Q:

Storekit: How to check if the product is purchased or not?

I think everyone knows that Apple In-App Purchases are a little bit difficult thing to implement. (Especially for Swift newbies).
Anyway, I tried to learn working with it. Maybe it's better to say that I followed the tutorial Kilo Loco made on YouTube. 
Here
I did everything what he did and it's working but it's obvious that I don't understand everything yet.
My question is.. how to check if the customer already purchased it or not?
Maybe there's some kind of status? 
Then I would just write something like that:
if(status=="purchased")
{
   // I would do something what premium user can do.
}

I know it's not really clear but I guess who have more experience in it can help me to understand more. (or maybe I should go watch tutorial once again and once again)
THANK YOUU!

A:

You can check this tutorial, the section about Purchased Items.
In short, you should save locally if the Item has been already purchased, maybe in UserDefaults
A more secure alternative is to validate the receipt of the purchase, as shown in the Apple Documentation. 

