Using iOS Standard UI Components

Learn how to accept payments in iOS applications with built-in support for Apple Pay.

The STPPaymentContext class helps you build the checkout flow for your application. It handles collecting, saving, and reusing customer payment details, and can also be used to collect shipping information. It can also serve as the underlying data source for your checkout's view controller. Most importantly, it lets you build a single integration to accept payments via both credit card and Apple Pay instead of having multiple code paths.

To work with STPPaymentContext, you'll need to write a class that conforms to STPPaymentContextDelegate. The code samples in each of the following steps are examples—your own implementation may differ depending on the structure of your app.

To accept payments in your app, you need to:

Set up an ephemeral key
Set up a customer context
Handle the user's payment option
Handle the user's shipping info
Submit the payment

If you find that STPPaymentContext isn't flexible enough for your needs, all of the components are also available to use individually. For more on these components, see Using Custom UI Components.

Step 1: Set up an ephemeral key

In order for our prebuilt UI elements to function, you'll need to provide them with an ephemeral key, a short-lived API key with restricted API access. You can think of an ephemeral key as a session, authorizing the SDK to retrieve and update a specific Customer object for the duration of the session.

Our prebuilt UI elements also operate on the assumption that you have a single Customer object for each of your users. When you create a new user or account on your server, you can create a corresponding Customer object at the same time, even if you don't collect payment information from your users when they sign up. This ensures that your application has a matching Customer for each user.

To provide an ephemeral key to the SDK, you'll need to expose a new API endpoint on your backend. This endpoint should create an ephemeral key for the current Stripe customer, and return the key's unmodified response as JSON. When the SDK requests an ephemeral key, it will specify the version of the Stripe API that it expects the response to come from. Your endpoint must accept an api_version parameter, and use the specified API version when creating the ephemeral key. This ensures that the SDK always receives the correct ephemeral key response from your backend. You can consult our Example Backend to see this in practice.

# Sinatra
post path do
  stripe_version = params['api_version']
  customer_id = session['customer_id']
  key = Stripe::EphemeralKey.create(
    {customer: customer_id},
    {stripe_version: stripe_version}
  )
  key.to_json
end

# Flask
from flask import Flask, session, jsonify, request
# This function assumes that the session handling has stored the customerId
@app.route(path, methods=['POST'])
def issue_key():
    api_version = request.args['api_version']
    customerId = session['customerId']
    key = stripe.EphemeralKey.create(customer=customerId, api_version="2017-05-25")
    return jsonify(key)

// This assumes that $customerId has been set appropriately from session data
if (!isset($_POST['api_version']))
{
    exit(http_response_code(400));
}
try {
    $key = \Stripe\EphemeralKey::create(
      ["customer" => $customerId],
      ["stripe_version" => $_POST['api_version']]
    );
    header('Content-Type: application/json');
    exit(json_encode($key));
} catch (Exception $e) {
    exit(http_response_code(500));
}

// Express
app.post(path, (req, res) => {
  const stripe_version = req.query.api_version;
  if (!stripe_version) {
    res.status(400).end();
    return;
  }
  // This function assumes that some previous middleware has determined the
  // correct customerId for the session and saved it on the request object.
  stripe.ephemeralKeys.create(
    {customer: req.customerId},
    {stripe_version: stripe_version}
  ).then((key) => {
    res.status(200).json(key);
  }).catch((err) => {
    res.status(500).end();
  });
});

// Using Spark framework (http://sparkjava.com)
post(new Route(path) {
    @Override
    public Object handle(final Request request,
                         final Response response) {
        String apiVersion = request.queryParams("api_version");
        RequestOptions requestOptions = (new RequestOptions.RequestOptionsBuilder())
                                          .setStripeVersion(apiVersion)
                                          .build();

        try {
            // Retrieve the customer id from your session for example
            Map<String, Object> options = new HashMap<String, Object>();
            options.put("customer", customerId);

            EphemeralKey key = EphemeralKey.create(options, requestOptions);
            return key.getRawJson();
        } catch (StripeException e) {
            response.status(500);
            return e;
        }
    }
});

