# Using APIs

Once you have defined your APIs, you can connect them to your UI. In Digia, there are three primary ways to use an API depending on your needs.

## 1. FutureBuilder (Load on Render)

The [**FutureBuilder**](https://docs.digia.tech/ui-building-blocks/widgets/media-async-widgets/future-builder) widget is used to fetch data as soon as a widget is rendered on the screen.

### Best For

* **Page Load**: Fetching data when the user lands on a screen (e.g., getting User Profile on the Profile Page).
* **Widget Load**: Loading async data for a specific section (e.g., a "Trending Now" section on the Home Page).

### How to use

1. Drag a `FutureBuilder` widget onto your canvas.
2. In the properties panel, select the **API Call** you want to run.
3. **Bind Arguments**: If your API needs parameters (like `userId`), bind them to variables (e.g., `PageParams`).
4. **Handle States**: To manage different API states (Loading, Success, Failure), you can use a [**ConditionalBuilder**](https://docs.digia.tech/ui-building-blocks/widgets/layout-structure-widgets/conditional-builder) widget.
   * **Loading**: Show a Spinner or Skeleton loader.
   * **Success**: Show the actual content (access data via `apiResponse`).
   * **Error**: Show an Error message or Retry button.

## 2. Paginated List View (Infinite Scroll)

For lists that contain too much data to fetch at once (like a Social Feed or Product Catalog), use the [**PaginatedListView**](https://docs.digia.tech/ui-building-blocks/widgets/scrolling-widgets/paginated-listview).

### Best For

* Long lists where you need "Load More" functionality as the user scrolls.

### How to use

The widget handles the complexity of "page numbers" and "offsets" for you.

1. Select the `PaginatedListView` widget.
2. Bind it to an API that supports pagination (accepts `page` or `offset/limit` params).
3. Digia automatically calls the API for the next page when the user scrolls to the bottom.

## 3. Call REST API Action (Event Driven)

Use the [**Call Rest API Action**](https://docs.digia.tech/logic-and-interaction/actions/call-rest-api) when you need complete control over *when* the API is called.

### Best For

* **Button Clicks**: "Submit Form", "Login", "Add to Cart".
* **Fire & Forget**: Sending analytics or logs where you don't need to show the result immediately.
* **Chain Reactions**: Calling an API after a form validation succeeds.

### How to use

1. Select an interactive widget (like a Button).
2. Add an Action: **Call Rest API**.
3. Select which API to call.
4. **Handle Response**:
   * **On Success**: Store the result in a Variable (App/Page State) or Navigate to another page.
   * **On Failure**: Show a [Toast](https://docs.digia.tech/logic-and-interaction/actions/toast) or error dialog.