Standard iOS Integration Guide

    Accept payments in iPhone and iPad apps, with built-in support for Apple Pay.

    This guide will take you through building your app's payment flow using STPPaymentContext, a class designed to make building your app's checkout flow as easy as possible. It handles collecting, saving, and reusing your user's payment details, and can also be used to collect shipping info. If you find that this isn't flexible enough for your needs, all of the subcomponents that STPPaymentContext uses under the hood are available for you to use as well. For more on these subcomponents, please read our custom iOS integration guide.

    Prepare your API

    Our prebuilt UI elements operate on the assumption that you have a single Customer object for each of your users. We strongly recommend you create this Customer at the same time you create your user on your own backend, so that every user is guaranteed to have an associated Customer (this is fine even if you don't collect your user's payment information when they sign up — it's totally OK to have a Customer without any attached cards).

    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. 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 should 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 $customerId has been set appropriately from session data
    parse_str($_SERVER['QUERY_STRING'], $params);
    if (!isset($params['api_version']))
    {
        exit(http_response_code(400));
    }
    try {
        $key = \Stripe\EphemeralKey::create(
          array("customer" => $customerId),
          array("stripe_version" => $params['api_version'])
        );
        header('Content-Type: application/json');
        exit(json_encode($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();
      });
    });
    // 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
        }
        key, err := ephemeralkey.New(&stripe.EphemeralKeyParams{
            Customer:      customerId,
            StripeVersion: stripeVersion,
        })
        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'll need a way for your iOS app to communicate with this endpoint. In your app, you should make your API client class conform to the STPEphemeralKeyProvider 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);
        }];
    }

    Implement your app's checkout flow using STPPaymentContext

    Our SDK provides a class called STPPaymentContext, which is designed to make building your app's checkout flow as easy as possible. It handles collecting, saving, and reusing your user's payment details, and can also be used to collect shipping info. Think of it as the data source for your checkout view controller – it handles asynchronously retrieving the data you need, and notifies its delegate when its UI should change. 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.

    Setting the delegate and host view controller

    To work with STPPaymentContext, you'll need to write a class that conforms to STPPaymentContextDelegate. (Note, the code samples in this section are simply examples – your own implementation may differ depending on the structure of your app). STPPaymentContextDelegate has 4 required methods:

    - paymentContextDidChange:

    This method is called, as you might expect, when the payment context's contents change, e.g., when the user selects a new payment method or enters shipping info. This is a good place to update your UI:

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

    - paymentContext:didCreatePaymentResult:completion:

    This method is called when the user has successfully selected a payment method and completed their purchase. You should pass the contents of the paymentResult object to your backend, which should then finish charging your user using the create charge API. 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.

    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);
            }
        }];
    }

    - 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.
    }

    - paymentContext:didUpdateShippingAddress:completion

    If you're using STPPaymentContext to collect shipping info, this method will be 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);
        }
    }

    In addition to setting up your STPPaymentContextDelegate, you'll also need to initialize an STPCustomerContext. You can think of STPCustomerContext as the backing store for STPPaymentContext. A customer context will talk to your backend to retrieve an ephemeral key (via its key provider), and use that key to manage retrieving and updating its Stripe customer on your behalf.

    // MyAPIClient implements STPEphemeralKeyProvider (see above)
    let customerContext = STPCustomerContext(keyProvider: MyAPIClient.sharedClient)
    // MyAPIClient implements STPEphemeralKeyProvider (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 use 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;
    }

    Let your user select their payment method

    When you'd like to give your user the chance to enter or change their payment method (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.presentPaymentMethodsViewController()
    }
    
    // If you prefer a navigation transition
    func choosePaymentButtonTapped() {
        self.paymentContext.pushPaymentMethodsViewController()
    }
    // If you prefer a modal presentation
    - (void)choosePaymentButtonTapped {
        [self.paymentContext presentPaymentMethodsViewController];
    }
    
    // If you prefer a navigation transition
    - (void)choosePaymentButtonTapped {
        [self.paymentContext pushPaymentMethodsViewController];
    }

    This will set up and present an STPPaymentMethodsViewController on the payment context's hostViewController. If the user doesn't have any stored payment methods, it'll automatically prompt them to enter one.

    Let your user enter their shipping info

    When you'd like to give your user the chance 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 (which can also help prevent fraud), or saving it to your own database. When presenting the shipping view controller, you can specify whether you'd like it to be 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.presentShippingViewController()
    }
    // If you prefer a modal presentation
    - (void)choosePaymentButtonTapped {
        [self.paymentContext presentPaymentMethodsViewController];
    }
    
    // If you prefer a navigation transition
    - (void)choosePaymentButtonTapped {
        [self.paymentContext pushPaymentMethodsViewController];
    }

    This will set up and present 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.

    Finishing a 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];
    }

    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.

    Stripe iOS UI Theming

    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.

    More information

    If you'd like more help, we provide an example app that implements all of the code in this tutorial.

    In addition, if you'd like to implement a custom payment flow, all of the sub-components of STPPaymentContext are usable individually. You can read more about them in our custom iOS integration guide.