// net/http
// The customerId parameter should be the ID of the Customer object associated
// with the session the request was made on.
func issueKeyHandler(w http.ResponseWriter, r *http.Request, customerId string) {
    r.ParseForm()
    stripeVersion := r.Form.Get("api_version")
    if stripeVersion == "" {
        log.Printf("Stripe-Version not found\n")
        w.WriteHeader(400)
        return
    }
    params := &stripe.EphemeralKeyParams{
        Customer: stripe.String(customerId),
        StripeVersion: stripe.String(stripeVersion),
    }
    key, err := ephemeralkey.New(params)
    if err != nil {
        log.Printf("Stripe bindings call failed, %v\n", err)
        w.WriteHeader(500)
        return
    }
    w.Write(key.RawJSON)
}

After you've added an ephemeral key endpoint to your backend, you need to set up a way for your iOS app to communicate with this endpoint. In your app, you should make your API client class conform to the STPCustomerEphemeralKeyProvider protocol, which defines a single method, createCustomerKeyWithAPIVersion. When implementing this method, be sure to pass the apiVersion parameter along to your ephemeral keys endpoint. You can consult our Example App to see this in practice.

func createCustomerKey(withAPIVersion apiVersion: String, completion: @escaping STPJSONResponseCompletionBlock) {
    let url = self.baseURL.appendingPathComponent("ephemeral_keys")
    Alamofire.request(url, method: .post, parameters: [
        "api_version": apiVersion
        ])
        .validate(statusCode: 200..<300)
        .responseJSON { responseJSON in
            switch responseJSON.result {
            case .success(let json):
                completion(json as? [String: AnyObject], nil)
            case .failure(let error):
                completion(nil, error)
            }
    }
}

- (void)createCustomerKeyWithAPIVersion:(NSString *)apiVersion completion:(STPJSONResponseCompletionBlock)completion {
    NSURL *url = [self.baseURL URLByAppendingPathComponent:@"ephemeral_keys"];
    AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
    [manager POST:url.absoluteString
       parameters:@{@"api_version": apiVersion}
         progress:nil
          success:^(NSURLSessionDataTask *task, id responseObject) {
        completion(responseObject, nil);
    } failure:^(NSURLSessionDataTask *task, NSError *error) {
        completion(nil, error);
    }];
}

Step 2: Set up a customer context

In addition to setting up your STPPaymentContextDelegate, you'll also need to initialize an STPCustomerContext. The STPCustomerContext is like the backing store for STPPaymentContext. A customer context retrieves and updates its Stripe customer using an ephemeral key obtained from your server via its key provider.

// MyAPIClient implements STPCustomerEphemeralKeyProvider (see above)
let customerContext = STPCustomerContext(keyProvider: MyAPIClient.sharedClient)

// MyAPIClient implements STPCustomerEphemeralKeyProvider (see above)
STPCustomerContext *customerContext = [[STPCustomerContext alloc] initWithKeyProvider:[MyAPIClient sharedInstance]];

STPCustomerContext will automatically prefetch its customer once its key provider has been set. If you'd like to take advantage of preloading your customer's information, you should initialize your STPCustomerContext instance earlier, before your user enters your payment flow.

If your current user logs out of the app and a new user logs in, be sure to either create a new instance of STPCustomerContext, or clear the cached customer using the provided clearCachedCustomer method. On your backend, be sure to create and return a new ephemeral key for the Customer object associated with the new user.

Once you've set up your customer context, you can use it to initialize STPPaymentContext. Be sure to set your payment context's delegate and hostViewController properties (these will usually be the same object, a UIViewController instance). You should also set the payment context's paymentAmount property, which will be displayed to your user in the Apple Pay dialog (you can change this later, if the amount of the user's purchase changes).

init() {
    self.paymentContext = STPPaymentContext(customerContext: customerContext)
    super.init(nibName: nil, bundle: nil)
    self.paymentContext.delegate = self
    self.paymentContext.hostViewController = self
    self.paymentContext.paymentAmount = 5000 // This is in cents, i.e. $50 USD
}

