Mutations

Unlike queries, mutations are typically used to create, update, delete data or perform server side-effects. For this purpose, Vue Query exports a useMutation hook.

Here's an example of a mutation that adds a new todo to the server:

vue

<script setup>
import { useMutation } from "vue-query";

function useAddTodoMutation() {
  return useMutation((newTodo) => axios.post("/todos", newTodo));
}

const { isLoading, isError, error, isSuccess, mutate } = useAddTodoMutation();

function addTodo() {
  mutate({ id: new Date(), title: 'Do Laundry' });
}
</script>

<template>
  <span v-if="isLoading">Adding todo...</span>
  <span v-else-if="isError">An error occurred: {{ error.message }}</span>
  <span v-else-if="isSuccess">Todo added!</span>
  <button @click="addTodo">Create Todo</button>
</template>

A mutation can only be in one of the following states at any given moment:

isIdle or status === 'idle' - The mutation is currently idle or in a fresh/reset state
isLoading or status === 'loading' - The mutation is currently running.
isError or status === 'error' - The mutation encountered an error.
isSuccess or status === 'success' - The mutation was successful and the mutation data is available.

Beyond those primary states, more information is available depending on the state of the mutation:

error - If the mutation is in an error state, the error is available via the error property.
data - If the mutation is in a success state, the data is available via the data property.

In the example above, you also saw that you can pass variables to your mutations function by calling the mutate function with a single variable or object.

Even with just variables, mutations aren't all that special, but when used with the onSuccess option, the Query Client's invalidateQueries method and the Query Client's setQueryData method, mutations become a very powerful tool.

Resetting Mutation State

In the case that you need to clear the error or data of a mutation request. You can use the reset function to handle this:

vue

<script>
import { useMutation } from "vue-query";

function useAddTodoMutation() {
  return useMutation((newTodo) => axios.post("/todos", newTodo));
}

const { error, mutate, reset } = useAddTodoMutation();

function addTodo() {
  mutate({ id: new Date(), title: "Do Laundry" });
}
</script>

<template>
  <span v-else-if="error">
    <span>An error occurred: {{ error.message }}</span>
    <button @click="reset">Reset error</button>
  </span>
  <button @click="addTodo">Create Todo</button>
</template>

Mutation side effects

useMutation comes with some helper options that allow quick and easy side-effects at any stage during the mutation lifecycle. These come in handy for both invalidating and refetching queries after mutations and even optimistic updates.

function useAddTodoMutation() {
  return useMutation((newTodo) => axios.post("/todos", newTodo), {
    onMutate: (variables) => {
      // A mutation is about to happen!

      // Optionally return a context containing data to use when for example rolling back
      return { id: 1 };
    },
    onError: (error, variables, context) => {
      // An error happened!
      console.log(`rolling back optimistic update with id ${context.id}`);
    },
    onSuccess: (data, variables, context) => {
      // Boom baby!
    },
    onSettled: (data, error, variables, context) => {
      // Error or success... doesn't matter!
    },
  });
}

When returning a promise in any of the callback functions it will first be awaited before the next callback is called:

function useAddTodoMutation() {
  return useMutation((newTodo) => axios.post("/todos", newTodo), {
    onSuccess: async () => {
      console.log("I'm first!");
    },
    onSettled: async () => {
      console.log("I'm second!");
    },
  });
}

You might find that you want to trigger additional callbacks than the ones defined on useMutation when calling mutate. This can be used to trigger component-specific side effects. To do that, you can provide any of the same callback options to the mutate function after your mutation variable. Supported overrides include: onSuccess, onError and onSettled. Please keep in mind that those additional callbacks won't run if your component unmounts before the mutation finishes.

function useAddTodoMutation() {
  return useMutation((newTodo) => axios.post("/todos", newTodo), {
    onSuccess: (data, variables, context) => {
      // I will fire first
    },
    onError: (error, variables, context) => {
      // I will fire first
    },
    onSettled: (data, error, variables, context) => {
      // I will fire first
    },
  });
}

const { mutate } = useAddTodoMutation();

mutate(todo, {
  onSuccess: (data, variables, context) => {
    // I will fire second!
  },
  onError: (error, variables, context) => {
    // I will fire second!
  },
  onSettled: (data, error, variables, context) => {
    // I will fire second!
  },
});

Promises

Use mutateAsync instead of mutate to get a promise which will resolve on success or throw on an error. This can for example be used to compose side effects.

const { mutateAsync } = useAddTodoMutation();

function myAction() {
  try {
    const todo = await mutateAsync(todo);
    console.log(todo);
  } catch (error) {
    console.error(error);
  } finally {
    console.log("done");
  }
}

Retry

By default Vue Query will not retry a mutation on error, but it is possible with the retry option:

const mutation = useMutation(addTodo, {
  retry: 3,
});

If mutations fail because the device is offline, they will be retried in the same order when the device reconnects.

Persist mutations

Mutations can be persisted to storage if needed and resumed at a later point. This can be done with the hydration functions:

const queryClient = new QueryClient();

// Define the "addTodo" mutation
queryClient.setMutationDefaults("addTodo", {
  mutationFn: addTodo,
  onMutate: async (variables) => {
    // Cancel current queries for the todos list
    await queryClient.cancelQueries("todos");

    // Create optimistic todo
    const optimisticTodo = { id: uuid(), title: variables.title };

    // Add optimistic todo to todos list
    queryClient.setQueryData("todos", (old) => [...old, optimisticTodo]);

    // Return context with the optimistic todo
    return { optimisticTodo };
  },
  onSuccess: (result, variables, context) => {
    // Replace optimistic todo in the todos list with the result
    queryClient.setQueryData("todos", (old) =>
      old.map((todo) => (todo.id === context.optimisticTodo.id ? result : todo))
    );
  },
  onError: (error, variables, context) => {
    // Remove optimistic todo from the todos list
    queryClient.setQueryData("todos", (old) =>
      old.filter((todo) => todo.id !== context.optimisticTodo.id)
    );
  },
  retry: 3,
});

// Start mutation in some component:
const mutation = useMutation("addTodo");
mutation.mutate({ title: "title" });

// If the mutation has been paused because the device is for example offline,
// Then the paused mutation can be dehydrated when the application quits:
const state = dehydrate(queryClient);

// The mutation can then be hydrated again when the application is started:
hydrate(queryClient, state);

// Resume the paused mutations:
queryClient.resumePausedMutations();

Mutations ​

Resetting Mutation State ​

Mutation side effects ​

Promises ​

Retry ​

Persist mutations ​