Django 4.0.6 ドキュメント

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フォームセット (Formset)

class BaseFormSet

フォームセットとは、同じページで複数のフォームを扱うための抽象化レイヤで、いわばデータグリッドのようなものです。フォームセットを説明するために、まず以下のようなフォームを考えましょう。

>>> from django import forms
>>> class ArticleForm(forms.Form):
...     title = forms.CharField()
...     pub_date = forms.DateField()

このフォームを使って、ユーザが一度に複数の記事を作成できるようにしたいとします。ArticleForm からフォームセットを生成するには、次のようにします。

>>> from django.forms import formset_factory
>>> ArticleFormSet = formset_factory(ArticleForm)

You now have created a formset class named ArticleFormSet. Instantiating the formset gives you the ability to iterate over the forms in the formset and display them as you would with a regular form:

>>> formset = ArticleFormSet()
>>> for form in formset:
...     print(form.as_table())
<tr><th><label for="id_form-0-title">Title:</label></th><td><input type="text" name="form-0-title" id="id_form-0-title"></td></tr>
<tr><th><label for="id_form-0-pub_date">Pub date:</label></th><td><input type="text" name="form-0-pub_date" id="id_form-0-pub_date"></td></tr>

As you can see it only displayed one empty form. The number of empty forms that is displayed is controlled by the extra parameter. By default, formset_factory() defines one extra form; the following example will create a formset class to display two blank forms:

>>> ArticleFormSet = formset_factory(ArticleForm, extra=2)

Iterating over a formset will render the forms in the order they were created. You can change this order by providing an alternate implementation for the __iter__() method.

フォームセットでは、インデックスをつけて、一致するフォームを返すこともできます。__iter__ をオーバーライドした場合、動作を一貫させるため __getitem__ もオーバーライドする必要があります。

フォームセットで初期データを指定する

初期データは、フォームセットのユーザビリティに大きく影響します。上述したように、追加するフォーム数を指定できます。 これが意味するのは、初期データから生成するフォーム数に加えて、追加的なフォームをいくつ表示するかをフォームセットに指定している、ということです。以下の例を見てください:

>>> import datetime
>>> from django.forms import formset_factory
>>> from myapp.forms import ArticleForm
>>> ArticleFormSet = formset_factory(ArticleForm, extra=2)
>>> formset = ArticleFormSet(initial=[
...     {'title': 'Django is now open source',
...      'pub_date': datetime.date.today(),}
... ])

>>> for form in formset:
...     print(form.as_table())
<tr><th><label for="id_form-0-title">Title:</label></th><td><input type="text" name="form-0-title" value="Django is now open source" id="id_form-0-title"></td></tr>
<tr><th><label for="id_form-0-pub_date">Pub date:</label></th><td><input type="text" name="form-0-pub_date" value="2008-05-12" id="id_form-0-pub_date"></td></tr>
<tr><th><label for="id_form-1-title">Title:</label></th><td><input type="text" name="form-1-title" id="id_form-1-title"></td></tr>
<tr><th><label for="id_form-1-pub_date">Pub date:</label></th><td><input type="text" name="form-1-pub_date" id="id_form-1-pub_date"></td></tr>
<tr><th><label for="id_form-2-title">Title:</label></th><td><input type="text" name="form-2-title" id="id_form-2-title"></td></tr>
<tr><th><label for="id_form-2-pub_date">Pub date:</label></th><td><input type="text" name="form-2-pub_date" id="id_form-2-pub_date"></td></tr>

上の例では、今度は 3 つのフォームが表示されました。初期データとして渡された 1 つと、2 つの追加フォームです。初期データとして、辞書のリストを渡していることにも注意してください。

フォームセットを描画するために initial を使う場合、フォームセットの送信を処理するときに同じ initial を渡して、どのフォームがユーザによって変更されたかをフォームセットが検出できるようにしてください。例えば、ArticleFormSet(request.POST, initial=[...]) のようになるでしょう。

参考

モデルフォームセットを使ってモデルからフォームセットを作る.

