[Django] Formsets: 여러 폼 동시 처리

Django formset, modelformset, inlineformset, management form, formset factory

정의

Formset = 여러 폼을 한 페이지에서 동시 처리. “상품 3개 한 번에 등록”, “주문 상세 여러 줄 편집” 같은 시나리오.

3가지 종류

flowchart TD
    Q{Formset 종류}
    Q --> A["FormSet<br/>(일반 Form 반복)"]
    Q --> B["ModelFormSet<br/>(같은 모델 여러 개)"]
    Q --> C["InlineFormSet<br/>(부모 모델의 자식들)"]

1. 기본 FormSet

from django import forms
from django.forms import formset_factory

class ContactForm(forms.Form):
    name = forms.CharField()
    email = forms.EmailField()

ContactFormSet = formset_factory(
    ContactForm,
    extra=2,        # 빈 폼 개수
    max_num=10,     # 최대 개수
    can_delete=True,
)

def contacts_view(request):
    if request.method == 'POST':
        formset = ContactFormSet(request.POST)
        if formset.is_valid():
            for form in formset:
                if form.cleaned_data.get('DELETE'):
                    continue
                name = form.cleaned_data['name']
                email = form.cleaned_data['email']
                # 저장 로직
    else:
        formset = ContactFormSet()
    return render(request, 'contacts.html', {'formset': formset})

Template + Management Form

<form method="post">
  {% csrf_token %}
  {{ formset.management_form }}   <!-- 필수! -->
  {% for form in formset %}
    <div class="form-row">
      {{ form.as_p }}
    </div>
  {% endfor %}
  <button type="submit">저장</button>
</form>

Management form 이 렌더링:

<input type="hidden" name="form-TOTAL_FORMS" value="2">
<input type="hidden" name="form-INITIAL_FORMS" value="0">
<input type="hidden" name="form-MIN_NUM_FORMS" value="0">
<input type="hidden" name="form-MAX_NUM_FORMS" value="10">

2. ModelFormSet

from django.forms import modelformset_factory

ProductFormSet = modelformset_factory(
    Product,
    fields=('name', 'price', 'stock'),
    extra=1,
    can_delete=True,
)

def products_admin(request):
    if request.method == 'POST':
        formset = ProductFormSet(request.POST, queryset=Product.objects.filter(active=True))
        if formset.is_valid():
            formset.save()
    else:
        formset = ProductFormSet(queryset=Product.objects.filter(active=True))
    return render(request, 'products.html', {'formset': formset})

3. InlineFormSet (부모-자식)

from django.forms import inlineformset_factory

# Author 하나에 여러 Book
BookFormSet = inlineformset_factory(
    Author,          # 부모
    Book,            # 자식
    fields=('title', 'published_at'),
    extra=1,
    can_delete=True,
)

def edit_author(request, author_id):
    author = Author.objects.get(pk=author_id)
    if request.method == 'POST':
        formset = BookFormSet(request.POST, instance=author)
        if formset.is_valid():
            formset.save()   # 자동으로 author 지정!
    else:
        formset = BookFormSet(instance=author)
    return render(request, 'author_books.html', {'author': author, 'formset': formset})

동적 formset (JavaScript)

<form method="post">
  {% csrf_token %}
  {{ formset.management_form }}

  <div id="forms-container">
    {% for form in formset %}
      <div class="form-row">
        {{ form.as_p }}
      </div>
    {% endfor %}
  </div>

  <button type="button" onclick="addForm()">폼 추가</button>
  <button type="submit">저장</button>
</form>

<script>
function addForm() {
  const container = document.getElementById('forms-container');
  const totalForms = document.getElementById('id_form-TOTAL_FORMS');
  const idx = parseInt(totalForms.value);

  const template = container.children[0].outerHTML;
  const newForm = template.replaceAll(`form-0-`, `form-${idx}-`);
  container.insertAdjacentHTML('beforeend', newForm);

  totalForms.value = idx + 1;
}
</script>

Validation

class BaseContactFormSet(forms.BaseFormSet):
    def clean(self):
        """폼셋 전체 검증"""
        if any(self.errors):
            return

        emails = []
        for form in self.forms:
            if form.cleaned_data.get('DELETE'):
                continue
            email = form.cleaned_data.get('email')
            if email in emails:
                raise forms.ValidationError('이메일 중복 금지')
            emails.append(email)

ContactFormSet = formset_factory(
    ContactForm,
    formset=BaseContactFormSet,
    extra=2,
)

Ordering (순서 변경)

ContactFormSet = formset_factory(
    ContactForm,
    extra=2,
    can_order=True,   # ← 순서 변경 UI
)

Django 6.0 개선

• {{ formset.non_form_errors }} 렌더링 개선
• HTMX 통합 예시 문서 추가
• Type hints 강화

다른 프레임워크

Framework	여러 폼 처리
Django	formset_factory, inlineformset_factory
Rails	accepts_nested_attributes_for + fields_for
Spring	List binding + @Valid
HTMX + Alpine	동적 추가

흔한 함정

관련 위키

• django-forms
• django-modelforms
• django-views