Vue Academy · Lesson

defineStore: State, Getters, Actions

Options store vs Setup store, state as function, computed getters, async actions.

Lesson 2 of 413 steps

defineStore: State, Getters, Actions is a free Vue Academy lesson on CoddyKit. This is lesson 2 of 4. Any 3 lessons of this learning path are free to read in full — after that, CoddyKit PRO unlocks every lesson, plus hands-on practice with a built-in code editor and a 24/7 AI tutor. It is part of the Vue Academy learning path, and your progress syncs across the web and the CoddyKit app. The Vue Academy course includes 4 lessons in total.

The Three Pillars of a Store

An option store has three parts: state (the data), getters (derived values), and actions (methods that change state). You define all three inside defineStore.

Defining a Store

defineStore takes a unique id string and an options object. It returns a composable — by convention named useXxxStore.

import { defineStore } from 'pinia'

export const useCounterStore = defineStore('counter', {
  // state, getters, actions go here
})

State Is a Function

The state option must be a function returning an object. This guarantees each store instance gets a fresh state, just like data() in components.

export const useCounterStore = defineStore('counter', {
  state: () => ({ count: 0, name: 'Coddy' })
})

Reading State

Call the store composable inside setup to get an instance, then read state properties directly. They are reactive.

const counter = useCounterStore()
console.log(counter.count) // 0

Getters Are Computed Values

getters are like computed properties. Each receives the state as its first argument and returns a derived value. They are cached.

export const useCounterStore = defineStore('counter', {
  state: () => ({ count: 2 }),
  getters: {
    doubled: (s) => s.count * 2
  }
})

Using a Getter

Access a getter like a property — no parentheses. Pinia recomputes it only when its dependencies change.

const counter = useCounterStore()
console.log(counter.doubled) // 4

Getters Referencing Other Getters

To use another getter, reference this instead of the state parameter. With this, do not use an arrow function.

getters: {
  doubled: (s) => s.count * 2,
  quadrupled() {
    return this.doubled * 2
  }
}

Actions Change State

actions are methods. They use this to read and mutate state directly. No commit, no dispatch — just call the method.

export const useCounterStore = defineStore('counter', {
  state: () => ({ count: 0 }),
  actions: {
    increment() { this.count++ },
    addBy(amount) { this.count += amount }
  }
})

Async Actions

Actions can be async. This is the place for API calls — fetch data, then assign the result to state.

actions: {
  async loadUser(id) {
    const res = await fetch('/api/users/' + id)
    this.user = await res.json()
  }
}

Using the Store in a Component

Import the composable, call it in <script setup>, and use state, getters, and actions in the template.

<script setup>
import { useCounterStore } from '@/stores/counter'
const counter = useCounterStore()
</script>

<template>
  <p>{{ counter.count }} -> {{ counter.doubled }}</p>
  <button @click="counter.increment()">+</button>
</template>

Patching Multiple Fields

To change several state fields at once, use $patch. It groups the changes into a single devtools entry.

counter.$patch({ count: 10, name: 'New' })

Quick Check

Test your knowledge of option store structure.

Answer it in the interactive lesson

Recap

An option store has three parts:

state: a function returning the data object.
getters: cached derived values, receive state (or use this).
actions: methods that mutate state directly via this.

Use the store by calling its composable inside setup.

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Frequently Asked Questions

Is the “defineStore: State, Getters, Actions” lesson free?

Yes — any 3 lessons of the Vue Academy learning path, including “defineStore: State, Getters, Actions”, are free to read in full here on the web. After that, CoddyKit PRO unlocks every lesson, plus interactive practice with a built-in code editor and a 24/7 AI tutor. The Vue Academy course includes 4 lessons in total.

What will I learn in “defineStore: State, Getters, Actions”?

Options store vs Setup store, state as function, computed getters, async actions. You practise Vue Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Vue Academy?

No prior experience is required. Vue Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 2 of 4.

How long does the “defineStore: State, Getters, Actions” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

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