In Soomla(http://project.soom.la/), they have in-app purchase one liner that looks like this:
[StoreInventory buyItemWithItemId:@"[itemId]"]
However, i'm not sure whether the itemId is the same as the product id defined under iTunes Connect. Can anyone confirm?
The itemId is not the store's productId.
itemId - a unique identifier of an every item defined in your virtual economy (internal use inside SOOMLA). productId - a unique identifier of an every item defined in the App Store. You define it in the developer console.
When you buys something using StoreInventory, use the itemId.