---
id: react-rhf-zod-patterns
title: React Hook Form + Zod — 폼 / 검증 / 에러
category: Coding
status: draft
source_trust_level: B
verification_status: conceptual
created_at: 2026-05-09
updated_at: 2026-05-09
tags: [react, react-hook-form, zod, form, vibe-coding]
tech_stack: { language: "TS / React", applicable_to: ["Frontend"] }
applied_in: []
aliases: [RHF, useForm, zodResolver, register, Controller, server validation]
---

# React Hook Form + Zod

> 가벼운 + 빠른 폼. **Zod schema 가 진실 source — type 도 검증도**. RHF + zodResolver + shadcn/ui Form 이 표준 조합.

## 📖 핵심 개념
- Uncontrolled by default: ref 기반, re-render 적음.
- Controller: 외부 컴포넌트 wrap (MUI / Radix).
- Zod schema: type infer + parse + 에러 포맷.
- defaultValues: undefined 안 넣기.

## 💻 코드 패턴

### 기본
```tsx
import { useForm } from 'react-hook-form';
import { zodResolver } from '@hookform/resolvers/zod';
import { z } from 'zod';

const schema = z.object({
  email: z.string().email(),
  password: z.string().min(8),
  remember: z.boolean().default(false),
});

type Form = z.infer<typeof schema>;

function Login() {
  const { register, handleSubmit, formState: { errors, isSubmitting } } = useForm<Form>({
    resolver: zodResolver(schema),
    defaultValues: { email: '', password: '', remember: false },
  });

  const onSubmit = async (data: Form) => {
    await api.login(data);
  };

  return (
    <form onSubmit={handleSubmit(onSubmit)}>
      <input {...register('email')} />
      {errors.email && <span>{errors.email.message}</span>}

      <input type="password" {...register('password')} />
      {errors.password && <span>{errors.password.message}</span>}

      <label><input type="checkbox" {...register('remember')} /> Remember</label>

      <button disabled={isSubmitting}>Login</button>
    </form>
  );
}
```

### Controller (외부 컴포넌트)
```tsx
import { Controller } from 'react-hook-form';
import { Select } from '@radix-ui/react-select';

<Controller
  name="country"
  control={control}
  render={({ field }) => (
    <Select value={field.value} onValueChange={field.onChange}>
      ...
    </Select>
  )}
/>
```

### Server-side errors
```tsx
const onSubmit = async (data: Form) => {
  try {
    await api.login(data);
  } catch (e) {
    if (e.code === 'EMAIL_TAKEN') {
      setError('email', { type: 'server', message: '이미 사용중' });
    } else {
      setError('root.serverError', { message: '서버 오류' });
    }
  }
};

// root error 표시
{errors.root?.serverError && <p>{errors.root.serverError.message}</p>}
```

### Field array (동적 list)
```tsx
const { control, register } = useForm({ defaultValues: { items: [{ name: '', qty: 1 }] } });
const { fields, append, remove } = useFieldArray({ control, name: 'items' });

{fields.map((f, i) => (
  <div key={f.id}>
    <input {...register(`items.${i}.name`)} />
    <input type="number" {...register(`items.${i}.qty`, { valueAsNumber: true })} />
    <button onClick={() => remove(i)}>x</button>
  </div>
))}
<button onClick={() => append({ name: '', qty: 1 })}>+</button>
```

### Watch + computed
```tsx
const password = watch('password');
const strength = useMemo(() => calcStrength(password), [password]);
```

### Conditional schema
```ts
const schema = z.discriminatedUnion('type', [
  z.object({ type: z.literal('email'), email: z.string().email() }),
  z.object({ type: z.literal('phone'), phone: z.string().regex(/^\d{10}$/) }),
]);
```

### shadcn/ui Form
```tsx
<Form {...form}>
  <form onSubmit={form.handleSubmit(onSubmit)}>
    <FormField
      control={form.control}
      name="email"
      render={({ field }) => (
        <FormItem>
          <FormLabel>Email</FormLabel>
          <FormControl><Input {...field} /></FormControl>
          <FormMessage />
        </FormItem>
      )}
    />
  </form>
</Form>
```

### Server schema 공유 (Backend + Frontend)
```ts
// shared package
export const LoginSchema = z.object({...});

// frontend: zodResolver(LoginSchema)
// backend: LoginSchema.parse(req.body)
```

### Trigger validation manually
```tsx
const valid = await trigger('email');
if (valid) goNextStep();
```

## 🤔 의사결정 기준
| 상황 | 추천 |
|---|---|
| 일반 폼 | RHF + zodResolver |
| 서버 컴포넌트 (Next 14+) | Server actions + zod-form-data |
| 매우 간단 | useState 충분 |
| Wizard / multi-step | RHF + form context |
| File upload | RHF + Controller |
| Real-time validation | mode: 'onChange' (debounce 권장) |

## ❌ 안티패턴
- **defaultValues undefined**: uncontrolled→controlled warning. 빈 문자열.
- **Type 직접 정의 — schema 따로**: drift. infer 활용.
- **Controller 안 써도 되는데 사용**: re-render 비용.
- **모든 onChange validation**: 빠른 입력 시 jank. mode: 'onBlur' 또는 'onTouched'.
- **mutate 매번 reset 안 함**: 다음 폼에 stale 값.
- **숫자 input string 으로**: `valueAsNumber: true`.
- **Server validation 없음**: client 만 — bypass 가능.

## 🤖 LLM 활용 힌트
- RHF + zodResolver + shadcn Form 3종.
- Schema = 한 곳 (frontend/backend 공유).
- Server error → setError('root.serverError').

## 🔗 관련 문서
- [[React_Form_State_Patterns]]
- [[AI_Structured_Output_Zod]]
