useOptimisticAction

info

useOptimisticAction does not wait for the action to finish execution before returning the optimistic data. It is then synced with the real result from server when the action has finished its execution. If you need to perform normal mutations, use useAction instead.

warning

This hook uses an experimental hook from React called useOptimistic under the hood. For this reason, you might experience some bugs and breaking changes in the future.

Let's say, you want to update the number of likes of a post in your application, mutating directly the database.

Example

1. Define a new action called addLikes, that takes an amount as input and returns the updated number of likes:

const schema = z.object({
  amount: z.number().positive(),
});

// Fake database.
let likes = 42;
export const getLikes = () => likes;

export const addLikes = actionClient
  .schema(schema)
  .define(async ({ parsedInput: { amount } }) => {
    await new Promise((resolve) => setTimeout(resolve, 1000));

    // Mutate data in fake db. This would be a database call in the real world.
    likes += amount;

    // We use this function to revalidate server state.
    // More information about it here:
    // https://nextjs.org/docs/app/api-reference/functions/revalidatePath
    revalidatePath("/");

    return { numOfLikes: likes };
});

2. Then, in your Server Component, you need to pass the current number of likes to the Client Component:

export default function Home() {
  return (
    <main>
      {/* Here we pass current number of likes to the Client Component.
      This is updated on the server every time the action is executed, since we
      used `revalidatePath()` inside action's server code. */}
      <AddLikes numOfLikes={getLikes()} />
    </main>
  );
}

3. Finally, in your Client Component, you can use it like this:

import { useOptimisticAction } from "next-safe-action/hooks";
import { addLikes } from "@/app/add-likes-action";

type Props = {
  numOfLikes: number;
}

export default function AddLikes({ numOfLikes }: Props) {
  const { execute, result, optimisticData } = useOptimisticAction(
    addLikes,
    { numOfLikes },
    (state, { amount }) => {
      return { numOfLikes: state.numOfLikes + amount };
    }
  );

  return (
    <div>
      <button
        onClick={() => {
          execute({ amount: 3 });
        }}>
        Add 3 likes
      </button>
      {/* Optimistic state gets updated immediately, it doesn't wait for the server to respond. */}
      <pre>Optimistic state: {optimisticData.numOfLikes}</pre>

      {/* Here's the actual server response. */}
      <pre>Result: {JSON.stringify(result, null, 2)}</pre>
    </div>
  );
}

useOptimisticAction arguments

useOptimisticAction has the following arguments:

Name	Type	Purpose
safeActionFn	SafeActionFn	This is the action that will be called when you use execute from hook's return object.
initialOptimisticData	Data (return type of the safeActionFn you passed as first argument)	An initializer for the optimistic state. Usually this value comes from the parent Server Component.
reducer	(state: Data, input: InferIn<S>) => Data	When you call the action via execute, this function determines how the optimistic update is performed. Basically, here you define what happens immediately after execute is called, and before the actual result comes back from the server.
callbacks?	HookCallbacks	Optional callbacks. More information about them here.

useOptimisticAction return object

useOptimisticAction returns an object with the following properties:

Name	Type	Purpose
execute	(input: InferIn<S>) => void	An action caller with no return. The input is the same as the safe action you passed to the hook.
result	HookResult	When the action gets called via execute, this is the result object.
status	HookActionStatus	The action current status.
reset	() => void	You can programmatically reset the result object with this function.
optimisticData	Data (return type of the safeActionFn you passed as first argument)	This is the data that gets updated immediately after execute is called, with the behavior you defined in the reducer function hook argument. The initial state is what you provided to the hook via initialOptimisticData argument.

Explore a working example here.