- (instancetype)init {
    self = [super initWithNibName:nil bundle:nil];
    if (self) {
       self.paymentContext = [[STPPaymentContext alloc] initWithCustomerContext:customerContext]];
       self.paymentContext.delegate = self;
       self.paymentContext.hostViewController = self;
       self.paymentContext.paymentAmount = 5000 // This in cents, i.e. $50 USD
    }
    return self;
}

Step 3: Handle the user's payment option

When you'd like to give your user the chance to enter or change their payment option (say, they tapped a button on your checkout page that lets them do this), STPPaymentContext can do this for you automatically. You can specify whether you'd like the payment selector view controller to be presented modally, or pushed onto a UINavigationController stack:

// If you prefer a modal presentation
func choosePaymentButtonTapped() {
    self.paymentContext.presentPaymentOptionsViewController()
}

// If you prefer a navigation transition
func choosePaymentButtonTapped() {
    self.paymentContext.pushPaymentOptionsViewController()
}

// If you prefer a modal presentation
- (void)choosePaymentButtonTapped {
    [self.paymentContext presentPaymentOptionsViewController];
}

// If you prefer a navigation transition
- (void)choosePaymentButtonTapped {
    [self.paymentContext pushPaymentOptionsViewController];
}

This sets up and presents an STPPaymentOptionsViewController on the payment context's hostViewController. If the user doesn't have any stored payment options, it automatically prompts them to enter one.

`- paymentContextDidChange:`

This method triggers when the content of the payment context changes, like when the user selects a new payment method or enters shipping information. This is a good place to update your UI:

func paymentContextDidChange(_ paymentContext: STPPaymentContext) {
    self.activityIndicator.animating = paymentContext.loading
    self.paymentButton.enabled = paymentContext.selectedPaymentOption != nil
    self.paymentLabel.text = paymentContext.selectedPaymentOption?.label
    self.paymentIcon.image = paymentContext.selectedPaymentOption?.image
}

- (void)paymentContextDidChange:(STPPaymentContext *)paymentContext {
    self.activityIndicator.animating = paymentContext.loading;
    self.paymentButton.enabled = paymentContext.selectedPaymentOption != nil;
    self.paymentLabel.text = paymentContext.selectedPaymentOption.label;
    self.paymentIcon.image = paymentContext.selectedPaymentOption.image;
}

Step 4: Handle the user's shipping info

If your user needs to enter or change their shipping address and shipping method, STPPaymentContext can do this for you automatically. STPPaymentContext will save shipping info to the Stripe customer when your user updates their information, and automatically prefill the shipping view controller for future purchases. Note that you should not rely on the shipping information stored on the Stripe customer for order fulfillment, as your user may change this information if they make multiple purchases. We recommend adding shipping information when you create a Charge or PaymentIntent object (which can also help prevent fraud), or when saving it to your own database. When presenting the shipping view controller, you can specify whether you'd like it presented modally, or pushed onto a UINavigationController stack:

// If you prefer a modal presentation
func shippingButtonTapped() {
    self.paymentContext.presentShippingViewController()
}

// If you prefer a navigation transition
func shippingButtonTapped() {
    self.paymentContext.pushShippingViewController()
}

// If you prefer a modal presentation
- (void)shippingButtonTapped {
    [self.paymentContext presentShippingViewController];
}

// If you prefer a navigation transition
- (void)shippingButtonTapped {
    [self.paymentContext pushShippingViewController];
}

This sets up and presents an STPShippingAddressViewController on the payment context's hostViewController. Once the user enters a valid shipping address, they'll be taken to an STPShippingMethodsViewController. After they select a shipping method, both view controllers will be dismissed or popped off the hostViewController's stack.

`- paymentContext:didUpdateShippingAddress:completion:`

This method is called after your user enters a shipping address. Here, you should validate the returned address and determine the shipping methods available for that address. If the address is valid, you should call the provided completion block with a status of STPShippingStatusValid, nil for the error argument, an array of shipping methods, and a selected shipping method. If you don't need to collect a shipping method, you should just pass nil for the shipping methods and selected shipping method. If the address is invalid, you should call the completion block with a status of STPShippingStatusInvalid, an error object describing the issue with the address, and nil for the shipping methods and selected shipping method. Note that providing an error object is optional—if you omit it, the user will simply see an alert with the message "Invalid Shipping Address".

