---
title: Build a discounts UI with React Router
description: Create a UI that merchants can use to configure your discount function.
source_url:
  html: >-
    https://shopify.dev/docs/apps/build/discounts/build-ui-with-react-router?extension=javascript
  md: >-
    https://shopify.dev/docs/apps/build/discounts/build-ui-with-react-router.md?extension=javascript
---

# Build a discounts UI with React Router

To build a UI that merchants can use to configure a Discount Function, you can use admin UI extensions to display a form on the discount details page, or you can add a page to a React Router app. This tutorial describes how to add a page to a React Router app, which will render the Discount Function editing UI at a path of your own specification.

## What you'll learn

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

1. **Scaffold a React Router app with the Shopify CLI**

   Build your app using the provided template with all necessary components.

2. **Review frontend UI components**

   Explore the app structure, including routes, forms, and Polaris components that create the merchant interface for discount configuration.

3. **Set up a discount Function**

   Configure the discount function to handle product, order, and shipping discounts using metafields and GraphQL operations.

4. **Deploy the app to Shopify**

   Push your app to Shopify and install it in your dev store.

5. **Configure a test discount**

   Using your app's interface, create an automatic discount with specific percentages for products, orders, and shipping.

6. **Verify the discount functionality**

   Test the discount in your dev store's cart and checkout flow, confirming all discount types apply correctly.

![The UI for configuring the discount](https://shopify.dev/assets/assets/apps/discounts/discount-function-order-product-shipping-wFP7iSsc.png)

## Requirements

[Create a Partner account](https://www.shopify.com/partners)

[Create a dev store](https://shopify.dev/docs/apps/tools/development-stores#create-a-development-store-to-test-your-app)

[Install Node.js](https://nodejs.org/en/download)

Install Node.js 22 or higher.

## Project

[View on GitHub](https://github.com/Shopify/discounts-reference-app/blob/main/examples/react-router-app)

## Scaffold the React Router app

To scaffold a complete React Router app, run this command to set up your development environment with a fully functional React Router app.

## Terminal

```terminal
shopify app init --template https://github.com/Shopify/discounts-reference-app/examples/react-router-app
```

This command sets up your development environment with a fully functional React Router app. The next steps walk you through the key components.

## Understand the discount configuration UI

The app structure includes these key directories.

* 📁 `components/` Reusable UI components
* 📁 `graphql/` GraphQL queries and mutations for functions, collections, and discounts
* 📁 `hooks/` Custom React hooks, including `useDiscountForm` for discount management
* 📁 `routes/` React Router routes handling app navigation, authentication, and discount management
* 📁 `types/` TypeScript definitions including form types, admin types, and generated types
* 📁 `utils/` Utility functions including navigation helpers

**Info:**

The app integrates [@shopify/polaris](https://www.npmjs.com/package/@shopify/polaris) components to match the Shopify admin interface.

## Review routes, UI components, and discount configuration

The route files manage discount creation and editing.

### Ensure the correct access scopes are set

Review the `shopify.app.toml` file to ensure the correct access scopes are set. Your app needs `write_discounts` and `read_products` scopes.

## shopify.app.toml

```toml
# This file stores configurations for your Shopify app.


scopes = "write_discounts,read_products"
[webhooks]
api_version = "2024-10"


  # Handled by: /app/routes/webhooks.app.uninstalled.tsx
  [[webhooks.subscriptions]]
  uri = "/webhooks/app/uninstalled"
  topics = ["app/uninstalled"]


  # Handled by: /app/routes/webhooks.app.scopes_update.tsx
  [[webhooks.subscriptions]]
  topics = [ "app/scopes_update" ]
  uri = "/webhooks/app/scopes_update"


  # Webhooks can have filters
  # Only receive webhooks for product updates with a product price >= 10.00
  # See: https://shopify.dev/docs/apps/build/webhooks/customize/filters
  # [[webhooks.subscriptions]]
  # topics = ["products/update"]
  # uri = "/webhooks/products/update"
  # filter = "variants.price:>=10.00"


  # Mandatory compliance topic for public apps only
  # See: https://shopify.dev/docs/apps/build/privacy-law-compliance
  # [[webhooks.subscriptions]]
  # uri = "/webhooks/customers/data_request"
  # compliance_topics = ["customers/data_request"]


  # [[webhooks.subscriptions]]
  # uri = "/webhooks/customers/redact"
  # compliance_topics = ["customers/redact"]


  # [[webhooks.subscriptions]]
  # uri = "/webhooks/shop/redact"
  # compliance_topics = ["shop/redact"]
```

### Explore the create discount route

Review the discount creation logic in the create route file.

The [`action`](https://reactrouter.com/start/framework/actions) function processes form submissions through the [`discountCodeAppCreate`](https://shopify.dev/docs/api/admin-graphql/latest/mutations/discountCodeAppCreate) mutation.

### Examine the edit discount route

To understand discount editing, review the edit route file.

### Review the `DiscountForm` component

The DiscountForm component is responsible for rendering the form that allows merchants to configure the discount:

This form includes fields required by the discount creation mutation:

* `title`
* `method`
* `code`
* `combinesWith`
* `discountClasses`
* `usageLimit`
* `appliesOncePerCustomer`
* `startsAt`
* `endsAt`
* `metafield`

### Understand the `discountClasses` configuration

The form includes a section for selecting discount classes. This section allows merchants to apply discounts to `PRODUCT`, `ORDER`, and `SHIPPING` classes.

