real value the query itself doesn't even get executed.
Thanks a lot for any suggestion you guys can share.

Answer 1

Have you tried accessing the properties using $this->attributes?
public $quantity;
function __construct($attributes = array(), $exists = false) {
parent::__construct($attributes, $exists);
$this->quantity = $this->quantity();
}
public function quantity() {
$query = DB::table('carts_shopping')
->select('cart_id', DB::raw('COUNT(*) AS quantity'))
->where('cart_id', $this->attributes['cart_id'])
->groupBy('cart_id')
->first();
return ($query) ? $query->quantity : 0;
}
Failing that, you could try using the Eloquent accessors, which would be the best way to do it. This would make it dynamic as well, which could be useful.
class YourModel {
// Normal model data here
public function getQuantityAttribute() {
$query = DB::table('carts_shopping')
->select('cart_id', DB::raw('COUNT(*) AS quantity'))
->where('cart_id', $this->attributes['cart_id'])
->groupBy('cart_id')
->first();
return ($query) ? $query->quantity : 0;
}
}