Build a discounts user interface

In this tutorial, you'll learn how to do the following tasks:

• Add a server endpoint to your node app that creates the function owner.
• Create an App Bridge UI that enables users to create the function owner.
• Configure the UI paths for your function.

• You've completed the Add configuration to your discounts experience tutorial.

You can't invoke the GraphQL Admin API directly from your app frontend, so you must first create an API layer for the app to invoke.

1. In web/index.js, add an import for GraphqlQueryError under the existing import statements. This is helpful when trapping errors from the node GraphQL client.

2. Still in web/index.js, define the mutations that you'll need to create discounts directly after the module imports:

3. Still in web/index.js, add the following code directly after app.use(express.json()):

4. Still in web/index.js, add the endpoints directly after const app = express();:

The following example builds a React-based page that enables app users to create and configure a new discount. The Shopify node app template uses file-based routing, so the file path of the page determines its URL.

1. Navigate to the web/frontend directory.

2. Install the following packages:

   • @shopify/discount-app-components to render a discounts UI
   • @shopify/react-form to make managing your forms easier
   • @shopify/react-i18n for localization support

3. In the web/frontend/components/providers folder, create a DiscountProvider.jsx file and add a DiscountProvider component:

4. In web/frontend/components/providers/index.js, export DiscountProvider:

5. In web/frontend/App.jsx, import and render DiscountProvider.

   Your App.jsx should look similar to the following example:

6. Under web/frontend/pages, create a new folder called volume. This folder name isn't important, but it determines the URL that you configure later in Step 5.

7. Under volume, create a new folder called [functionId]. The square brackets ([]) indicate that this is a route parameter, which you can access in your frontend through the useParams hook.

8. Create a new file in [functionId] called new.jsx with the following code:

   You now have a frontend page in your app that can invoke your app backend to create a discount.

So far, this UI renders the common input fields for a discount. You must add additional fields to collect the volume discount configuration that will be stored in your metafield.

1. In web/frontend/pages/volume/[functionId]/new.jsx, populate the quantity and percentage configuration properties and define initial states for your form data:

2. In web/frontend/pages/volume/[functionId]/new.jsx, parse the quantity and percentage configuration properties and add them to your discount configuration.

   You can store your configuration in one or more metafields on a discount. Learn more about using metafields with input queries.

   The following example stores configuration in a JSON metafield:

3. In web/frontend/pages/Volume/[functionId]/new.jsx, after the MethodCard component, add a Card component for the Volume discount configuration:

In the previous tutorial, you used a metafield namespace that was accessible to any app, so that the metafield namespace could be populated using GraphiQL. To make your function ready for production, you should update the metafield namespace to use a reserved prefix so that other apps can't use your metafield.

Replace the code in the extensions/product-discount/input.graphql file with the following code:

Settings in the shopify.function.extension.toml file define the URLs that Shopify uses for enabling users to create and edit discounts based on your function. Shopify automatically fills in any dynamic tokens in these URLs.

1. In extensions/product-discount/shopify.function.extension.toml, populate the two settings directly under [ui.paths].

2. To update this setting and your input query, deploy your app and function by running the following command from your app root folder:

   A message from the CLI displays and indicates that your product-discount function is live.

1. If your app isn't already running, then start it using Shopify CLI.

2. From your Shopify admin, go to Discounts.

3. If you have existing discounts from previous tutorials, then click the checkbox next to each of them, and then click Deactivate discounts.

4. Click the Create discount button.

5. Click the product-discount discount type that you created under your app name. You should see the create page for your Volume discount.

6. Fill in values for the discount:

   • For Method, use Automatic.
   • For Title, use Volume.
   • For Minimum quantity, use 4.
   • For Discount percentage, use 20.

7. Click Save. You should see a new discount in the discounts list.

8. Open your development store and build a cart with a single item in it.

   No discounts should be applied to the cart.

9. Increase the item quantity to four.

   The 20% Volume discount should now be applied to the cart.

10. To debug your function, or view its output, you can review its logs in your Partner Dashboard:

    1. Log in to your Partner Dashboard and navigate to Apps > {your app} > Extensions > product-discount.
    2. Click on any function run to view its input, output, and any logs written to STDERR.

• Learn more about how Shopify Functions work and the benefits of using Shopify Functions.
• Consult the API references for Shopify Functions.
• Review the UX guidelines to learn how to implement discounts in user interfaces.