> ## Documentation Index
> Fetch the complete documentation index at: https://primer.io/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# configure

Configuring Universal Checkout is as easy as implementing one line of code.
Note that there are more settings which can be passed to Universal Checkout.
Please refer to the section below for more information.

```swift SWIFT theme={"dark"}
func configure(settings: PrimerSettings? = nil, delegate: PrimerDelegate? = nil)
```

## Parameters

<Expandable title="Parameters" defaultOpen>
  <ResponseField name="settings" type="PrimerSettings" required>
    <Expandable title="Properties" defaultOpen>
      <ResponseField name="paymentHandling" type="enum PrimerPaymentHandling">
        Use this to set you payment handling flow. Defaults to `.auto`.

        <Expandable title="Cases" defaultOpen>
          <ResponseField name="auto" type="default">
            Primer SDK will create the payment and handle the flow.
          </ResponseField>

          <ResponseField name="manual">
            If you use the manual flow, make sure you add the `primerDidTokenizePaymentMethod(_:decisionHandler:)` delegate function of `PrimerDelegate`, create a payment on your backend and call the `decisionHandler` of the delegate function once you receive your backend's response.
          </ResponseField>
        </Expandable>
      </ResponseField>

      <ResponseField name="localeData" type="PrimerLocaleData">
        Forces some payment methods' locale.

        <Expandable title="Properties" defaultOpen>
          <ResponseField name="languageCode" type="String" required>
            Forces the language code (e.g. `en`). Defaults on your app's language code if available.
          </ResponseField>

          <ResponseField name="regionCode" type="String">
            Forces the language code (e.g. `US`). Defaults on your app's region code if available.
          </ResponseField>
        </Expandable>
      </ResponseField>

      <ResponseField name="paymentMethodOptions" type="PrimerPaymentMethodOptions">
        <Expandable title="Properties" defaultOpen>
          <ResponseField name="urlScheme" type="String">
            ⚠️ Required for some payment methods (e.g. PayPal). <br /><br />This option sets the deeplink schema used when redirecting back from 3rd party applications to your app.
          </ResponseField>

          <ResponseField name="applePayOptions" type="PrimerApplePayOptions">
            ⚠️ Required when using Apple Pay in your integration.

            <Expandable title="Properties" defaultOpen>
              <ResponseField name="merchantIdentifier" type="String" required>
                Set it to the merchant identifier as it is shown in your Apple Pay
                certificate.
              </ResponseField>

              <ResponseField name="merchantName" type="String" deprecated>
                Set it to the merchant name that you want to be shown on the Apple Pay screen. Deprecated, use [ClientSession](/api-reference/v2.4/api-reference/client-session-api/create-a-client-session) instead.
              </ResponseField>

              <ResponseField name="isCaptureBillingAddressEnabled" type="Bool">
                Defaults to `false`. Set to `true` to let Apple Pay capture the customer's billing address.

                Use BillingOptions to configure required billing fields.
              </ResponseField>

              <ResponseField name="showApplePayForUnsupportedDevice" type="Bool">
                If in some cases you don't want to present ApplePay option if the device is not supporting it set this to `false`. The default value is `true`.

                Default value is `true`. Set to `false` if you do not want to present
                Apple Pay option on unsupported devices.
              </ResponseField>

              <ResponseField name="checkProvidedNetworks" type="Bool">
                Flag introduced to enable the initiation of the ApplePay flow even when no cards are present in the Wallet. To enable the feature, set this to `false`. The default value `true`.

                Default value is `true`. This flag supports the old behavior where Apple
                Pay flow might not present if there are no cards in the Wallet.
              </ResponseField>

              <ResponseField name="shippingOptions" type="ShippingOptions">
                Configure shipping options for Apple Pay.

                <Expandable title="Properties" defaultOpen>
                  <ResponseField name="shippingContactFields" type="Array of RequiredContactField">
                    Specify which contact fields are required for shipping.
                  </ResponseField>

                  <ResponseField name="requireShippingMethod" type="Bool">
                    Indicate if a shipping method is required.
                  </ResponseField>
                </Expandable>
              </ResponseField>

              <ResponseField name="billingOptions" type="BillingOptions">
                Configure billing options for Apple Pay.