## app/components/DiscountForm/DiscountForm.tsx

```tsx
import { returnToDiscounts } from "app/utils/navigation";
import { useCallback, useMemo, useState } from "react";
import { Form } from "react-router";


import { useDiscountForm } from "../../hooks/useDiscountForm";
import { DiscountClass } from "../../types/admin.types.d";
import { DiscountMethod } from "../../types/types";
import { CollectionPicker } from "../CollectionPicker/CollectionPicker";
import { DatePickerField } from "../DatePickerField/DatePickerField";


interface SubmitError {
  message: string;
  field: string[];
}


interface DiscountFormProps {
  initialData?: {
    title: string;
    method: DiscountMethod;
    code: string;
    combinesWith: {
      orderDiscounts: boolean;
      productDiscounts: boolean;
      shippingDiscounts: boolean;
    };
    discountClasses: DiscountClass[];
    usageLimit: number | null;
    appliesOncePerCustomer: boolean;
    startsAt: string | Date;
    endsAt: string | Date | null;
    configuration: {
      cartLinePercentage: string;
      orderPercentage: string;
      deliveryPercentage: string;
      metafieldId?: string;
      collectionIds?: string[];
```

### Review the discount percentage configuration

Examine how merchants set discount percentages.

This section of the form allows merchants to set the discount percentage for each class, using a number input.

## app/components/DiscountForm/DiscountForm.tsx

```tsx
import { returnToDiscounts } from "app/utils/navigation";
import { useCallback, useMemo, useState } from "react";
import { Form } from "react-router";


import { useDiscountForm } from "../../hooks/useDiscountForm";
import { DiscountClass } from "../../types/admin.types.d";
import { DiscountMethod } from "../../types/types";
import { CollectionPicker } from "../CollectionPicker/CollectionPicker";
import { DatePickerField } from "../DatePickerField/DatePickerField";


interface SubmitError {
  message: string;
  field: string[];
}


interface DiscountFormProps {
  initialData?: {
    title: string;
    method: DiscountMethod;
    code: string;
    combinesWith: {
      orderDiscounts: boolean;
      productDiscounts: boolean;
      shippingDiscounts: boolean;
    };
    discountClasses: DiscountClass[];
    usageLimit: number | null;
    appliesOncePerCustomer: boolean;
    startsAt: string | Date;
    endsAt: string | Date | null;
    configuration: {
      cartLinePercentage: string;
      orderPercentage: string;
      deliveryPercentage: string;
      metafieldId?: string;
      collectionIds?: string[];
```

### Explore the `CollectionPicker` component

Review how collection selection works.

This section uses the AppBridge `ResourcePicker` component to allow merchants to select collections, to make sure that discounts are applied to the expected products.

**Tip:**

The discount configuration uses metafields for storage. Learn more about [using metafields with input queries](https://shopify.dev/docs/apps/build/functions/input-queries/metafields-for-input-queries).

## Review server-side discount management

To learn how the React Router app handles server-side operations, examine the files in the app/models directory. These files query and mutate resources using Shopify's GraphQL Admin API.

### Explore functions server file

This file queries the Functions associated with your app. We use this query to populate the `functionId` field used in the `discountAutomaticAppCreate` and `discountCodeAppCreate` mutations.

### Review collections server file

This file handles collection data stored in discount metafields. We use this query to populate the list of collections displayed in the section where merchants can select collections to target with the discount. When editing a discount, we use this query to populate the list of collections displayed below the resource picker.

### Examine discounts server file

This file manages discount creation, updates, and retrieval. We use this file to create, read, and update discounts.

## Review Graph​QL operations

In this step, you'll examine the app's GraphQL queries and mutations. These operations communicate with the Shopify Admin GraphQL API to create, read, and update discounts, retrieve collections, and retrieve functions.

### Review discount graphql file

These queries and mutations handle, retrieving discounts, creating code and automatic discounts, and updating code and automatic discounts.

### Examine collections graphql file

This file contains queries for collection data which is used to populate the list of collections displayed in the section where merchants can select collections. When editing a discount, we use this query to populate the list of collections displayed below the resource picker.

### Review functions graphql file

This query returns functions for your app when the app is installed on a merchant's store. This example uses this query to populate the app's home page, which allows you to navigate to the create discount page and it also populates the `functionId` field used in the `discountAutomaticAppCreate` and `discountCodeAppCreate` mutations.

## Set up the Discount Function

Now, create a Discount Function. This function will be used to apply discounts to products, orders, and shipping, and merchants can configure these discounts using your React Router app's UI.

Run this command to scaffold your Discount Function:

## Terminal

```terminal
shopify app generate extension --template discount --name discount-function-js
```

## Configure the Discount Function

In this step, you'll configure the Discount Function to apply discounts to products, orders, and shipping based on the discount configuration that is stored on the discount instance and its metafield.

**Caution:**

Your Function should only return operations for `discountClasses` that the discount applies to. For example, if the discount is configured to apply to `PRODUCT` and `ORDER`, but not `SHIPPING`, your Function should only return operations for `PRODUCT` and `ORDER`.

### Define the UI paths and input variables

1. Update the UI paths in `shopify.extension.toml`. This property tells the Shopify admin where to find the UI that allows merchants to configure discounts associated with your Discount Function.
2. Register a metafield variable that your Function will use as a dynamic input. Refer to [variables in input queries](https://shopify.dev/docs/apps/build/functions/input-queries/use-variables-input-queries) for more information. In this example, the `collectionIds` property of the metafield object is used as the input variable for the Function.

