qcast-front/.agents/skills/next-best-practices/directives.md

Directives

React Directives

These are React directives, not Next.js specific.

'use client'

Marks a component as a Client Component. Required for:

• React hooks (useState, useEffect, etc.)
• Event handlers (onClick, onChange)
• Browser APIs (window, localStorage)

'use client'

import { useState } from 'react'

export function Counter() {
  const [count, setCount] = useState(0)
  return <button onClick={() => setCount(count + 1)}>{count}</button>
}

Reference: https://react.dev/reference/rsc/use-client

'use server'

Marks a function as a Server Action. Can be passed to Client Components.

'use server'

export async function submitForm(formData: FormData) {
  // Runs on server
}

Or inline within a Server Component:

export default function Page() {
  async function submit() {
    'use server'
    // Runs on server
  }
  return <form action={submit}>...</form>
}

Reference: https://react.dev/reference/rsc/use-server

---

Next.js Directive

'use cache'

Marks a function or component for caching. Part of Next.js Cache Components.

'use cache'

export async function getCachedData() {
  return await fetchData()
}

Requires cacheComponents: true in next.config.ts.

For detailed usage including cache profiles, cacheLife(), cacheTag(), and updateTag(), see the next-cache-components skill.

Reference: https://nextjs.org/docs/app/api-reference/directives/use-cache