フォームの最大表示数を制限する

formset_factory() に max_num パラメータを指定すると、フォームセット中に表示されるフォームの最大数を制限できます。

>>> from django.forms import formset_factory
>>> from myapp.forms import ArticleForm
>>> ArticleFormSet = formset_factory(ArticleForm, extra=2, max_num=1)
>>> formset = ArticleFormSet()
>>> for form in formset:
...     print(form.as_table())
<tr><th><label for="id_form-0-title">Title:</label></th><td><input type="text" name="form-0-title" id="id_form-0-title"></td></tr>
<tr><th><label for="id_form-0-pub_date">Pub date:</label></th><td><input type="text" name="form-0-pub_date" id="id_form-0-pub_date"></td></tr>

もし、max_num の値が初期データ内に存在するオブジェクトの合計より大きい場合、 extra を上限として空のフォームがフォームセットに追加されます。 フォームの合計の長さは max_num を超えることはできません。例えば、extra=2 と max_num=2、そしてフォームセットが 1 つの initial 項目で初期化される場合、この初期項目のフォームと 1 つの空のフォームが表示されます。

初期データ内の項目数が max_num を超える場合、max_num の値に関わらず全ての初期データのフォームが表示され、追加フォームは 1 つも表示されません。例えば、extra=3 と max_num=1、そしてフォームセットが 2 つの初期項目で初期化される場合、2 つのフォームが初期データとともに表示されます。

max_num の値が None (デフォルト) だった場合、表示されるフォームの上限は大きな数になります (1000)。この数は、実際には制限がないと見なせるでしょう。

デフォルトでは、max_num はいくつのフォームが表示されるかだけに影響し、バリデーションには影響しません。validate_max=True が formset_factory() に渡される場合は、max_num はバリデーションに影響します。validate_max をご覧ください。

Limiting the maximum number of instantiated forms

New in Django 3.2.

The absolute_max parameter to formset_factory() allows limiting the number of forms that can be instantiated when supplying POST data. This protects against memory exhaustion attacks using forged POST requests:

>>> from django.forms.formsets import formset_factory
>>> from myapp.forms import ArticleForm
>>> ArticleFormSet = formset_factory(ArticleForm, absolute_max=1500)
>>> data = {
...     'form-TOTAL_FORMS': '1501',
...     'form-INITIAL_FORMS': '0',
... }
>>> formset = ArticleFormSet(data)
>>> len(formset.forms)
1500
>>> formset.is_valid()
False
>>> formset.non_form_errors()
['Please submit at most 1000 forms.']

When absolute_max is None, it defaults to max_num + 1000. (If max_num is None, it defaults to 2000).

If absolute_max is less than max_num, a ValueError will be raised.

フォームセットのバリデーション

フォームセットのバリデーションは、普通の Form とほぼ同じです。フォームセットにも is_valid メソッドがあり、フォームセット内の全てのフォームを簡単に検証できます。

>>> from django.forms import formset_factory
>>> from myapp.forms import ArticleForm
>>> ArticleFormSet = formset_factory(ArticleForm)
>>> data = {
...     'form-TOTAL_FORMS': '1',
...     'form-INITIAL_FORMS': '0',
... }
>>> formset = ArticleFormSet(data)
>>> formset.is_valid()
True

この例では、フォームセットにデータを渡さなかったので、有効なフォームを返しています。フォームセットは賢くて、データの変更されなかったフォームを無視してくれます。不適切な記事を提供しようとすると、以下のようになります。

>>> data = {
...     'form-TOTAL_FORMS': '2',
...     'form-INITIAL_FORMS': '0',
...     'form-0-title': 'Test',
...     'form-0-pub_date': '1904-06-16',
...     'form-1-title': 'Test',
...     'form-1-pub_date': '', # <-- this date is missing but required
... }
>>> formset = ArticleFormSet(data)
>>> formset.is_valid()
False
>>> formset.errors
[{}, {'pub_date': ['This field is required.']}]

見て分かるように、 formset.errors はリストで、 そのエントリーはフォームセット内のフォームと一致します。 バリデーションは、2 つのフォームそれぞれに働いて、2 つ目の項目にエラーメッセージが表示されています。

通常の Form を使うときとまったく同じように、フォームセットのフォーム内のそれぞれのフィールドは、ブラウザのバリデーションのための maxlength のような HTML 属性を含むことができます。ただし、フォームセットのフォームフィールドは、required 属性を含みません。これは、フォームを追加したり削除するときにバリデーションが正しく働かない可能性があるためです。

BaseFormSet.total_error_count()

