A SKStoreProductViewController object presents a store that allows the user to purchase other media from the App Store. For example, your app might display the store to allow the user to purchase another app.
To display a store, create a new SKStoreProductViewController object and set its delegate. Then, present the view controller modally from another view controller in your app. Your delegate dismisses the view controller when the user completes the purchase.
To choose a specific product, call the loadProductWithParameters:completionBlock: method, passing the iTunes item identifier for the item you want to sell.