## extensions/shopify.extension.toml

```toml
api_version = "2025-04"


[[extensions]]
name = "t:name"
description = "t:description"
handle = "discount-function-rs"
type = "function"


  [[extensions.targeting]]
  target = "cart.lines.discounts.generate.run"
  input_query = "src/generate_cart_run.graphql"
  export = "generate-cart-run"


  [[extensions.targeting]]
  target = "cart.delivery-options.discounts.generate.run"
  input_query = "src/generate_delivery_run.graphql"
  export = "generate-delivery-run"


  [extensions.build]
  command = ""
  path = "dist/function.wasm"


[extensions.input.variables]
namespace = "$app:example-discounts--ui-extension"
key = "function-configuration"


[extensions.ui]
handle = "ui-multiclass-metafield-js"


[extensions.ui.paths]
create = "/app/discount/:functionId/new"
details = "/app/discount/:functionId/:id"
```

### Query the data needed for your Function cart run target

The `cart_lines_discounts_generate_run.graphql` file drives your function logic by querying essential cart data which is used as the input for your Function. This file queries:

* Cart properties to use with the `inAnyCollection` field for determining which collections your Function will target, `$collectionIds` are passed to the query as a variable.
* The `discountClasses` property to identify which discount classes (PRODUCT, ORDER, SHIPPING) your Function will return discounts for.
* Metafield data to retrieve collection IDs and discount percentage values. The metafield is queried by its key and namespace.

**Tip:**

The [`inAnyCollection`](https://shopify.dev/docs/api/functions/reference/discount/graphql/common-objects/product) field is used to determine whether a product belongs to one of the specified collections. This field is `true` when a product variant is associated with the specified set of collections, and `false` otherwise. Note that if the collection set is empty, it returns `false`.

## extensions/discount-function/src/cart\_lines\_discounts\_generate\_run.graphql

```graphql
query CartInput($collectionIds: [ID!]) {
  cart {
    lines {
      id
      cost {
        subtotalAmount {
          amount
        }
      }
      merchandise {
        __typename
        ... on ProductVariant {
          product {
            inAnyCollection(ids: $collectionIds)
          }
        }
      }
    }
  }
  discount {
    discountClasses
    metafield(namespace: "$app", key: "function-configuration") {
      value
    }
  }
}
```

### Query the data needed for your Function delivery run target

The `cart_delivery_options_discounts_generate_run.graphql` file drives your function logic by querying essential delivery data which is used as the input for your Function. This file queries:

* Cart `deliveryGroups` to retrieve the delivery options available to the customer.
* The `discountClasses` property to determine whether the SHIPPING discount class is set.
* Metafield data to retrieve the discount percentage for delivery options. The metafield is queried by its key and namespace.

**Note:**

Checkouts and orders can include multiple delivery methods, such as shipping and pickup in the same order. When your app uses delivery or fulfillment data, iterate over all delivery groups or fulfillment orders to determine the delivery method for each one. Don't assume one method for the order. For more information, refer to [split carts in checkout](https://shopify.dev/docs/apps/build/orders-fulfillment/split-carts).

## extensions/discount-function/src/cart\_delivery\_options\_discounts\_generate\_run.graphql

```graphql
query DeliveryInput {
  cart {
    deliveryGroups {
      id
    }
  }
  discount {
    discountClasses
    metafield(namespace: "$app", key: "function-configuration") {
      value
    }
  }
}
```

### Create your cart run Function logic

Using the input data from the `cart_lines_discounts_generate_run.graphql` file, you can create your Function's logic.

In this example, you retrieve the metafield object which contains the cart line and order discount percentages, the collection IDs for which the discount applies and the discountClasses that your discount will apply to. You can then use this data to create your Function's logic.

First, you parse the metafield, then you can conditionally add [ProductDiscountsAddOperation](https://shopify.dev/docs/api/functions/reference/discount/graphql/common-objects/productdiscountsaddoperation) and [OrderDiscountsAddOperation](https://shopify.dev/docs/api/functions/reference/discount/graphql/common-objects/orderdiscountsaddoperation) operations to the return value based on whether the cart line's product is part of a collection that your discount targets, and whether the discountClasses for the discount are set to `PRODUCT` or `ORDER`.

## extensions/discount-function/src/cart\_lines\_discounts\_generate\_run.js

```javascript
import {
  OrderDiscountSelectionStrategy,
  ProductDiscountSelectionStrategy,
  DiscountClass,
} from "../generated/api";


export function cartLinesDiscountsGenerateRun(input) {
  if (!input.cart.lines.length) {
    throw new Error("No cart lines found");
  }


  const { cartLinePercentage, orderPercentage, collectionIds } = parseMetafield(
    input.discount.metafield,
  );


  const hasOrderDiscountClass = input.discount.discountClasses.includes(
    DiscountClass.Order,
  );
  const hasProductDiscountClass = input.discount.discountClasses.includes(
    DiscountClass.Product,
  );


  if (!hasOrderDiscountClass && !hasProductDiscountClass) {
    return { operations: [] };
  }


  const operations = [];
  // Add product discounts first if available and allowed
  if (hasProductDiscountClass && cartLinePercentage > 0) {
    const cartLineTargets = input.cart.lines.reduce((targets, line) => {
      if (
        "product" in line.merchandise &&
        (line.merchandise.product.inAnyCollection || collectionIds.length === 0)
      ) {
        targets.push({
          cartLine: {
            id: line.id,
          },
        });
      }
      return targets;
    }, []);


    if (cartLineTargets.length > 0) {
      operations.push({
        productDiscountsAdd: {
          candidates: [
            {
              message: `${cartLinePercentage}% OFF PRODUCT`,
              targets: cartLineTargets,
              value: {
                percentage: {
                  value: cartLinePercentage,
                },
              },
            },
          ],
          selectionStrategy: ProductDiscountSelectionStrategy.First,
        },
      });
    }
  }


  // Then add order discounts if available and allowed
  if (hasOrderDiscountClass && orderPercentage > 0) {
    operations.push({
      orderDiscountsAdd: {
        candidates: [
          {
            message: `${orderPercentage}% OFF ORDER`,
            targets: [
              {
                orderSubtotal: {
                  excludedCartLineIds: [],
                },
              },
            ],
            value: {
              percentage: {
                value: orderPercentage,
              },
            },
          },
        ],
        selectionStrategy: OrderDiscountSelectionStrategy.First,
      },
    });
  }


  return { operations };
}


function parseMetafield(metafield) {
  try {
    const value = JSON.parse(metafield.value);
    return {
      cartLinePercentage: value.cartLinePercentage || 0,
      orderPercentage: value.orderPercentage || 0,
      collectionIds: value.collectionIds || [],
    };
  } catch (error) {
    console.error("Error parsing metafield", error);
    return {
      cartLinePercentage: 0,
      orderPercentage: 0,
      collectionIds: [],
    };
  }
}
```

### Create your delivery run Function logic

Using the input data from the `cart_delivery_options_discounts_generate_run.graphql` file, you can create your Function's logic.

In this example, you retrieve the metafield object which contains the delivery discount percentage. You can then use this data to create your Function's logic.

First, you parse the metafield, then you can conditionally add [DeliveryDiscountsAddOperation](https://shopify.dev/docs/api/functions/reference/discount/graphql/common-objects/deliverydiscountsaddoperation) operations to the return value based on whether the discountClasses for the discount are set to `SHIPPING`.

## extensions/discount-function/src/cart\_delivery\_options\_discounts\_generate\_run.js

```javascript
import {
  DeliveryDiscountSelectionStrategy,
  DiscountClass,
} from "../generated/api";


export function cartDeliveryOptionsDiscountsGenerateRun(input) {
  const firstDeliveryGroup = input.cart.deliveryGroups[0];
  if (!firstDeliveryGroup) {
    throw new Error("No delivery groups found");
  }


  const { deliveryPercentage } = parseMetafield(input.discount.metafield);
  const hasShippingDiscountClass = input.discount.discountClasses.includes(
    DiscountClass.Shipping,
  );
  if (!hasShippingDiscountClass) {
    return { operations: [] };
  }


  const operations = [];
  if (hasShippingDiscountClass && deliveryPercentage > 0) {
    operations.push({
      deliveryDiscountsAdd: {
        candidates: [
          {
            message: `${deliveryPercentage}% OFF DELIVERY`,
            targets: [
              {
                deliveryGroup: {
                  id: firstDeliveryGroup.id,
                },
              },
            ],
            value: {
              percentage: {
                value: deliveryPercentage,
              },
            },
          },
        ],
        selectionStrategy: DeliveryDiscountSelectionStrategy.All,
      },
    });
  }
  return { operations };
}


function parseMetafield(metafield) {
  try {
    const value = JSON.parse(metafield.value);
    return { deliveryPercentage: value.deliveryPercentage || 0 };
  } catch (error) {
    console.error("Error parsing metafield", error);
    return { deliveryPercentage: 0 };
  }
}
```

## Deploy your app

When you're ready to release your changes to users, you can create and release an [app version](https://shopify.dev/docs/apps/launch/deployment/app-versions). An app version is a snapshot of your app configuration and all extensions.

1. Navigate to your app directory.

2. Run the following command.

   Optionally, you can provide a name or message for the version using the `--version` and `--message` flags.

   ## Terminal

   ```terminal
   shopify app deploy
   ```

Releasing an app version replaces the current active version that's served to stores that have your app installed. It might take several minutes for app users to be upgraded to the new version.

**Tip:**

If you want to create a version, but avoid releasing it to users, then run the `deploy` command with a `--no-release` flag. You can release the unreleased app version using Shopify CLI's [`release`](https://shopify.dev/docs/api/shopify-cli/app/app-release) command, or through the Dev Dashboard.

## Create a test discount

1. In your Shopify admin, navigate to **Discounts**.

2. To prevent conflicting discounts from activating, deactivate any existing discounts.

3. Click **Create discount**.

4. Under your app name, select your discount function.

5. Configure the discount with these values:

   * **Method**: **Automatic**
   * **Title**: **Product, Order, Shipping Discount**
   * **DiscountClasses**: Select **Product**, **Order**, and **Shipping**
   * **Product discount percentage**: **20**
   * **Order discount percentage**: **10**
   * **Shipping discount percentage**: **5**
   * **Collection IDs**: Select your test collections

6. Click **Save**

## Test the discount

1. Open **Discounts** in your Shopify admin
2. Locate your new cart line, order, and shipping discount

   ![A list of all active discounts for the store.](https://shopify.dev/assets/assets/apps/discounts/functions-discount-list-multi-class-bMqqn_8b.png)
3. Now, go to your dev store and add products to your cart.

Your cart page displays:

* Product line discounts
* Order subtotal discount

Your checkout page displays:

* Product line discounts
* Order subtotal discount
* Shipping rate discounts (after entering shipping address)

  ![A checkout summary that lists discounts for all three classes](https://shopify.dev/assets/assets/apps/discounts/multi-class-DqNqJQCF.png)

### Review the execution of the Function

### Review the Function execution

1. In the terminal where `shopify app dev` is running, review your Function executions.

   When [testing Functions on development stores](https://shopify.dev/docs/apps/build/functions/test-debug-functions#test-your-function-on-a-development-store), the `dev` output shows Function executions, debug logs you've added, and a link to a local file containing full execution details.

2. In a new terminal window, use the Shopify CLI command [`app function replay`](https://shopify.dev/docs/api/shopify-cli/app/app-function-replay) to [replay a Function execution locally](https://shopify.dev/docs/apps/build/functions/test-debug-functions#execute-the-function-locally-using-shopify-cli). This lets you debug your Function without triggering it again on Shopify.

   ## Terminal

   ```terminal
   shopify app function replay
   ```

3. Select the Function execution from the top of the list. Press `q` to quit when you are finished debugging.

## shopify.app.toml

```toml
# This file stores configurations for your Shopify app.


scopes = "write_discounts,read_products"
[webhooks]
api_version = "2024-10"


  # Handled by: /app/routes/webhooks.app.uninstalled.tsx
  [[webhooks.subscriptions]]
  uri = "/webhooks/app/uninstalled"
  topics = ["app/uninstalled"]


  # Handled by: /app/routes/webhooks.app.scopes_update.tsx
  [[webhooks.subscriptions]]
  topics = [ "app/scopes_update" ]
  uri = "/webhooks/app/scopes_update"


  # Webhooks can have filters
  # Only receive webhooks for product updates with a product price >= 10.00
  # See: https://shopify.dev/docs/apps/build/webhooks/customize/filters
  # [[webhooks.subscriptions]]
  # topics = ["products/update"]
  # uri = "/webhooks/products/update"
  # filter = "variants.price:>=10.00"


  # Mandatory compliance topic for public apps only
  # See: https://shopify.dev/docs/apps/build/privacy-law-compliance
  # [[webhooks.subscriptions]]
  # uri = "/webhooks/customers/data_request"
  # compliance_topics = ["customers/data_request"]


  # [[webhooks.subscriptions]]
  # uri = "/webhooks/customers/redact"
  # compliance_topics = ["customers/redact"]


  # [[webhooks.subscriptions]]
  # uri = "/webhooks/shop/redact"
  # compliance_topics = ["shop/redact"]
```

## app/routes/app.discount.$functionId.new\.tsx

```tsx
import {
  type ActionFunctionArgs,
  useActionData,
  useLoaderData,
  useNavigation,
} from "react-router";


import { DiscountForm } from "../components/DiscountForm/DiscountForm";
import {
  createCodeDiscount,
  createAutomaticDiscount,
} from "../models/discounts.server";
import { DiscountMethod } from "../types/types";
import { returnToDiscounts } from "../utils/navigation";


export const loader = async () => {
  // Initially load with empty collections since none are selected yet
  return { collections: [] };
};


export const action = async ({ params, request }: ActionFunctionArgs) => {
  const { functionId } = params;
  const formData = await request.formData();
  const discountData = formData.get("discount");
  if (!discountData || typeof discountData !== "string")
    throw new Error("No discount data provided");


  const {
    title,
    method,
    code,
    combinesWith,
    usageLimit,
    appliesOncePerCustomer,
    startsAt,
    endsAt,
```

## app/routes/app.discount.$functionId.$id.tsx

```tsx
import { Collection, DiscountClass } from "app/types/admin.types";
import {
  type ActionFunctionArgs,
  type LoaderFunctionArgs,
  useActionData,
  useLoaderData,
  useNavigation,
} from "react-router";


import { DiscountForm } from "../components/DiscountForm/DiscountForm";
import { NotFoundPage } from "../components/NotFoundPage";
import { getCollectionsByIds } from "../models/collections.server";
import {
  getDiscount,
  updateAutomaticDiscount,
  updateCodeDiscount,
} from "../models/discounts.server";
import { DiscountMethod } from "../types/types";


interface ActionData {
  errors?: {
    code?: string;
    message: string;
    field?: string[];
  }[];
  success?: boolean;
}


interface LoaderData {
  discount: {
    title: string;
    method: DiscountMethod;
    code: string;
    combinesWith: {
      orderDiscounts: boolean;
      productDiscounts: boolean;
```

## app/components/DiscountForm/DiscountForm.tsx

```tsx
import { returnToDiscounts } from "app/utils/navigation";
import { useCallback, useMemo, useState } from "react";
import { Form } from "react-router";


import { useDiscountForm } from "../../hooks/useDiscountForm";
import { DiscountClass } from "../../types/admin.types.d";
import { DiscountMethod } from "../../types/types";
import { CollectionPicker } from "../CollectionPicker/CollectionPicker";
import { DatePickerField } from "../DatePickerField/DatePickerField";


interface SubmitError {
  message: string;
  field: string[];
}


interface DiscountFormProps {
  initialData?: {
    title: string;
    method: DiscountMethod;
    code: string;
    combinesWith: {
      orderDiscounts: boolean;
      productDiscounts: boolean;
      shippingDiscounts: boolean;
    };
    discountClasses: DiscountClass[];
    usageLimit: number | null;
    appliesOncePerCustomer: boolean;
    startsAt: string | Date;
    endsAt: string | Date | null;
    configuration: {
      cartLinePercentage: string;
      orderPercentage: string;
      deliveryPercentage: string;
      metafieldId?: string;
      collectionIds?: string[];
```

## app/components/CollectionPicker/CollectionPicker.tsx

```tsx
import { useCallback } from "react";


interface Collection {
  id: string;
  title: string;
}


interface ResourcePickerResponse {
  id: string;
  title: string;
}


interface CollectionPickerProps {
  onSelect: (selectedCollections: { id: string; title: string }[]) => void;
  selectedCollectionIds: string[];
  collections: Collection[];
  buttonText?: string;
}


export function CollectionPicker({
  onSelect,
  selectedCollectionIds = [],
  collections = [],
  buttonText = "Select collections",
}: CollectionPickerProps) {
  const handleSelect = useCallback(async () => {
    const selected = await window.shopify.resourcePicker({
      type: "collection",
      action: "select",
      multiple: true,
      selectionIds: selectedCollectionIds.map((id) => ({
        id: id,
        type: "collection",
      })),
    });


    if (selected) {
      const selectedCollections = selected.map(
        (collection: ResourcePickerResponse) => ({
          id: collection.id,
          title: collection.title,
        }),
      );
      onSelect(selectedCollections);
    }
  }, [selectedCollectionIds, onSelect]);


  const handleRemove = useCallback(
    (collectionId: string) => {
      onSelect(
        collections.filter((collection) => collection.id !== collectionId),
      );
    },
    [onSelect, collections],
  );


  const selectedCollectionsText = collections?.length
    ? ` (${collections.length} selected)`
    : "";


  return (
    <s-stack direction="block" gap="base">
      <s-button type="button" onClick={handleSelect}>
        {buttonText}
        {selectedCollectionsText}
      </s-button>
      {collections?.length > 0 ? (
        <s-stack direction="block" gap="small">
          {collections.map((collection) => (
            <s-stack direction="block" gap="small" key={collection.id}>
              <s-stack direction="inline" justifyContent="space-between">
                <s-link
                  href={`shopify://admin/collections/${collection.id.split("/").pop()}`}
                  target="_self"
                >
                  {collection.title}
                </s-link>
                <s-button
                  variant="tertiary"
                  type="button"
                  onClick={() => handleRemove(collection.id)}
                  aria-label={`Remove ${collection.title}`}
                >
                  <svg viewBox="0 0 20 20" width="20" height="20">
                    <path
                      d="M11.5 8.25a.75.75 0 0 1 .75.75v4.25a.75.75 0 0 1-1.5 0v-4.25a.75.75 0 0 1 .75-.75Z"
                      fill="currentColor"
                    />
                    <path
                      d="M9.25 9a.75.75 0 0 0-1.5 0v4.25a.75.75 0 0 0 1.5 0v-4.25Z"
                      fill="currentColor"
                    />
                    <path
                      fillRule="evenodd"
                      d="M7.25 5.25a2.75 2.75 0 0 1 5.5 0h3a.75.75 0 0 1 0 1.5h-.75v5.45c0 1.68 0 2.52-.327 3.162a3 3 0 0 1-1.311 1.311c-.642.327-1.482.327-3.162.327h-.4c-1.68 0-2.52 0-3.162-.327a3 3 0 0 1-1.311-1.311c-.327-.642-.327-1.482-.327-3.162v-5.45h-.75a.75.75 0 0 1 0-1.5h3Zm1.5 0a1.25 1.25 0 1 1 2.5 0h-2.5Zm-2.25 1.5h7v5.45c0 .865-.001 1.423-.036 1.848-.033.408-.09.559-.128.633a1.5 1.5 0 0 1-.655.655c-.074.038-.225.095-.633.128-.425.035-.983.036-1.848.036h-.4c-.865 0-1.423-.001-1.848-.036-.408-.033-.559-.09-.633-.128a1.5 1.5 0 0 1-.656-.655c-.037-.074-.094-.225-.127-.633-.035-.425-.036-.983-.036-1.848v-5.45Z"
                      fill="currentColor"
                    />
                  </svg>
                </s-button>
              </s-stack>
              <s-divider />
            </s-stack>
          ))}
        </s-stack>
      ) : null}
    </s-stack>
  );
}
```

## app/models/functions.server.ts

```typescript
import { GET_FUNCTIONS } from "../graphql/functions";
import { authenticate } from "../shopify.server";


export interface ShopifyFunction {
  id: string;
  title: string;
  functionType: string;
}


export async function getFunctions(request: Request) {
  const { admin } = await authenticate.admin(request);
  const response = await admin.graphql(GET_FUNCTIONS);
  const json = await response.json();
  return json.data.shopifyFunctions.nodes as ShopifyFunction[];
}
```

## app/models/collections.server.ts

```typescript
import { GET_COLLECTIONS } from "../graphql/collections";
import { authenticate } from "../shopify.server";


interface Collection {
  id: string;
  title: string;
}


export async function getCollectionsByIds(
  request: Request,
  collectionIds: string[],
) {
  const { admin } = await authenticate.admin(request);


  const response = await admin.graphql(GET_COLLECTIONS, {
    variables: {
      ids: collectionIds.map((id: string) =>
        id.includes("gid://") ? id : `gid://shopify/Collection/${id}`,
      ),
    },
  });


  const { data } = await response.json();
  return data.nodes.filter(Boolean) as Collection[];
}
```