フォームセット内にいくつのエラーがあるかを確かめるためには、total_error_count メソッドが使えます。

>>> # Using the previous example
>>> formset.errors
[{}, {'pub_date': ['This field is required.']}]
>>> len(formset.errors)
2
>>> formset.total_error_count()
1

また、フォームに入力されたデータと初期データが異なっているかどうかもチェックできます (たとえば、フォームがデータなしで送信された場合など)。

>>> data = {
...     'form-TOTAL_FORMS': '1',
...     'form-INITIAL_FORMS': '0',
...     'form-0-title': '',
...     'form-0-pub_date': '',
... }
>>> formset = ArticleFormSet(data)
>>> formset.has_changed()
False

ManagementForm を理解する

You may have noticed the additional data (form-TOTAL_FORMS, form-INITIAL_FORMS) that was required in the formset's data above. This data is required for the ManagementForm. This form is used by the formset to manage the collection of forms contained in the formset. If you don't provide this management data, the formset will be invalid:

>>> data = {
...     'form-0-title': 'Test',
...     'form-0-pub_date': '',
... }
>>> formset = ArticleFormSet(data)
>>> formset.is_valid()
False

これは、表示されているフォームインスタンスの数を追跡するために使用されます。 JavaScriptを使用して新しいフォームを追加する場合は、フォームのカウントフィールドもインクリメントする必要があります。 一方、既存のオブジェクトの削除を許可するためにJavaScriptを使用している場合は、POST データに form-#-DELETE を含めることで、削除対象のマークが適切に削除されていることを確認する必要があります。 すべてのフォームがそれにかかわらず POST データに存在することが期待されます。

ManagementFormは、フォームセット自体の属性として使用できます。 テンプレートでフォームセットをレンダリングするときは、{{ my_formset.management_form }} (my_formsetは適切な名前に置き換えます)をレンダリングすることで、すべての管理データを含めることができます。

注釈

As well as the form-TOTAL_FORMS and form-INITIAL_FORMS fields shown in the examples here, the management form also includes form-MIN_NUM_FORMS and form-MAX_NUM_FORMS fields. They are output with the rest of the management form, but only for the convenience of client-side code. These fields are not required and so are not shown in the example POST data.

Changed in Django 3.2:

formset.is_valid() now returns False rather than raising an exception when the management form is missing or has been tampered with.

total_form_count と initial_form_count

BaseFormSet には、ManagementForm、total_form_count、initial_form_count と密接に関わる 2 つのメソッドがあります。

total_form_count は、対象のフィールドセット内のフォームの合計数を返します。initial_form_count は、記入前のフォームセット内のフォームの数を返し、またいくつのフォームが必須なのかを決めるためにも使われます。通常、これらのメソッドをオーバーライドする必要はありませんが、もし必要な場合はメソッドの動作を理解してからオーバーライドしてください。

empty_form

BaseFormSet には追加の属性 empty_form があり、__prefix__ というプレフィックスとともにフォームのインスタンスを返します。これにより、JavaScript で動的にフォームを操作することが容易となります。

error_messages

New in Django 3.2.

The error_messages argument lets you override the default messages that the formset will raise. Pass in a dictionary with keys matching the error messages you want to override. For example, here is the default error message when the management form is missing:

>>> formset = ArticleFormSet({})
>>> formset.is_valid()
False
>>> formset.non_form_errors()
['ManagementForm data is missing or has been tampered with. Missing fields: form-TOTAL_FORMS, form-INITIAL_FORMS. You may need to file a bug report if the issue persists.']

And here is a custom error message:

>>> formset = ArticleFormSet({}, error_messages={'missing_management_form': 'Sorry, something went wrong.'})
>>> formset.is_valid()
False
>>> formset.non_form_errors()
['Sorry, something went wrong.']

