Object Generation with useObject

Learn how to generate and stream structured JSON objects with the useObject hook for type-safe data streaming.

Object Generation

useObject is an experimental feature and only available in React, Svelte, and Vue.

The useObject hook allows you to create interfaces that represent a structured JSON object that is being streamed.

In this guide, you will learn how to use the useObject hook in your application to generate UIs for structured data on the fly.

Example

The example shows a small notifications demo app that generates fake notifications in real-time.

Schema

It is helpful to set up the schema in a separate file that is imported on both the client and server.

import { z } from 'zod';

// define a schema for the notifications
export const notificationSchema = z.object({
  notifications: z.array(
    z.object({
      name: z.string().describe('Name of a fictional person.'),
      message: z.string().describe('Message. Do not use emojis or links.'),
    }),
  ),
});

Client

The client uses useObject to stream the object generation process.

The results are partial and are displayed as they are received. Please note the code for handling undefined values in the JSX.

'use client';

import { experimental_useObject as useObject } from '@ai-sdk/react';
import { notificationSchema } from './api/notifications/schema';

export default function Page() {
  const { object, submit } = useObject({
    api: '/api/notifications',
    schema: notificationSchema,
  });

  return (
    <>
      <button onClick={() => submit('Messages during finals week.')}>
        Generate notifications
      </button>

      {object?.notifications?.map((notification, index) => (
        <div key={index}>
          <p>{notification?.name}</p>
          <p>{notification?.message}</p>
        </div>
      ))}
    </>
  );
}

Server

On the server, we use streamText with Output.object() to stream the object generation process.

import { streamText, Output } from 'ai';
import { openai } from '@ai-sdk/openai';
import { notificationSchema } from './schema';

// Allow streaming responses up to 30 seconds
export const maxDuration = 30;

export async function POST(req: Request) {
  const context = await req.json();

  const result = streamText({
    model: openai('gpt-4-turbo'),
    output: Output.object({ schema: notificationSchema }),
    prompt:
      `Generate 3 notifications for a messages app in this context:` + context,
  });

  return result.toTextStreamResponse();
}

Enum Output Mode

When you need to classify or categorize input into predefined options, you can use the enum output mode with useObject. This requires a specific schema structure where the object has enum as a key with z.enum containing your possible values.

Example: Text Classification

This example shows how to build a simple text classifier that categorizes statements as true or false.

Client

When using useObject with enum output mode, your schema must be an object with enum as the key:

'use client';

import { experimental_useObject as useObject } from '@ai-sdk/react';
import { z } from 'zod';

export default function ClassifyPage() {
  const { object, submit, isLoading } = useObject({
    api: '/api/classify',
    schema: z.object({ enum: z.enum(['true', 'false']) }),
  });

  return (
    <>
      <button onClick={() => submit('The earth is flat')} disabled={isLoading}>
        Classify statement
      </button>

      {object && <div>Classification: {object.enum}</div>}
    </>
  );
}

Server

On the server, use streamText with Output.choice() to stream the classification result:

import { streamText, Output } from 'ai';
import { openai } from '@ai-sdk/openai';

export async function POST(req: Request) {
  const context = await req.json();

  const result = streamText({
    model: openai('gpt-4-turbo'),
    output: Output.choice({ options: ['true', 'false'] }),
    prompt: `Classify this statement as true or false: ${context}`,
  });

  return result.toTextStreamResponse();
}

Customized UI

useObject also provides ways to show loading and error states:

Loading State

The isLoading state returned by the useObject hook can be used for several purposes:

• To show a loading spinner while the object is generated.
• To disable the submit button.

'use client';

import { experimental_useObject as useObject } from '@ai-sdk/react';

export default function Page() {
  const { isLoading, object, submit } = useObject({
    api: '/api/notifications',
    schema: notificationSchema,
  });

  return (
    <>
      {isLoading && <Spinner />}

      <button
        onClick={() => submit('Messages during finals week.')}
        disabled={isLoading}
      >
        Generate notifications
      </button>

      {object?.notifications?.map((notification, index) => (
        <div key={index}>
          <p>{notification?.name}</p>
          <p>{notification?.message}</p>
        </div>
      ))}
    </>
  );
}

Stop Handler

The stop function can be used to stop the object generation process. This can be useful if the user wants to cancel the request or if the server is taking too long to respond.

'use client';

import { experimental_useObject as useObject } from '@ai-sdk/react';

export default function Page() {
  const { isLoading, stop, object, submit } = useObject({
    api: '/api/notifications',
    schema: notificationSchema,
  });

  return (
    <>
      {isLoading && (
        <button type="button" onClick={() => stop()}>
          Stop
        </button>
      )}

      <button onClick={() => submit('Messages during finals week.')}>
        Generate notifications
      </button>

      {object?.notifications?.map((notification, index) => (
        <div key={index}>
          <p>{notification?.name}</p>
          <p>{notification?.message}</p>
        </div>
      ))}
    </>
  );
}

Error State

Similarly, the error state reflects the error object thrown during the fetch request. It can be used to display an error message, or to disable the submit button:

We recommend showing a generic error message to the user, such as “Something went wrong.” This is a good practice to avoid leaking information from the server.

'use client';

import { experimental_useObject as useObject } from '@ai-sdk/react';

export default function Page() {
  const { error, object, submit } = useObject({
    api: '/api/notifications',
    schema: notificationSchema,
  });

  return (
    <>
      {error && <div>An error occurred.</div>}

      <button onClick={() => submit('Messages during finals week.')}>
        Generate notifications
      </button>

      {object?.notifications?.map((notification, index) => (
        <div key={index}>
          <p>{notification?.name}</p>
          <p>{notification?.message}</p>
        </div>
      ))}
    </>
  );
}

Event Callbacks

useObject provides optional event callbacks that you can use to handle life-cycle events.

• onFinish: Called when the object generation is completed.
• onError: Called when an error occurs during the fetch request.

These callbacks can be used to trigger additional actions, such as logging, analytics, or custom UI updates.

'use client';

import { experimental_useObject as useObject } from '@ai-sdk/react';
import { notificationSchema } from './api/notifications/schema';

export default function Page() {
  const { object, submit } = useObject({
    api: '/api/notifications',
    schema: notificationSchema,
    onFinish({ object, error }) {
      // typed object, undefined if schema validation fails:
      console.log('Object generation completed:', object);

      // error, undefined if schema validation succeeds:
      console.log('Schema validation error:', error);
    },
    onError(error) {
      // error during fetch request:
      console.error('An error occurred:', error);
    },
  });

  return (
    <div>
      <button onClick={() => submit('Messages during finals week.')}>
        Generate notifications
      </button>

      {object?.notifications?.map((notification, index) => (
        <div key={index}>
          <p>{notification?.name}</p>
          <p>{notification?.message}</p>
        </div>
      ))}
    </div>
  );
}

Configure Request Options

You can configure the API endpoint, optional headers and credentials using the api, headers and credentials settings.

const { submit, object } = useObject({
  api: '/api/use-object',
  headers: {
    'X-Custom-Header': 'CustomValue',
  },
  credentials: 'include',
  schema: yourSchema,
});