purchaseProduct
abstract fun purchaseProduct(productID: String, opts: Double = definedExternally): Promise<Boolean>(source)
abstract fun purchaseProduct(productID: String, opts: PurchaseProductOpts = definedExternally): Promise<Boolean>(source)
Returns true if the product is valid and added to the payment queue.
You should listen for the transactions-updated event as soon as possible and certainly before you call purchaseProduct.