Crispy Form VariableDoesNotExist on Django

Question

For crispy form on Django, I keep getting VariableDoesNotExist at / Failed lookup for key [form] in u'[{\'False\': False, \'None\': None,.....

{% extends 'base.html' %}
{% load crispy_forms_tags %}

{% block loginForm %}
    <div class="container" style="padding-bottom: 70px;">
        <div class='row'>
            <div class='col-md-6 col-md-offset-3'>
                <div class="well">
                    <legend>Sign in</legend>
                    <form method="post" action="{% url 'django.contrib.auth.views.login' %}" class="form-horizontal">
                        {% crispy form %}
                        <input type="hidden" name="next" value="{{ next }}"/>
                    </form>
                </div>
            </div>
        </div>
    </div>

{% endblock loginForm %}

forms.py:

from django import forms
from crispy_forms.helper import FormHelper
from crispy_forms.layout import Layout, Div, Submit, HTML, Button, Row, Field, Hidden, Fieldset
from crispy_forms.bootstrap import AppendedText, PrependedText, FormActions
from django.contrib.auth.forms import AuthenticationForm


class LoginForm(AuthenticationForm):
    def __init__(self, *args, **kwargs):
        super(LoginForm, self).__init__(*args, **kwargs)
        self.helper = FormHelper()
        self.helper.form_class = 'form-horizontal'
        self.helper.label_class = 'col-lg-2'
        self.helper.field_class = 'col-lg-8'
        self.helper.form_tag = False
        self.helper.layout = Layout(
            Field('username', placeholder="username", css_class='input-xlarge'),
            Field('password', placeholder="Password", css_class='input-xlarge'),
            FormActions(
                Submit('login', 'Login', css_class="btn-primary"),
            )
        )

I don't understand, because according to documentation I am using FormHelper on attribute helper so I should be able to use {% crispy form %}

Answer 1

The first argument to the crispy template tag is the name of the context variable where Crispy Forms expects the Form instance. So you need to somehow get a Form instance in your template context. If you were using this form in a view, you could do something like

def yourview(request):
    return TemplateResponse(request, "yourtemplate.html", {'form': LoginForm()})

If you want to have that form on many different pages, I'd suggest an inclusion tag:

@register.inclusion_tag('path/to/login_form.html')
def display_login_form():
    return {'form': LoginForm()}

And in your template:

{% load your_template_tags %}
{% display_login_form %}

(see also the usual setup procedure for custom template tags)

Answer 2

I came across the VariableDoesNotExist problem as well with Failed lookup for key [form], but for me the problem was that I mistakenly used generic.DetailView as base class instead of generic.UpdateView.

Changing to UpdateView fixed the problem.

class MyUpdateView(generic.UpdateView):

    template_name = "object_update.html"
    model = MyModel
    form_class = MyCreateForm