func paymentContext(_ paymentContext: STPPaymentContext, didUpdateShippingAddress address: STPAddress, completion: @escaping STPShippingMethodsCompletionBlock) {
    let upsGround = PKShippingMethod()
    upsGround.amount = 0
    upsGround.label = "UPS Ground"
    upsGround.detail = "Arrives in 3-5 days"
    upsGround.identifier = "ups_ground"
    let fedEx = PKShippingMethod()
    fedEx.amount = 5.99
    fedEx.label = "FedEx"
    fedEx.detail = "Arrives tomorrow"
    fedEx.identifier = "fedex"

    if address.country == "US" {
        completion(.valid, nil, [upsGround, fedEx], upsGround)
    }
    else {
        completion(.invalid, nil, nil, nil)
    }
}

- (void)paymentContext:(STPPaymentContext *)paymentContext didUpdateShippingAddress:(STPAddress *)address completion:(STPShippingMethodsCompletionBlock)completion {
    PKShippingMethod *upsGround = [PKShippingMethod new];
    upsGround.amount = [NSDecimalNumber decimalNumberWithString:@"0"];
    upsGround.label = @"UPS Ground";
    upsGround.detail = @"Arrives in 3-5 days";
    upsGround.identifier = @"ups_ground";
    PKShippingMethod *fedEx = [PKShippingMethod new];
    fedEx.amount = [NSDecimalNumber decimalNumberWithString:@"5.99"];
    fedEx.label = @"FedEx";
    fedEx.detail = @"Arrives tomorrow";
    fedEx.identifier = @"fedex";
    if ([address.country isEqualToString:@"US"]) {
        completion(STPShippingStatusValid, nil, @[upsGround, fedEx], upsGround);
    }
    else {
        completion(STPShippingStatusInvalid, nil, nil, nil);
    }
}

Step 5: Submit the payment

Finally, when your user taps "Buy", just call requestPayment on your payment context. It'll display any required UI (such as the Apple Pay dialog) and call the appropriate methods on its delegate as your user finishes their payment.

func payButtonTapped() {
    self.paymentContext.requestPayment()
}

- (void)payButtonTapped {
    [self.paymentContext requestPayment];
}

`- paymentContext:didCreatePaymentResult:completion:`

This method is called when the user has successfully selected a payment method and completed their purchase.

Pass the contents of the paymentResult object to your backend, which should then finish charging your user using the Charge object.

func paymentContext(_ paymentContext: STPPaymentContext,
  didCreatePaymentResult paymentResult: STPPaymentResult,
  completion: @escaping STPErrorBlock) {

  myAPIClient.createCharge(paymentResult.source.stripeID, completion: { (error: Error?) in
      if let error = error {
          completion(error)
      } else {
          completion(nil)
      }
  })
}

- (void)paymentContext:(STPPaymentContext *)paymentContext
didCreatePaymentResult:(STPPaymentResult *)paymentResult
            completion:(STPErrorBlock)completion {
    [self.apiClient createCharge:paymentResult.source.stripeID completion:^(NSError *error) {
        if (error) {
            completion(error);
        } else {
            completion(nil);
        }
    }];
}

Pass the contents of the paymentResult object to your backend, which should then finish charging your user using the PaymentIntent object and manual confirmation. See Using Payment Intents on iOS for more information on handling required actions and redirects.

func paymentContext(_ paymentContext: STPPaymentContext,
  didCreatePaymentResult paymentResult: STPPaymentResult,
  completion: @escaping STPErrorBlock) {

    myAPIClient.createAndConfirmPaymentIntent(paymentResult.source.stripeID,
                                              amount: paymentContext.paymentAmount,
                                              returnURL: "your-app://stripe-redirect",
                                              shippingAddress: paymentContext.shippingAddress,
                                              shippingMethod: paymentContext.selectedShippingMethod) { (paymentIntent: STPPaymentIntent?, error: Error?) in
                                                if error != nil {
                                                  completion(error)
                                                } else if let paymentIntent = paymentIntent {

                                                  if paymentIntent.status == .requiresAction {
                                                    self.performAction(for: paymentIntent, completion: completion)
                                                  } else {
                                                    // successful
                                                    completion(nil)
                                                  }
                                                } else {
                                                  let err: Error = ... // report error from your API
                                                  completion(err)
                                                }
                                              }
}

