# Drop flow
Drop flow is the standard flow for Cashfree payment gateway's iOS SDK. In this flow, SDK provides a pre-built native iOS screen to facilitate a quick integration with our payment gateway. Your customers can fill in the necessary details here and complete the payment.
This mode handles all the business logic and UI Components to make the payment smooth and easy to use. The SDK allows the merchant to customize the UI in terms of color coding, fonts and payment modes shown.
# Initiating the payment
To initiate the Drop checkout payment in the SDK, follow these steps
Create a CFSession object.
Create a CFPaymentComponents object.
Create a CFTheme object.
Create a Drop Checkout Payment object.
Set payment callback.
Initiate the payment using the payment object created from [step 4]
## Create a session
order_token`** created from [Step2](🔗) is used to authenticate the payment. The SDK exposes a class **`
CFSession`** class which accepts the order_token, Environment and order ID values.
Cashfree provides two environments, one being the `
sandbox` environment for developers to test the payment flow and responses and the other being `
production` environment which gets shipped to production. This environment can be set in this session object.
The values for environment can be either `
.SANDBOX` or `
## Payment Components
The Cashfree's Drop checkout allows the merchant to control the payment modes shown to their customer using the payment component parameter.
enableComponents()` method takes in an array of string and the order in which the merchant sends the components is honoured. If this method is not called, by default all the payment modes are enabled.
## Set a Theme
CFThemeBuilder` class used to create `
CFTheme` used to set the theming for Drop checkout screen.
## Create a Drop Checkout Payment object
Code Snippet to create a payment object for Drop Checkout (pre-built UI SDK)
If payment component object is not provided then all the payment modes that are enabled for the merchant account is shown.
## Setup payment callback
The SDK exposes a protocol CFResponseDelegate which the class has to conform to. It comes with 2 functions; one of them informs the user to verify the payment and the other informs the user that there was an error while trying to make payment.
@objc func onError(_ error: CFErrorResponse, order_id: String)`
@objc func verifyPayment(order_id: String)`
Code snippet demonstrating it's usage:
# Initiate Payment
Finally to initiate the payment, the above created Payment Object has to be sent to the SDK.
The SDK exposes a class `
CFPaymentGatewayService`, which can be used to set the Payment Object and initiate the payment.
The below code snippet is an example demonstrating it's usage: