inlineformset_factory create new objects and edit

Question

In the django docs, there's an example of using inlineformset_factory to edit already created objects

https://docs.djangoproject.com/en/dev/topics/forms/modelforms/#using-an-inline-formset-in-a-view

I changed the example to be this way:

def manage_books(request):
    author = Author()
    BookInlineFormSet = inlineformset_factory(Author, Book, fields=('title',))
    if request.method == "POST":
        formset = BookInlineFormSet(request.POST, request.FILES, instance=author)
        if formset.is_valid():
            formset.save()
            return HttpResponseRedirect(author.get_absolute_url())
    else:
        formset = BookInlineFormSet(instance=author)
    return render_to_response("manage_books.html", {
        "formset": formset,
    })

With the above, it renders only the inline model without the parent model.

To create a new object, say Author, with multiple Books associated to, using inlineformset_factory, what's the approach?

An example using the above Author Book model from django docs will be helpful. The django docs only provided example of how to edit already created object using inlineformset_factory but not to create new one

Answer 1

I am posting my final solutions, as per extensive assistant given by Onyeka.

Below I post the Add and Edit solutions of using inlineformset_factory of Django using the Author and Book example found in the Django Docs.

First, the Adding of Author object, with 3 extras of Book object to be appended.

Obviously, this goes into your views.py

def add_author(request):
    '''This function creates a brand new Author object with related Book objects using inlineformset_factory'''
    author = Author()
    author_form = AuthorModelForm(instance=author) # setup a form for the parent
BookInlineFormSet = inlineformset_factory(Author, Book, fields=('title',))

if request.method == "POST":
    author_form = AuthorModelForm(request.POST)
    formset = BookInlineFormSet(request.POST, request.FILES)

    if author_form.is_valid():
        created_author = author_form.save(commit=False)
        formset = BookInlineFormSet(request.POST, request.FILES, instance=created_author)

        if formset.is_valid():
            created_author.save()
            formset.save()
            return HttpResponseRedirect(created_author.get_absolute_url())
else:
    author_form = AuthorModelForm(instance=author)
    formset = BookInlineFormSet()

return render(request, "add_author.html", {
    "author_form": author_form,
    "formset": formset,
})


def edit_author(request, author_id):
    '''This function edits an Author object and its related Book objects using inlineformset_factory'''
    if id:
        author = Author.objects.get(pk=author_id)  # if this is an edit form, replace the author instance with the existing one
    else:
        author = Author()
    author_form = AuthorModelForm(instance=author) # setup a form for the parent
BookInlineFormSet = inlineformset_factory(Author, Book, fields=('title',))
formset = BookInlineFormSet(instance=author)

if request.method == "POST":
    author_form = AuthorModelForm(request.POST)

    if id:
        author_form = AuthorModelForm(request.POST, instance=author)

    formset = BookInlineFormSet(request.POST, request.FILES)

    if author_form.is_valid():
        created_author = author_form.save(commit=False)
        formset = BookInlineFormSet(request.POST, request.FILES, instance=created_author)

        if formset.is_valid():
            created_author.save()
            formset.save()
            return HttpResponseRedirect(created_author.get_absolute_url())

return render(request, "edit_author.html", {
    "author_id": author_id, # This author_id is referenced 
                            # in template for constructing the posting url via {% url %} tag
    "author_form": author_form,
    "formset": formset,
})

This part goes into your urls.py, assuming views have been imported, and urlpatterns constructed already.

...
    url(r'^add/book/$', views.add_author, name='add_author'),
    url(r'^edit/(?P<author_id>[\d]+)$', views.edit_author, name='edit_author'),
...

Now to the templates part. The edit Author object template (edit_author.html) looks like this (no styling applied)

<form action="{% url 'edit_book' author_id %}" method="POST" >
<!-- See above: We're using the author_id that was passed to template via views render of the edit_author(...) function -->
{% csrf_token %} <!-- You're dealing with forms. csrf_token must come -->
{{ author_form.as_p }}
{{ formset.as_p }}
<input type="submit" value="submit">
</form>

To add a brand new Author object via template (add_author.html):

<form action="." method="POST" >{% csrf_token %}
{{ author_form.as_p }}
{{ formset.as_p }}
<input type="submit" value="submit">
</form>

NOTE:

Using the action='.' might appear to be a cheap way of constructing the url, whereby the form posts the form data to the same page. With this example, using the action='.' for the edit_author.html template always got the form posted to /edit/ instead of /edit/1 or /edit/2

Constructing the url using the {% url 'edit_author' author_id %} ensures the form always posts to the right url. Failing to do use the {% url %} cost me lots of hours and trouble.

Big thanks to Onyeka.

Answer 2

I've done that using Django Class-Based Views.