                <Expandable title="Properties" defaultOpen>
                  <ResponseField name="requiredBillingContactFields" type="Array of RequiredContactField">
                    Specify which contact fields are required for billing.
                  </ResponseField>
                </Expandable>
              </ResponseField>
            </Expandable>
          </ResponseField>

          <ResponseField name="klarnaOptions" type="PrimerKlarnaOptions">
            ⚠️ Required when using Klarna in your integration.

            <Expandable title="Properties" defaultOpen>
              <ResponseField name="recurringPaymentDescription" type="String" required>
                Set the payment description that will be shown on the Klarna screen.
              </ResponseField>
            </Expandable>
          </ResponseField>

          <ResponseField name="threeDsOptions" type="PrimerThreeDsOptions">
            <Expandable title="Properties" defaultOpen>
              <ResponseField name="threeDsAppRequestorUrl" type="String">
                Set the [iOS Universal Link](https://developer.apple.com/ios/universal-links/) that's used to call your app after an **out-of-band (OOB)** authentication.
                Supported in 3D Secure protocol versions 2.2.0 and after.
              </ResponseField>
            </Expandable>
          </ResponseField>

          <ResponseField name="stripeOptions" type="PrimerStripeOptions">
            ⚠️ Required when using Stripe ACH in your integration.

            <Expandable title="Properties" defaultOpen>
              <ResponseField name="publishableKey" type="String?">
                Set the [Stripe publishable key](https://docs.stripe.com/keys#obtain-api-keys/).
              </ResponseField>

              <ResponseField name="mandateData" type="MandateData?">
                One of:

                <Expandable title="Options" defaultOpen>
                  <ResponseField name="fullMandate(text:)" type="MandateData">
                    The full `text` that you would like to be displayed to the user before
                    they accept/decline the mandate.
                  </ResponseField>

                  <ResponseField name="templateMandate(merchantName:)" type="MandateData">
                    A `merchantName` that will be used as part of our predefined mandate template.
                  </ResponseField>
                </Expandable>
              </ResponseField>
            </Expandable>
          </ResponseField>
        </Expandable>
      </ResponseField>

      <ResponseField name="uiOptions" type="PrimerUIOptions">
        Set the `uiOptions` for custom UI options of the Primer SDK.

        <Expandable title="Properties" defaultOpen>
          <ResponseField name="isInitScreenEnabled" type="Bool">
            Set to `false` to hide the loading screen before the Universal Checkout or the Vault Manager. Defaults to `true`.
          </ResponseField>

          <ResponseField name="isSuccessScreenEnabled" type="Bool">
            Set to `false` to hide the screen after a successful payment, or tokenization on the vault flow. Defaults to `true`.
          </ResponseField>

          <ResponseField name="isErrorScreenEnabled" type="Bool">
            Set to `false` to hide the error screen when an error occurs. Defaults to `true`.
          </ResponseField>

          <ResponseField name="dismissalMechanism" type="enum DismissalMechanism">
            Set the mechanism for dismissing Universal Checkout. Options are:

            * `gestures`: The dialog can be dismissed by tapping outside or by swiping down.
            * `closeButton`: A close button is provided, allowing users to dismiss the dialog manually.
          </ResponseField>

          <ResponseField name="theme" type="PrimerTheme">
            Set a custom theme for Primer SDK.
          </ResponseField>

          <ResponseField name="appearanceMode" type="enum PrimerAppearanceMode">
            Control the SDK's appearance mode independently of the system setting. This allows apps to force light or dark mode regardless of the device's appearance setting.

