var productIdentifiers = Set<ProductIdentifier>()
productIdentifiers.insert("product_id_1")
productIdentifiers.insert("product_id_2")

IAP.requestProducts(productIdentifiers) { (response, error) in
	if let products = response?.products where !products.isEmpty {
		// Get the valid products
	   
	} else if let invalidProductIdentifiers = response?.invalidProductIdentifiers {
		// Some products id are invalid
	   
	} else {
		// Some error happened
	}
}

 IAP.purchaseProduct(productIdentifier, handler: { (productIdentifier, error) in
	if let identifier = productIdentifier {
		// The product of 'productIdentifier' purchased.
	     
	} else if let error = error as? NSError {
      if error.code == SKError.Code.paymentCancelled.rawValue {
		// User cancelled
        
      } else {
		// Some error happened
      }
    }
})

 IAP.restorePurchases { (productIdentifiers, error) in
	 if !productIdentifiers.isEmpty {
	 	// Products restored
	   
	 } else if let error = error as? NSError {
       if error.code == SKError.Code.paymentCancelled.rawValue {
	  	// User cancelled
        
       } else {
	  	// Some error happened
       }
      
    } else {
      // No previous purchases were found.
    }
}

IAP.validateReceipt(Constants.IAPSharedSecret) { (statusCode, products) in
	if statusCode == ReceiptStatus.NoRecipt.rawValue {
		// No Receipt in main bundle
	} else {
		// Get products with their expire date.
	}
})