カスタムフォームセットのバリデーション

フォームセットには、Form クラスと同じような clean メソッドがあります。フォームセットのレベルで検証するためのバリデーションは、ここに記述します:

>>> from django.core.exceptions import ValidationError
>>> from django.forms import BaseFormSet
>>> from django.forms import formset_factory
>>> from myapp.forms import ArticleForm

>>> class BaseArticleFormSet(BaseFormSet):
...     def clean(self):
...         """Checks that no two articles have the same title."""
...         if any(self.errors):
...             # Don't bother validating the formset unless each form is valid on its own
...             return
...         titles = []
...         for form in self.forms:
...             if self.can_delete and self._should_delete_form(form):
...                 continue
...             title = form.cleaned_data.get('title')
...             if title in titles:
...                 raise ValidationError("Articles in a set must have distinct titles.")
...             titles.append(title)

>>> ArticleFormSet = formset_factory(ArticleForm, formset=BaseArticleFormSet)
>>> data = {
...     'form-TOTAL_FORMS': '2',
...     'form-INITIAL_FORMS': '0',
...     'form-0-title': 'Test',
...     'form-0-pub_date': '1904-06-16',
...     'form-1-title': 'Test',
...     'form-1-pub_date': '1912-06-23',
... }
>>> formset = ArticleFormSet(data)
>>> formset.is_valid()
False
>>> formset.errors
[{}, {}]
>>> formset.non_form_errors()
['Articles in a set must have distinct titles.']

フォームセットの clean メソッドは、Form.clean メソッドが呼ばれた後に呼び出されます。エラーを取得するには、フォームセットの non_form_errors() メソッドを使います。

Non-form errors will be rendered with an additional class of nonform to help distinguish them from form-specific errors. For example, {{ formset.non_form_errors }} would look like:

<ul class="errorlist nonform">
    <li>Articles in a set must have distinct titles.</li>
</ul>

Changed in Django 4.0:

The additional nonform class was added.

フォームセット内のフォームの数を検証する

送信されたフォームの最小および最大数を検証するために、Django にはいくつかの方法が用意されています。フォームの数のバリデーションをさらにカスタマイズする必要があるときは、カスタムのフォームセットバリデーションを使用する必要があります。

validate_max

If validate_max=True is passed to formset_factory(), validation will also check that the number of forms in the data set, minus those marked for deletion, is less than or equal to max_num.

>>> from django.forms import formset_factory
>>> from myapp.forms import ArticleForm
>>> ArticleFormSet = formset_factory(ArticleForm, max_num=1, validate_max=True)
>>> data = {
...     'form-TOTAL_FORMS': '2',
...     'form-INITIAL_FORMS': '0',
...     'form-0-title': 'Test',
...     'form-0-pub_date': '1904-06-16',
...     'form-1-title': 'Test 2',
...     'form-1-pub_date': '1912-06-23',
... }
>>> formset = ArticleFormSet(data)
>>> formset.is_valid()
False
>>> formset.errors
[{}, {}]
>>> formset.non_form_errors()
['Please submit at most 1 form.']

validate_max=True validates against max_num strictly even if max_num was exceeded because the amount of initial data supplied was excessive.

注釈

Regardless of validate_max, if the number of forms in a data set exceeds absolute_max, then the form will fail to validate as if validate_max were set, and additionally only the first absolute_max forms will be validated. The remainder will be truncated entirely. This is to protect against memory exhaustion attacks using forged POST requests. See Limiting the maximum number of instantiated forms.

validate_min

If validate_min=True is passed to formset_factory(), validation will also check that the number of forms in the data set, minus those marked for deletion, is greater than or equal to min_num.

>>> from django.forms import formset_factory
>>> from myapp.forms import ArticleForm
>>> ArticleFormSet = formset_factory(ArticleForm, min_num=3, validate_min=True)
>>> data = {
...     'form-TOTAL_FORMS': '2',
...     'form-INITIAL_FORMS': '0',
...     'form-0-title': 'Test',
...     'form-0-pub_date': '1904-06-16',
...     'form-1-title': 'Test 2',
...     'form-1-pub_date': '1912-06-23',
... }
>>> formset = ArticleFormSet(data)
>>> formset.is_valid()
False
>>> formset.errors
[{}, {}]
>>> formset.non_form_errors()
['Please submit at least 3 forms.']

注釈

Regardless of validate_min, if a formset contains no data, then extra + min_num empty forms will be displayed.

