Django model formset example

django_model_formset.py

from django.forms.models import inlineformset_factory
from django.shortcuts import render
from django.http import HttpResponseRedirect

from django import forms

from crispy_forms.helper import FormHelper


# The forms ---------------------------------------------------------------------------------------------------------
class ParentForm(forms.ModelForm):
    # For crispy
    helper = FormHelper()
    helper.form_class = 'form-horizontal'
    helper.label_class = 'col-md-2'
    helper.field_class = 'col-md-10'
    helper.include_media = False
    helper.form_tag = False

    class Meta:
        model = models.Parent
        fields = ('field1', 'field2')
        
        
class ItemForm(forms.ModelForm):
    class Meta:
        model = models.Item
        fields = ('field1', 'field2')


class BaseItemFormSet(forms.models.BaseInlineFormSet):
    """
    Use this to do cross form validation. This is commonly needed. Although sometimes a better solution is to
    use model constraints such as "unique_together"
    """
    def clean(self):
        super(BaseItemFormSet, self).clean()

        if any(self.errors):
            # Don't bother validating the formset unless each form is valid on its own
            return

        # Do error cross form checking here
        for form in self.forms:
            if error:
                raise forms.ValidationError("Opps. There was an error")


# For using django crispy
class ItemFormSetFormHelper(FormHelper):
    def __init__(self, *args, **kwargs):
        super(ItemFormSetFormHelper, self).__init__(*args, **kwargs)
        self.template = 'bootstrap/table_inline_formset.html'
        self.include_media = False
        self.form_tag = False
        self.form_show_errors = True


# The view ----------------------------------------------------------------------------------------------------------
def model_w_items_view(request, parent_id=None):
    if parent_id:
        parent_instance = models.Parent.objects.get(id=int(parent_id))
        headline = 'Update'
        extra_lines = 1
    else:
        parent_instance = None
        headline = 'Create'
        extra_lines = 5

    # fk_name = the name of the foreign key field in models.Item
    ItemFormSet = inlineformset_factory(
        models.Parent, models.Item, form=ItemForm, formset=BaseItemFormSet,
        fk_name='parent', extra=int(extra_lines)
    )

    # Use this if you are using crispy to layout the Item forms
    formset_helper = ItemFormSetFormHelper()

    if request.method == "POST":
        main_form = ItemForm(request.POST, instance=parent_instance)
        if main_form.is_valid():
            parent_instance = main_form.save()

        formset = ItemFormSet(request.POST, request.FILES, instance=parent_instance)
        if main_form.is_valid() and formset.is_valid():
            main_form.save()
            formset.save()
            return HttpResponseRedirect('/')
    else:
        formset = ItemFormSet(instance=parent_instance)
        main_form = ParentForm(instance=parent_instance)

    return render(request, "my_template.html", {
        'main_form': main_form,
        'item_formset': formset,
        'formset_helper': formset_helper,
        'parent_instance': parent_instance,
        'headline': headline,
    })

# The template ------------------------------------------------------------------------------------------------------
# This template uses Bootstrap panels
'''
{% load crispy_forms_tags %}

<div class="panel panel-default">
    <div class="panel-heading">
        <h4 class="panel-heading">{{ headline }}</h4>
    </div>

    <div class="panel-body">
        <form class="form-horizontal" method="post">
            {% if main_form.non_form_errors %}
                {{ main_form.non_form_errors }}
            {% endif %}

            {% crispy main_form %}

            {% if item_formset.non_form_errors %}
                {{ item_formset.non_form_errors }}
            {% endif %}

            {% crispy item_formset helper %}

            <div>
                <input type="submit" name="save" value="Save" class="btn btn-primary">
                <a onclick='window.history.back();' class="btn btn-default">Cancel</a>
            </div>
        </form>
    </div>
</div>
'''