- (void)paymentContext:(STPPaymentContext *)paymentContext
didCreatePaymentResult:(STPPaymentResult *)paymentResult
            completion:(STPErrorBlock)completion {
    [self.apiClient createAndConfirmPaymentIntentWithSource:paymentResult.source.stripeID
                                                     amount:paymentContext.paymentAmount
                                                  returnURL:@"your-app://stripe-redirect"
                                            shippingAddress:paymentContext.shippingAddress
                                             shippingMethod:paymentContext.selectedShippingMethod
                                                 completion:^(STPPaymentIntent * _Nullable paymentIntent, NSError * _Nullable error) {
                                                       if (error != nil) {
                                                         completion(error);
                                                       } else if (paymentIntent == nil) {
                                                         NSError *apiError = ... // report error from your API
                                                         completion(apiError);
                                                       } else if (paymentIntent.status == STPPaymentIntentStatusRequiresAction) {
                                                         [self _performActionForPaymentIntent:paymentIntent completion:completion];
                                                       } else {
                                                         // success
                                                         completion(nil);
                                                       }
                                                    }];
}

When this API request is finished, call the provided completion block with nil as its only argument if the call succeeded, or, if an error occurred, with that error as the argument instead.

`- paymentContext:didFinishWithStatus:error:`

This method is called after the previous method, when any auxiliary UI that has been displayed (such as the Apple Pay dialog) has been dismissed. You should inspect the returned status and show an appropriate message to your user. For example:

func paymentContext(_ paymentContext: STPPaymentContext,
  didFinishWithStatus status: STPPaymentStatus,
  error: Error?) {

    switch status {
    case .error:
        self.showError(error)
    case .success:
        self.showReceipt()
    case .userCancellation:
        return // Do nothing
    }
}

- (void)paymentContext:(STPPaymentContext *)paymentContext
   didFinishWithStatus:(STPPaymentStatus)status
                 error:(NSError *)error {
    switch (status) {
        case STPPaymentStatusSuccess:
            [self showReceipt];
        case STPPaymentStatusError:
            [self showError:error];
        case STPPaymentStatusUserCancellation:
            return; // Do nothing
    }
}

`- paymentContext:didFailToLoadWithError:`

This method is called in the rare case that the payment context's initial loading call fails, usually due to lack of internet connectivity. You should dismiss your checkout page when this occurs and invite the user to try again. You can also optionally attempt to try again by calling retryLoading on the payment context.

func paymentContext(_ paymentContext: STPPaymentContext,
  didFailToLoadWithError error: Error) {
    self.navigationController?.popViewController(animated: true)
    // Show the error to your user, etc.
}

- (void)paymentContext:(STPPaymentContext *)paymentContext didFailToLoadWithError:(NSError *)error {
     [self.navigationController popViewControllerAnimated:YES];
     // Show the error to your user, etc.
}

Customizing the look-and-feel of Stripe UI elements

We built the payment selector so that you can define your own appearance and apply the attributes you want to customize from the default theme that we provide.

You can override any of the properties from the default theme, typically in your AppDelegate:

STPTheme.default().accentColor = UIColor.blue

[[STPTheme defaultTheme] setAccentColor:[UIColor blueColor]];

Here is a list of properties you can customize and their respective usage inside the payment selector UI:

Property Name	Description
`primaryBackgroundColor`	Background color for any views in this theme
`secondaryBackgroundColor`	Background color for any supplemental views inside a view (for example the cells of a table view)
`primaryForegroundColor`	Text color for any important labels in a view
`secondaryForegroundColor`	Text color for any supplementary labels in a view
`accentColor`	Color for any buttons and other elements on a view that are important to highlight
`errorColor`	Color for rendering any error messages or views
`font`	Font to be used for all views
`emphasisFont`	Medium-weight font to be used for all bold text in views

We also let you customize all the fonts used in this payment selector flow. By default, the SDK will use the system font at different weight and sizes. To override the defaults, set the font and emphasisFont properties and the SDK will automatically use your choice instead and infer the rest.

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