Dealing with ordering and deletion of forms

formset_factory() には、フォームセット内のフォームの順序およびフォームセットからのフォームの削除に役立つ 2 つのオプション引数があります。

can_order

BaseFormSet.can_order

デフォルト値: False

並び替えができるフォームセットを作成できるようにします:

>>> from django.forms import formset_factory
>>> from myapp.forms import ArticleForm
>>> ArticleFormSet = formset_factory(ArticleForm, can_order=True)
>>> formset = ArticleFormSet(initial=[
...     {'title': 'Article #1', 'pub_date': datetime.date(2008, 5, 10)},
...     {'title': 'Article #2', 'pub_date': datetime.date(2008, 5, 11)},
... ])
>>> for form in formset:
...     print(form.as_table())
<tr><th><label for="id_form-0-title">Title:</label></th><td><input type="text" name="form-0-title" value="Article #1" id="id_form-0-title"></td></tr>
<tr><th><label for="id_form-0-pub_date">Pub date:</label></th><td><input type="text" name="form-0-pub_date" value="2008-05-10" id="id_form-0-pub_date"></td></tr>
<tr><th><label for="id_form-0-ORDER">Order:</label></th><td><input type="number" name="form-0-ORDER" value="1" id="id_form-0-ORDER"></td></tr>
<tr><th><label for="id_form-1-title">Title:</label></th><td><input type="text" name="form-1-title" value="Article #2" id="id_form-1-title"></td></tr>
<tr><th><label for="id_form-1-pub_date">Pub date:</label></th><td><input type="text" name="form-1-pub_date" value="2008-05-11" id="id_form-1-pub_date"></td></tr>
<tr><th><label for="id_form-1-ORDER">Order:</label></th><td><input type="number" name="form-1-ORDER" value="2" id="id_form-1-ORDER"></td></tr>
<tr><th><label for="id_form-2-title">Title:</label></th><td><input type="text" name="form-2-title" id="id_form-2-title"></td></tr>
<tr><th><label for="id_form-2-pub_date">Pub date:</label></th><td><input type="text" name="form-2-pub_date" id="id_form-2-pub_date"></td></tr>
<tr><th><label for="id_form-2-ORDER">Order:</label></th><td><input type="number" name="form-2-ORDER" id="id_form-2-ORDER"></td></tr>

各フィールドに追加フィールドが与えられます。この新しいフィールドは ORDER という名前の forms.IntegerField です。初期データから来たフォームに対しては、自動的に数値が与えられます。ユーザーがこれらの値を変更した際に何が起きるかを見てみましょう:

>>> data = {
...     'form-TOTAL_FORMS': '3',
...     'form-INITIAL_FORMS': '2',
...     'form-0-title': 'Article #1',
...     'form-0-pub_date': '2008-05-10',
...     'form-0-ORDER': '2',
...     'form-1-title': 'Article #2',
...     'form-1-pub_date': '2008-05-11',
...     'form-1-ORDER': '1',
...     'form-2-title': 'Article #3',
...     'form-2-pub_date': '2008-05-01',
...     'form-2-ORDER': '0',
... }

>>> formset = ArticleFormSet(data, initial=[
...     {'title': 'Article #1', 'pub_date': datetime.date(2008, 5, 10)},
...     {'title': 'Article #2', 'pub_date': datetime.date(2008, 5, 11)},
... ])
>>> formset.is_valid()
True
>>> for form in formset.ordered_forms:
...     print(form.cleaned_data)
{'pub_date': datetime.date(2008, 5, 1), 'ORDER': 0, 'title': 'Article #3'}
{'pub_date': datetime.date(2008, 5, 11), 'ORDER': 1, 'title': 'Article #2'}
{'pub_date': datetime.date(2008, 5, 10), 'ORDER': 2, 'title': 'Article #1'}

BaseFormSet also provides an ordering_widget attribute and get_ordering_widget() method that control the widget used with can_order.

ordering_widget

BaseFormSet.ordering_widget

Default: NumberInput

Set ordering_widget to specify the widget class to be used with can_order:

>>> from django.forms import BaseFormSet, formset_factory
>>> from myapp.forms import ArticleForm
>>> class BaseArticleFormSet(BaseFormSet):
...     ordering_widget = HiddenInput

>>> ArticleFormSet = formset_factory(ArticleForm, formset=BaseArticleFormSet, can_order=True)

get_ordering_widget

BaseFormSet.get_ordering_widget()

Override get_ordering_widget() if you need to provide a widget instance for use with can_order:

>>> from django.forms import BaseFormSet, formset_factory
>>> from myapp.forms import ArticleForm
>>> class BaseArticleFormSet(BaseFormSet):
...     def get_ordering_widget(self):
...         return HiddenInput(attrs={'class': 'ordering'})