## app/models/discounts.server.ts

```typescript
import {
  CREATE_CODE_DISCOUNT,
  CREATE_AUTOMATIC_DISCOUNT,
  UPDATE_CODE_DISCOUNT,
  UPDATE_AUTOMATIC_DISCOUNT,
  GET_DISCOUNT,
} from "../graphql/discounts";
import { authenticate } from "../shopify.server";
import type { DiscountClass } from "../types/admin.types";
import { DiscountMethod } from "../types/types";


interface BaseDiscount {
  functionId?: string;
  title: string;
  discountClasses: DiscountClass[];
  combinesWith: {
    orderDiscounts: boolean;
    productDiscounts: boolean;
    shippingDiscounts: boolean;
  };
  startsAt: Date;
  endsAt: Date | null;
}


interface DiscountConfiguration {
  cartLinePercentage: number;
  orderPercentage: number;
  deliveryPercentage: number;
  collectionIds?: string[];
}


interface UserError {
  code?: string;
  message: string;
  field?: string[];
}
```

## app/graphql/discounts.ts

```typescript
// Queries
export const GET_DISCOUNT = `
  query GetDiscount($id: ID!) {
    discountNode(id: $id) {
      id
      configurationField: metafield(
        namespace: "$app:example-discounts--ui-extension"
        key: "function-configuration"
      ) {
        id
        value
      }
      discount {
        __typename
        ... on DiscountAutomaticApp {
          title
          discountClasses
          combinesWith {
            orderDiscounts
            productDiscounts
            shippingDiscounts
          }
          startsAt
          endsAt
        }
        ... on DiscountCodeApp {
          title
          discountClasses
          combinesWith {
            orderDiscounts
            productDiscounts
            shippingDiscounts
          }
          startsAt
          endsAt
          usageLimit
          appliesOncePerCustomer
          codes(first: 1) {
            nodes {
              code
            }
          }
        }
      }
    }
  }
`;


// Mutations
export const UPDATE_CODE_DISCOUNT = `
  mutation UpdateCodeDiscount($id: ID!, $discount: DiscountCodeAppInput!) {
    discountUpdate: discountCodeAppUpdate(id: $id, codeAppDiscount: $discount) {
      userErrors {
        code
        message
        field
      }
    }
  }
`;


export const UPDATE_AUTOMATIC_DISCOUNT = `
  mutation UpdateAutomaticDiscount(
    $id: ID!
    $discount: DiscountAutomaticAppInput!
  ) {
    discountUpdate: discountAutomaticAppUpdate(
      id: $id
      automaticAppDiscount: $discount
    ) {
      userErrors {
        code
        message
        field
      }
    }
  }
`;


export const CREATE_CODE_DISCOUNT = `
  mutation CreateCodeDiscount($discount: DiscountCodeAppInput!) {
    discountCreate: discountCodeAppCreate(codeAppDiscount: $discount) {
      codeAppDiscount {
        discountId
      }
      userErrors {
        code
        message
        field
      }
    }
  }
`;


export const CREATE_AUTOMATIC_DISCOUNT = `
  mutation CreateAutomaticDiscount($discount: DiscountAutomaticAppInput!) {
    discountCreate: discountAutomaticAppCreate(
      automaticAppDiscount: $discount
    ) {
      automaticAppDiscount {
        discountId
      }
      userErrors {
        code
        message
        field
      }
    }
  }
`;
```

## app/graphql/collections.ts

```typescript
export const GET_COLLECTIONS = `
  query GetCollections($ids: [ID!]!) {
    nodes(ids: $ids) {
      ... on Collection {
        id
        title
      }
    }
  }
`;
```

## app/graphql/functions.ts

```typescript
export const GET_FUNCTIONS = `
  query GetFunctions {
    shopifyFunctions(first: 10) {
      nodes {
        id
        title
      }
    }
  }
`;
```

## extensions/shopify.extension.toml

```toml
api_version = "2025-04"


[[extensions]]
name = "t:name"
description = "t:description"
handle = "discount-function-rs"
type = "function"


  [[extensions.targeting]]
  target = "cart.lines.discounts.generate.run"
  input_query = "src/generate_cart_run.graphql"
  export = "generate-cart-run"


  [[extensions.targeting]]
  target = "cart.delivery-options.discounts.generate.run"
  input_query = "src/generate_delivery_run.graphql"
  export = "generate-delivery-run"


  [extensions.build]
  command = ""
  path = "dist/function.wasm"


[extensions.input.variables]
namespace = "$app:example-discounts--ui-extension"
key = "function-configuration"


[extensions.ui]
handle = "ui-multiclass-metafield-js"


[extensions.ui.paths]
create = "/app/discount/:functionId/new"
details = "/app/discount/:functionId/:id"
```

## extensions/discount-function/src/cart\_lines\_discounts\_generate\_run.graphql

```graphql
query CartInput($collectionIds: [ID!]) {
  cart {
    lines {
      id
      cost {
        subtotalAmount {
          amount
        }
      }
      merchandise {
        __typename
        ... on ProductVariant {
          product {
            inAnyCollection(ids: $collectionIds)
          }
        }
      }
    }
  }
  discount {
    discountClasses
    metafield(namespace: "$app", key: "function-configuration") {
      value
    }
  }
}
```

## extensions/discount-function/src/cart\_delivery\_options\_discounts\_generate\_run.graphql

```graphql
query DeliveryInput {
  cart {
    deliveryGroups {
      id
    }
  }
  discount {
    discountClasses
    metafield(namespace: "$app", key: "function-configuration") {
      value
    }
  }
}
```