Here's my approach:

models.py

from django.db import models

class Author(models.Model):
    name = models.CharField(max_length=100)


class Book(models.Model):
    author = models.ForeignKey(Author)
    title = models.CharField(max_length=100)

forms.py

from django.forms import ModelForm
from django.forms.models import inlineformset_factory

from crispy_forms.helper import FormHelper
from crispy_forms.layout import Layout, Fieldset

from .models import Author, Book

class AuthorForm(ModelForm):
    class Meta:
        model = Author
        fields = ('name', )

    @property
    def helper(self):
        helper = FormHelper()
        helper.form_tag = False # This is crucial.

        helper.layout = Layout(
            Fieldset('Create new author', 'name'),
        )

        return helper


class BookFormHelper(FormHelper):
    def __init__(self, *args, **kwargs):
        super(BookFormHelper, self).__init__(*args, **kwargs)
        self.form_tag = False
        self.layout = Layout(
            Fieldset("Add author's book", 'title'),
        )


BookFormset = inlineformset_factory(
    Author,
    Book,
    fields=('title', ),
    extra=2,
    can_delete=False,
)

views.py

from django.views.generic import CreateView
from django.http import HttpResponseRedirect

from .forms import AuthorForm, BookFormset, BookFormHelper
from .models import Book, Author

class AuthorCreateView(CreateView):
    form_class = AuthorForm
    template_name = 'library/manage_books.html'
    model = Author
    success_url = '/'

    def get(self, request, *args, **kwargs):
        self.object = None
        form_class = self.get_form_class()
        form = self.get_form(form_class)
        book_form = BookFormset()
        book_formhelper = BookFormHelper()

        return self.render_to_response(
            self.get_context_data(form=form, book_form=book_form)
        )

    def post(self, request, *args, **kwargs):
        self.object = None
        form_class = self.get_form_class()
        form = self.get_form(form_class)
        book_form = BookFormset(self.request.POST)

        if (form.is_valid() and book_form.is_valid()):
            return self.form_valid(form, book_form)

        return self.form_invalid(form, book_form)

    def form_valid(self, form, book_form):
        """
        Called if all forms are valid. Creates a Author instance along
        with associated books and then redirects to a success page.
        """
        self.object = form.save()
        book_form.instance = self.object
        book_form.save()

        return HttpResponseRedirect(self.get_success_url())

    def form_invalid(self, form, book_form):
        """
        Called if whether a form is invalid. Re-renders the context
        data with the data-filled forms and errors.
        """
        return self.render_to_response(
            self.get_context_data(form=form, book_form=book_form)
        )

    def get_context_data(self, **kwargs):
        """ Add formset and formhelper to the context_data. """
        ctx = super(AuthorCreateView, self).get_context_data(**kwargs)
        book_formhelper = BookFormHelper()

        if self.request.POST:
            ctx['form'] = AuthorForm(self.request.POST)
            ctx['book_form'] = BookFormset(self.request.POST)
            ctx['book_formhelper'] = book_formhelper
        else:
            ctx['form'] = AuthorForm()
            ctx['book_form'] = BookFormset()
            ctx['book_formhelper'] = book_formhelper

        return ctx

urls.py

from django.conf.urls import patterns, url
from django.views.generic import TemplateView

from library.views import AuthorCreateView

urlpatterns = patterns('',
    url(r'^author/manage$', AuthorCreateView.as_view(), name='handle-books'),
    url(r'^$', TemplateView.as_view(template_name='home.html'), name='home'),
)

manage_books.html

{% load crispy_forms_tags %}

<head>
  <!-- Latest compiled and minified CSS -->
  <link rel="stylesheet"
    href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css">
</head>

<div class='container'>
  <form method='post'>
    {% crispy form %}
    {{ book_form.management_form }}
    {{ book_form.non_form_errors }}

    {% crispy book_form book_formhelper %}
    <input class='btn btn-primary' type='submit' value='Save'>
  </form>
<div>

Notice:

• This is a simple runable example that use the inlineformset_factory feature and Django generic Class-Based Views
• I'm assumming django-crispy-forms is installed, and it's properly configured.
• Code repository is hosted at: https://bitbucket.org/slackmart/library_example

I know it's more code that the showed solutions, but start to using Django Class-Based Views is great.

Answer 3

i did exactly what you are trying : https://github.com/yakoub/django_training/tree/master/article

you need to create a separate form using the prefix attribute . then when you save you need to iterate over all books and associate them with the author you just created .

Answer 4

I didn't read your question properly at first. You need to also render the the form for the parent model. I haven't tested this, I'm going off what I've done before and the previously linked answer, but it should work.

UPDATE

If you're using the view to both and edit, you should check for an Author ID first. If there's no ID, it'll render both forms as a new instance, whereas with an ID it'll, fill them with the existing data. Then you can check if there was a POST request.

def manage_books(request, id):

    if id:
        author = Author.objects.get(pk=author_id)  # if this is an edit form, replace the author instance with the existing one
    else: 
        author = Author()
    author_form = AuthorModelForm(instance=author) # setup a form for the parent

    BookInlineFormSet = inlineformset_factory(Author, Book, fields=('title',))
    formset = BookInlineFormSet(instance=author)

    if request.method == "POST":
        author_form = AuthorModelForm(request.POST)

        if id: 
            author_form = AuthorModelForm(request.POST, instance=author)

        formset = BookInlineFormSet(request.POST, request.FILES)

        if author_form.is_valid():
            created_author = author_form.save(commit=False)
            formset = BookInlineFormSet(request.POST, request.FILES, instance=created_author)

            if formset.is_valid():
                created_author.save()
                formset.save()
                return HttpResponseRedirect(created_author.get_absolute_url())

    return render_to_response("manage_books.html", {
        "author_form": author_form,
        "formset": formset,
    })