>>> ArticleFormSet = formset_factory(ArticleForm, formset=BaseArticleFormSet, can_order=True)

can_delete

BaseFormSet.can_delete

デフォルト値: False

削除対象のフォームを選択できるフォームセットを作成できるようにします:

>>> from django.forms import formset_factory
>>> from myapp.forms import ArticleForm
>>> ArticleFormSet = formset_factory(ArticleForm, can_delete=True)
>>> formset = ArticleFormSet(initial=[
...     {'title': 'Article #1', 'pub_date': datetime.date(2008, 5, 10)},
...     {'title': 'Article #2', 'pub_date': datetime.date(2008, 5, 11)},
... ])
>>> for form in formset:
...     print(form.as_table())
<tr><th><label for="id_form-0-title">Title:</label></th><td><input type="text" name="form-0-title" value="Article #1" id="id_form-0-title"></td></tr>
<tr><th><label for="id_form-0-pub_date">Pub date:</label></th><td><input type="text" name="form-0-pub_date" value="2008-05-10" id="id_form-0-pub_date"></td></tr>
<tr><th><label for="id_form-0-DELETE">Delete:</label></th><td><input type="checkbox" name="form-0-DELETE" id="id_form-0-DELETE"></td></tr>
<tr><th><label for="id_form-1-title">Title:</label></th><td><input type="text" name="form-1-title" value="Article #2" id="id_form-1-title"></td></tr>
<tr><th><label for="id_form-1-pub_date">Pub date:</label></th><td><input type="text" name="form-1-pub_date" value="2008-05-11" id="id_form-1-pub_date"></td></tr>
<tr><th><label for="id_form-1-DELETE">Delete:</label></th><td><input type="checkbox" name="form-1-DELETE" id="id_form-1-DELETE"></td></tr>
<tr><th><label for="id_form-2-title">Title:</label></th><td><input type="text" name="form-2-title" id="id_form-2-title"></td></tr>
<tr><th><label for="id_form-2-pub_date">Pub date:</label></th><td><input type="text" name="form-2-pub_date" id="id_form-2-pub_date"></td></tr>
<tr><th><label for="id_form-2-DELETE">Delete:</label></th><td><input type="checkbox" name="form-2-DELETE" id="id_form-2-DELETE"></td></tr>

Similar to can_order this adds a new field to each form named DELETE and is a forms.BooleanField. When data comes through marking any of the delete fields you can access them with deleted_forms:

>>> data = {
...     'form-TOTAL_FORMS': '3',
...     'form-INITIAL_FORMS': '2',
...     'form-0-title': 'Article #1',
...     'form-0-pub_date': '2008-05-10',
...     'form-0-DELETE': 'on',
...     'form-1-title': 'Article #2',
...     'form-1-pub_date': '2008-05-11',
...     'form-1-DELETE': '',
...     'form-2-title': '',
...     'form-2-pub_date': '',
...     'form-2-DELETE': '',
... }

>>> formset = ArticleFormSet(data, initial=[
...     {'title': 'Article #1', 'pub_date': datetime.date(2008, 5, 10)},
...     {'title': 'Article #2', 'pub_date': datetime.date(2008, 5, 11)},
... ])
>>> [form.cleaned_data for form in formset.deleted_forms]
[{'DELETE': True, 'pub_date': datetime.date(2008, 5, 10), 'title': 'Article #1'}]

If you are using a ModelFormSet, model instances for deleted forms will be deleted when you call formset.save().

If you call formset.save(commit=False), objects will not be deleted automatically. You'll need to call delete() on each of the formset.deleted_objects to actually delete them:

>>> instances = formset.save(commit=False)
>>> for obj in formset.deleted_objects:
...     obj.delete()

On the other hand, if you are using a plain FormSet, it's up to you to handle formset.deleted_forms, perhaps in your formset's save() method, as there's no general notion of what it means to delete a form.

BaseFormSet also provides a deletion_widget attribute and get_deletion_widget() method that control the widget used with can_delete.

deletion_widget

New in Django 4.0.

BaseFormSet.deletion_widget

Default: CheckboxInput

Set deletion_widget to specify the widget class to be used with can_delete:

>>> from django.forms import BaseFormSet, formset_factory
>>> from myapp.forms import ArticleForm
>>> class BaseArticleFormSet(BaseFormSet):
...     deletion_widget = HiddenInput

>>> ArticleFormSet = formset_factory(ArticleForm, formset=BaseArticleFormSet, can_delete=True)

get_deletion_widget

New in Django 4.0.

