Mutations

Mutations alllow us to trigger and track the status of an async operation meant to have side effects. While queries are meant to read data, mutations are meant to write data. In terms of REST, queries handle GET requests and mutations handle POST, PUT, PATCH, and DELETE requests (without limiting you to do so).

Similarly to queries, mutations are defined with the useMutation() composable:

<script setup lang="ts">
import { ref } from 'vue'
import { useMutation } from '@pinia/colada'

const { mutate, status } = useMutation({
  mutation: (todoText: string) =>
    fetch('/api/todos', {
      method: 'POST',
      body: JSON.stringify({ text: todoText }),
    }),
})

const todoText = ref('')
function createTodo() {
  mutate(todoText.value)
}
</script>

<template>
  <form @submit.prevent="createTodo()">
    <input v-model="todoText">
    <button :disabled="status === 'loading'">
      Add todo
    </button>
  </form>
</template>

Alternatively, they can be defined with the defineMutation() function, which allows you to create related properties (like the todoText above) associated with the mutation:

mutations/todos.ts

// NOTE: to sync with mutations.md
import { ref } from 'vue'
import { defineMutation, useMutation } from '@pinia/colada'

export const useCreateTodo = defineMutation(() => {
  const todoText = ref('')
  const mutation = useMutation({
    mutation: () =>
      fetch('/api/todos', {
        method: 'POST',
        body: JSON.stringify({ text: todoText.value }),
      }),

  })

  return {
    ...mutation,
    createTodo: mutation.mutate,
    // expose the todoText ref
    todoText,
  }
})

components/CreateTodo.vue

<script setup lang="ts">
import { ref } from 'vue'
import { useCreateTodo } from './mutations/todos'

const { createTodo, status } = useCreateTodo()
// FIXME: should be part of useCreateTodo
const todoText = ref('')
</script>

<template>
  <form @submit.prevent="() => {}">
    <input v-model="todoText">
    <button :disabled="status === 'loading'">
      Add todo
    </button>
  </form>
</template>

TODO:

• Executing mutations
• Status of mutations
• Side effects
  • note about invalidating queries
  • Optimistic updates
• Global options

Best Practices