2nd/10_Wiki/Topic_Programming/Frontend/Pinia.md

id, title, category, status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, verification_status, tags, raw_sources, last_reinforced, github_commit, tech_stack

id	title	category	status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	verification_status	tags	raw_sources	last_reinforced	github_commit	tech_stack
wiki-2026-0508-pinia	Pinia	10_Wiki/Topics	verified	self	Vue Store Pinia Store	none	A	0.9	applied	vue state-management frontend		2026-05-10	pending	language framework TypeScript Vue 3 / Pinia 2

Pinia

매 한 줄

"매 Vue 3 매 official state management — 매 Vuex 4 후속, 매 Composition API native + 매 TypeScript-first". Eduardo San Martin Morote 매 2019 발표 매 Vue Core 팀 채택, 매 store 매 composable function 매 표현 매 boilerplate 90% 감소, 매 2026 매 Vue 표준 store library.

매 핵심

매 vs Vuex

• No mutations: 매 actions 가 directly state 수정 — 매 mutation indirection 제거.
• Flat stores: 매 nested module 매 X — 매 cross-store import 매 graph 형성.
• Type inference: 매 zero manual typing — 매 store usage 매 fully typed.
• Devtools: 매 timeline + state inspect + time-travel 지원.

매 store kinds

• Options Store: state, getters, actions — 매 Vuex-like familiar shape.
• Setup Store: ref/computed/function — 매 Composition API native.

매 응용

1. SPA global state (auth, user prefs).
2. Server-side rendering (Nuxt 3 매 native integration).
3. Cross-component caching (API result, derived state).
4. Plugin extension (persistedstate, undo/redo).

💻 패턴

Setup store (modern preferred)

// stores/counter.ts
import { defineStore } from 'pinia'
import { ref, computed } from 'vue'

export const useCounterStore = defineStore('counter', () => {
  const count = ref(0)
  const doubled = computed(() => count.value * 2)
  function increment() { count.value++ }
  function reset() { count.value = 0 }
  return { count, doubled, increment, reset }
})

Options store

export const useUserStore = defineStore('user', {
  state: () => ({
    user: null as User | null,
    loading: false,
  }),
  getters: {
    isLoggedIn: (s) => s.user !== null,
    displayName: (s) => s.user?.name ?? 'Guest',
  },
  actions: {
    async login(creds: Credentials) {
      this.loading = true
      try {
        this.user = await api.login(creds)
      } finally {
        this.loading = false
      }
    },
    logout() { this.user = null },
  },
})

Component usage

<script setup lang="ts">
import { storeToRefs } from 'pinia'
import { useCounterStore } from '@/stores/counter'

const store = useCounterStore()
// 매 reactivity 매 유지: storeToRefs 매 ref 변환
const { count, doubled } = storeToRefs(store)
// actions 매 destructure OK (not reactive)
const { increment } = store
</script>

<template>
  <button @click="increment">{{ count }} (×2 = {{ doubled }})</button>
</template>

App setup (Vue 3)

// main.ts
import { createApp } from 'vue'
import { createPinia } from 'pinia'
import App from './App.vue'

const app = createApp(App)
app.use(createPinia())
app.mount('#app')

Cross-store usage

import { useAuthStore } from './auth'

export const useCartStore = defineStore('cart', () => {
  const auth = useAuthStore() // 매 다른 store 매 import + use
  const items = ref<CartItem[]>([])

  async function checkout() {
    if (!auth.isLoggedIn) throw new Error('Login required')
    return api.checkout(auth.user!.id, items.value)
  }
  return { items, checkout }
})

$patch 매 batch update

const store = useUserStore()
store.$patch({ loading: false, user: newUser }) // 매 single devtools entry
// or function form for complex mutations
store.$patch((state) => {
  state.cart.push(item)
  state.lastUpdated = Date.now()
})

$subscribe 매 store mutation 감지

store.$subscribe((mutation, state) => {
  localStorage.setItem('cart', JSON.stringify(state))
}, { detached: true })

Plugin (persistedstate)

import { createPinia } from 'pinia'
import piniaPersist from 'pinia-plugin-persistedstate'

const pinia = createPinia()
pinia.use(piniaPersist)

// store 정의 시:
export const useUserStore = defineStore('user', {
  state: () => ({ token: '' }),
  persist: true, // localStorage 매 자동 sync
})

SSR (Nuxt 3)

// composables/useAuth.ts
export const useAuthStore = defineStore('auth', () => {
  const user = ref<User | null>(null)
  // 매 Nuxt 3 매 자동 hydration — server 매 set 한 state 매 client 매 transfer
  return { user }
})

Testing

import { setActivePinia, createPinia } from 'pinia'
import { beforeEach, expect, test } from 'vitest'

beforeEach(() => setActivePinia(createPinia()))

test('counter increments', () => {
  const store = useCounterStore()
  expect(store.count).toBe(0)
  store.increment()
  expect(store.count).toBe(1)
  expect(store.doubled).toBe(2)
})

매 결정 기준

상황	Approach
Vue 3 new project	Pinia (default)
Vuex 4 migration	Pinia (incremental, alias module)
Composition API preference	Setup store
Vuex-familiar team	Options store
Component-local state	ref/reactive (no store)
Server state caching	TanStack Query / 매 store 의 X
SSR (Nuxt)	Pinia (built-in support)

기본값: 매 setup store + TypeScript + storeToRefs.

🔗 Graph

• 부모: State Management
• 변형: Vuex (predecessor) · 프론트엔드 및 UIUX 표준 · Zustand · Jotai
• 응용: Nuxt
• Adjacent: Composition-API

🤖 LLM 활용

언제: 매 Vue 3 global state, 매 cross-component sharing, 매 Nuxt 3 SSR state, 매 Vuex migration target. 언제 X: 매 component-local state (ref 만 충분), 매 server cache (TanStack Query 적합), 매 React project (Zustand/Redux).

❌ 안티패턴

• storeToRefs 없이 destructure: 매 reactivity loss — 매 const { count } = store 의 X.
• Store action 매 component logic 침범: 매 store 매 단순 state holder 매 됨 — 매 business logic 매 store 에 응집.
• Nested store hierarchy 시도: 매 flat 의 X — 매 cross-import 매 graph 형성.
• Mutation pattern 의 반복: 매 Vuex habit — 매 action 에서 직접 state 수정 OK.
• 매 component 매 store instance 다중 생성: 매 useStore() 매 singleton — 매 매 호출 동일 instance.

🧪 검증 / 중복

• Verified (Pinia 2.x docs, Vue.js official).
• 신뢰도 A.

🕓 Changelog

날짜	변경
2026-05-08	Phase 1
2026-05-10	Manual cleanup — setup/options store + cross-store + SSR + plugin patterns