BaseFormSet.get_deletion_widget()

Override get_deletion_widget() if you need to provide a widget instance for use with can_delete:

>>> from django.forms import BaseFormSet, formset_factory
>>> from myapp.forms import ArticleForm
>>> class BaseArticleFormSet(BaseFormSet):
...     def get_deletion_widget(self):
...         return HiddenInput(attrs={'class': 'deletion'})

>>> ArticleFormSet = formset_factory(ArticleForm, formset=BaseArticleFormSet, can_delete=True)

can_delete_extra

New in Django 3.2.

BaseFormSet.can_delete_extra

デフォルト値: True

While setting can_delete=True, specifying can_delete_extra=False will remove the option to delete extra forms.

Adding additional fields to a formset

If you need to add additional fields to the formset this can be easily accomplished. The formset base class provides an add_fields method. You can override this method to add your own fields or even redefine the default fields/attributes of the order and deletion fields:

>>> from django.forms import BaseFormSet
>>> from django.forms import formset_factory
>>> from myapp.forms import ArticleForm
>>> class BaseArticleFormSet(BaseFormSet):
...     def add_fields(self, form, index):
...         super().add_fields(form, index)
...         form.fields["my_field"] = forms.CharField()

>>> ArticleFormSet = formset_factory(ArticleForm, formset=BaseArticleFormSet)
>>> formset = ArticleFormSet()
>>> for form in formset:
...     print(form.as_table())
<tr><th><label for="id_form-0-title">Title:</label></th><td><input type="text" name="form-0-title" id="id_form-0-title"></td></tr>
<tr><th><label for="id_form-0-pub_date">Pub date:</label></th><td><input type="text" name="form-0-pub_date" id="id_form-0-pub_date"></td></tr>
<tr><th><label for="id_form-0-my_field">My field:</label></th><td><input type="text" name="form-0-my_field" id="id_form-0-my_field"></td></tr>

Passing custom parameters to formset forms

Sometimes your form class takes custom parameters, like MyArticleForm. You can pass this parameter when instantiating the formset:

>>> from django.forms import BaseFormSet
>>> from django.forms import formset_factory
>>> from myapp.forms import ArticleForm

>>> class MyArticleForm(ArticleForm):
...     def __init__(self, *args, user, **kwargs):
...         self.user = user
...         super().__init__(*args, **kwargs)

>>> ArticleFormSet = formset_factory(MyArticleForm)
>>> formset = ArticleFormSet(form_kwargs={'user': request.user})

The form_kwargs may also depend on the specific form instance. The formset base class provides a get_form_kwargs method. The method takes a single argument - the index of the form in the formset. The index is None for the empty_form:

>>> from django.forms import BaseFormSet
>>> from django.forms import formset_factory

>>> class BaseArticleFormSet(BaseFormSet):
...     def get_form_kwargs(self, index):
...         kwargs = super().get_form_kwargs(index)
...         kwargs['custom_kwarg'] = index
...         return kwargs

Customizing a formset's prefix

In the rendered HTML, formsets include a prefix on each field's name. By default, the prefix is 'form', but it can be customized using the formset's prefix argument.

For example, in the default case, you might see:

<label for="id_form-0-title">Title:</label>
<input type="text" name="form-0-title" id="id_form-0-title">

But with ArticleFormset(prefix='article') that becomes:

<label for="id_article-0-title">Title:</label>
<input type="text" name="article-0-title" id="id_article-0-title">

This is useful if you want to use more than one formset in a view.

Using a formset in views and templates

Formsets have five attributes and five methods associated with rendering.

BaseFormSet.renderer

New in Django 4.0.

Specifies the renderer to use for the formset. Defaults to the renderer specified by the FORM_RENDERER setting.

BaseFormSet.template_name

New in Django 4.0.

The name of the template used when calling __str__ or render(). This template renders the formset's management form and then each form in the formset as per the template defined by the form's template_name. This is a proxy of as_table by default.

BaseFormSet.template_name_p

New in Django 4.0.

The name of the template used when calling as_p(). By default this is 'django/forms/formsets/p.html'. This template renders the formset's management form and then each form in the formset as per the form's as_p() method.

