Modifying model data before sending response - laravel

Question

I am working on a back-end that needs to re-calculate the price based on user-specific currency.
I fetch all required records from the database as following:
$tasks = Task::with([
'images' => function($query){},
'price' => function($query){},
'user' => function($query){ $query->with('images');},
])->whereDoesntHave('tasksState', function($query) use ($user){
$query->where('user_id', $user->id);
$query->where('state', '<>', 0);
})->where('id', '>', $offset)->where('user_id', '<>', $user->id)->take($limit)->get();
Task's price model consists of currency and value attributes.
Then I iterate through $tasks and re-calculate the price based on the user-specific currency:
foreach ($tasks as $k => $task){
$price = $task->price->value;
$price = $price * $rate->getValue();
$tasks[$k]->price = $price;
//$task->price = $price;
}
After inspecting the tasks, all price are re-calculated correctly.
However when I subsequently serialize $tasks and send it as a response, it contains the data as they were fetched from the database - no re-calculated prices.
Does anybody where is the problem? Any ideas will be greatly appreciated!

Answer 1

Since you're serializing the data anyway, you can first convert collection into an array and work it as with an array:
$tasks->toArray();
In this case you'll be able to override original data as you've tried to accomplish with foreach loop.
As alternative, you could create a mutator which will add calculated_price property to the collection.

Answer 2

You can use Eloquent Mutator for this.
Create following function in Task Model
public function getNewPriceAttribute($value)
{
...// do your processing here
}
And then you can use it as:
$task->new_price;
After creating the accessor, add the attribute name to the appends property on the Task model.
protected $appends = ['new_price'];
Once the attribute has been added to the appends list, it will be included in both the model's array and JSON representations.