## extensions/discount-function/src/cart\_lines\_discounts\_generate\_run.js

```javascript
import {
  OrderDiscountSelectionStrategy,
  ProductDiscountSelectionStrategy,
  DiscountClass,
} from "../generated/api";


export function cartLinesDiscountsGenerateRun(input) {
  if (!input.cart.lines.length) {
    throw new Error("No cart lines found");
  }


  const { cartLinePercentage, orderPercentage, collectionIds } = parseMetafield(
    input.discount.metafield,
  );


  const hasOrderDiscountClass = input.discount.discountClasses.includes(
    DiscountClass.Order,
  );
  const hasProductDiscountClass = input.discount.discountClasses.includes(
    DiscountClass.Product,
  );


  if (!hasOrderDiscountClass && !hasProductDiscountClass) {
    return { operations: [] };
  }


  const operations = [];
  // Add product discounts first if available and allowed
  if (hasProductDiscountClass && cartLinePercentage > 0) {
    const cartLineTargets = input.cart.lines.reduce((targets, line) => {
      if (
        "product" in line.merchandise &&
        (line.merchandise.product.inAnyCollection || collectionIds.length === 0)
      ) {
        targets.push({
          cartLine: {
            id: line.id,
          },
        });
      }
      return targets;
    }, []);


    if (cartLineTargets.length > 0) {
      operations.push({
        productDiscountsAdd: {
          candidates: [
            {
              message: `${cartLinePercentage}% OFF PRODUCT`,
              targets: cartLineTargets,
              value: {
                percentage: {
                  value: cartLinePercentage,
                },
              },
            },
          ],
          selectionStrategy: ProductDiscountSelectionStrategy.First,
        },
      });
    }
  }


  // Then add order discounts if available and allowed
  if (hasOrderDiscountClass && orderPercentage > 0) {
    operations.push({
      orderDiscountsAdd: {
        candidates: [
          {
            message: `${orderPercentage}% OFF ORDER`,
            targets: [
              {
                orderSubtotal: {
                  excludedCartLineIds: [],
                },
              },
            ],
            value: {
              percentage: {
                value: orderPercentage,
              },
            },
          },
        ],
        selectionStrategy: OrderDiscountSelectionStrategy.First,
      },
    });
  }


  return { operations };
}


function parseMetafield(metafield) {
  try {
    const value = JSON.parse(metafield.value);
    return {
      cartLinePercentage: value.cartLinePercentage || 0,
      orderPercentage: value.orderPercentage || 0,
      collectionIds: value.collectionIds || [],
    };
  } catch (error) {
    console.error("Error parsing metafield", error);
    return {
      cartLinePercentage: 0,
      orderPercentage: 0,
      collectionIds: [],
    };
  }
}
```

## extensions/discount-function/src/cart\_delivery\_options\_discounts\_generate\_run.js

```javascript
import {
  DeliveryDiscountSelectionStrategy,
  DiscountClass,
} from "../generated/api";


export function cartDeliveryOptionsDiscountsGenerateRun(input) {
  const firstDeliveryGroup = input.cart.deliveryGroups[0];
  if (!firstDeliveryGroup) {
    throw new Error("No delivery groups found");
  }


  const { deliveryPercentage } = parseMetafield(input.discount.metafield);
  const hasShippingDiscountClass = input.discount.discountClasses.includes(
    DiscountClass.Shipping,
  );
  if (!hasShippingDiscountClass) {
    return { operations: [] };
  }


  const operations = [];
  if (hasShippingDiscountClass && deliveryPercentage > 0) {
    operations.push({
      deliveryDiscountsAdd: {
        candidates: [
          {
            message: `${deliveryPercentage}% OFF DELIVERY`,
            targets: [
              {
                deliveryGroup: {
                  id: firstDeliveryGroup.id,
                },
              },
            ],
            value: {
              percentage: {
                value: deliveryPercentage,
              },
            },
          },
        ],
        selectionStrategy: DeliveryDiscountSelectionStrategy.All,
      },
    });
  }
  return { operations };
}


function parseMetafield(metafield) {
  try {
    const value = JSON.parse(metafield.value);
    return { deliveryPercentage: value.deliveryPercentage || 0 };
  } catch (error) {
    console.error("Error parsing metafield", error);
    return { deliveryPercentage: 0 };
  }
}
```

## Tutorial complete!

You've successfully created a Discount Function and React Router app that allows merchants to set the discounts applied by that Function. Now, you can use this Function to apply discounts that target cart lines, order subtotals, and shipping rates.

***

### Next Steps

[Add network access to your discount Function\
\
Learn how to add network access to your discount Function to query an external system for discount code validation.](https://shopify.dev/docs/apps/build/discounts/network-access)[Review the UX guidelines\
\
Review the UX guidelines to learn how to implement discounts in user interfaces.](https://shopify.dev/docs/apps/build/discounts/ux-for-discounts)[Learn more about Shopify Functions\
\
Learn more about how Shopify Functions work and the benefits of using Shopify Functions.](https://shopify.dev/docs/apps/build/functions)[Consult the Shopify Functions API references\
\
Consult the API references for Shopify Functions](https://shopify.dev/docs/api/functions)[Learn more about deploying app versions\
\
Learn more about deploying app versions to Shopify](https://shopify.dev/docs/apps/launch/deployment/deploy-app-versions)