BaseFormSet.template_name_table

New in Django 4.0.

The name of the template used when calling as_table(). By default this is 'django/forms/formsets/table.html'. This template renders the formset's management form and then each form in the formset as per the form's as_table() method.

BaseFormSet.template_name_ul

New in Django 4.0.

The name of the template used when calling as_ul(). By default this is 'django/forms/formsets/ul.html'. This template renders the formset's management form and then each form in the formset as per the form's as_ul() method.

BaseFormSet.get_context()

New in Django 4.0.

Returns the context for rendering a formset in a template.

The available context is:

• formset : The instance of the formset.

BaseFormSet.render(template_name=None, context=None, renderer=None)

New in Django 4.0.

The render method is called by __str__ as well as the as_p(), as_ul(), and as_table() methods. All arguments are optional and will default to:

• template_name: template_name
• context: Value returned by get_context()
• renderer: Value returned by renderer

BaseFormSet.as_p()

Renders the formset with the template_name_p template.

BaseFormSet.as_table()

Renders the formset with the template_name_table template.

BaseFormSet.as_ul()

Renders the formset with the template_name_ul template.

Using a formset inside a view is not very different from using a regular Form class. The only thing you will want to be aware of is making sure to use the management form inside the template. Let's look at a sample view:

from django.forms import formset_factory
from django.shortcuts import render
from myapp.forms import ArticleForm

def manage_articles(request):
    ArticleFormSet = formset_factory(ArticleForm)
    if request.method == 'POST':
        formset = ArticleFormSet(request.POST, request.FILES)
        if formset.is_valid():
            # do something with the formset.cleaned_data
            pass
    else:
        formset = ArticleFormSet()
    return render(request, 'manage_articles.html', {'formset': formset})

The manage_articles.html template might look like this:

<form method="post">
    {{ formset.management_form }}
    <table>
        {% for form in formset %}
        {{ form }}
        {% endfor %}
    </table>
</form>

However there's a slight shortcut for the above by letting the formset itself deal with the management form:

<form method="post">
    <table>
        {{ formset }}
    </table>
</form>

The above ends up calling the BaseFormSet.render() method on the formset class. This renders the formset using the template specified by the template_name attribute. Similar to forms, by default the formset will be rendered as_table, with other helper methods of as_p and as_ul being available. The rendering of the formset can be customized by specifying the template_name attribute, or more generally by overriding the default template.

Changed in Django 4.0:

Rendering of formsets was moved to the template engine.

Manually rendered can_delete and can_order

If you manually render fields in the template, you can render can_delete parameter with {{ form.DELETE }}:

<form method="post">
    {{ formset.management_form }}
    {% for form in formset %}
        <ul>
            <li>{{ form.title }}</li>
            <li>{{ form.pub_date }}</li>
            {% if formset.can_delete %}
                <li>{{ form.DELETE }}</li>
            {% endif %}
        </ul>
    {% endfor %}
</form>

Similarly, if the formset has the ability to order (can_order=True), it is possible to render it with {{ form.ORDER }}.

Using more than one formset in a view

You are able to use more than one formset in a view if you like. Formsets borrow much of its behavior from forms. With that said you are able to use prefix to prefix formset form field names with a given value to allow more than one formset to be sent to a view without name clashing. Let's take a look at how this might be accomplished:

from django.forms import formset_factory
from django.shortcuts import render
from myapp.forms import ArticleForm, BookForm

def manage_articles(request):
    ArticleFormSet = formset_factory(ArticleForm)
    BookFormSet = formset_factory(BookForm)
    if request.method == 'POST':
        article_formset = ArticleFormSet(request.POST, request.FILES, prefix='articles')
        book_formset = BookFormSet(request.POST, request.FILES, prefix='books')
        if article_formset.is_valid() and book_formset.is_valid():
            # do something with the cleaned_data on the formsets.
            pass
    else:
        article_formset = ArticleFormSet(prefix='articles')
        book_formset = BookFormSet(prefix='books')
    return render(request, 'manage_articles.html', {
        'article_formset': article_formset,
        'book_formset': book_formset,
    })

You would then render the formsets as normal. It is important to point out that you need to pass prefix on both the POST and non-POST cases so that it is rendered and processed correctly.

Each formset's prefix replaces the default form prefix that's added to each field's name and id HTML attributes.

Last update:

2022年6月01日

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