After investigating further, I discovered that when querying products in store-kit, SKProduct returns with a property named priceLocale, which consists of the country code and currency code. The country code of priceLocale seems to be consistent with the user's app store.
To sum up, doing these steps will get the result, however in a slow and not straightforward way:
- Define an in-app item;
- Query that item in your app;
- Determine user's country according to [product.priceLocale objectForKey:NSLocaleCountryCode];
- Show the user the relevant products your app supports in their country.