            <Expandable title="Cases" defaultOpen>
              <ResponseField name="system" type="default">
                Follow the system's appearance setting (default behavior).
              </ResponseField>

              <ResponseField name="light">
                Force light mode appearance regardless of system setting.
              </ResponseField>

              <ResponseField name="dark">
                Force dark mode appearance regardless of system setting.
              </ResponseField>
            </Expandable>
          </ResponseField>

          <ResponseField name="cardFormUIOptions" type="PrimerCardFormUIOptions?">
            Configure the card form UI options.

            <Expandable title="Properties" defaultOpen>
              <ResponseField name="payButtonAddNewCard" type="Bool">
                When set to true, the Drop-In's card form pay button will show "Add new card"; otherwise it will show "Pay \$x.xx".
              </ResponseField>
            </Expandable>
          </ResponseField>
        </Expandable>
      </ResponseField>

      <ResponseField name="debugOptions" type="PrimerDebugOptions">
        <Expandable title="Properties" defaultOpen>
          <ResponseField name="is3DSSanityCheckEnabled" type="Bool" required />
        </Expandable>
      </ResponseField>

      <ResponseField name="clientSessionCachingEnabled" type="Bool" post={["Default: false"]}>
        <Warning>
          Before enabling the flag to true it's recommended to reach out to Primer
          support for additional verification since there are edge cases where it's not
          advised.
        </Warning>

        Indicates whether client session caching is enabled.

        When set to `true`, responses from the server will be cached on the client side, allowing for faster subsequent
        access to the same data within the cache duration. When set to `false`, every request to the server will be
        processed without utilizing any client-side cache, ensuring that the client always receives the most up-to-date data.
      </ResponseField>

      <ResponseField name="apiVersion" type="PrimerApiVersion" post={["Default: PrimerApiVersion.V2_4"]}>
        Indicates the API version to use when interacting with the Primer backend. Options are:

        * `PrimerApiVersion.V2_4` - will use ApiVersion 2.4

        Note that this is optional, if a value is not supplied, ApiVersion `V2.4` will be used by default.
      </ResponseField>
    </Expandable>
  </ResponseField>

  <ResponseField name="delegate" type="PrimerDelegate" post={["Optional"]}>
    Set Primer SDK's delegate and implement the required delegate methods. Alternatively you can set the delegate directly like `Primer.shared.delegate = yourDelegate`.
  </ResponseField>
</Expandable>

## Example

Configuring Primer SDK.

```swift SWIFT theme={"dark"}
// 👇 Add this
import PrimerSDK

class MyViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        // 👇 Create your settings
        let settings = PrimerSettings(
            paymentHandling: .auto,
            localeData: PrimerLocaleData(
                languageCode: "en",
                regionCode: "US"),
            paymentMethodOptions: PrimerPaymentMethodOptions(
                urlScheme: "URL_SCHEME://",
                applePayOptions: PrimerApplePayOptions(
                    merchantIdentifier: "MERCHANT_IDENTIFIER",
                    merchantName: "MERCHANT_NAME",
                    isCaptureBillingAddressEnabled: true,
                    showApplePayForUnsupportedDevice: true,
                    checkProvidedNetworks: true,
                    shippingOptions: PrimerApplePayOptions.ShippingOptions(
                        shippingContactFields: [.name, .emailAddress],
                        requireShippingMethod: true
                    ),
                    billingOptions: PrimerApplePayOptions.BillingOptions(
                        requiredBillingContactFields: [.postalAddress]
                    )
                ),
                klarnaOptions: PrimerKlarnaOptions(
                    recurringPaymentDescription: "RECURRING_PAYMENT_DESCRIPTION"),
                stripeOptions: PrimerStripeOptions(
                    publishableKey: "STRIPE_PUBLISHABLE_KEY")),
            uiOptions: PrimerUIOptions(
                isInitScreenEnabled: true,
                isSuccessScreenEnabled: true,
                isErrorScreenEnabled: true,
                cardFormUIOptions: PrimerCardFormUIOptions(
                    payButtonAddNewCard: true
                )
            ),
            debugOptions: PrimerDebugOptions(is3DSSanityCheckEnabled: false))
    }
}
```