{% crispy %} tag with forms

django-crispy-forms implements a class called FormHelper that defines the form rendering behavior. Helpers give you a way to control form attributes and its layout, doing this in a programmatic way using Python. This way you write as little HTML as possible, and all your logic stays in the forms and views files.

Fundamentals

For the rest of this document we will use the following example form for showing how to use a helper. This form is in charge of gathering some user information:

class ExampleForm(forms.Form):
    like_website = forms.TypedChoiceField(
        label = "Do you like this website?",
        choices = ((1, "Yes"), (0, "No")),
        coerce = lambda x: bool(int(x)),
        widget = forms.RadioSelect,
        initial = '1',
        required = True,
    )

    favorite_food = forms.CharField(
        label = "What is your favorite food?",
        max_length = 80,
        required = True,
    )

    favorite_color = forms.CharField(
        label = "What is your favorite color?",
        max_length = 80,
        required = True,
    )

    favorite_number = forms.IntegerField(
        label = "Favorite number",
        required = False,
    )

    notes = forms.CharField(
        label = "Additional notes or feedback",
        required = False,
    )

Let’s see how helpers works step by step, with some examples explained. First you will need to import FormHelper:

from crispy_forms.helper import FormHelper

Your helper can be a class level variable or an instance level variable, if you don’t know what this means you might want to read the article “Be careful how you use static variables in forms”. As a rule of thumb, if you are not going to manipulate a FormHelper in your code, like in a view, you should be using a static helper, otherwise you should be using an instance level helper. If you still don’t understand the subtle differences between both, use an instance level helper, because you won’t end up suffering side effects. As in the next steps I will show you how to manipulate the form helper, so we will create an instance level helper. This is how you would do it:

from crispy_forms.helper import FormHelper

class ExampleForm(forms.Form):
    [...]
    def __init__(self, *args, **kwargs):
        super(ExampleForm, self).__init__(*args, **kwargs)
        self.helper = FormHelper()

As you can see you need to call the base class constructor using super and override the constructor. This helper doesn’t set any form attributes, so it’s useless. Let’s see how to set up some basic FormHelper attributes:

from crispy_forms.helper import FormHelper
from crispy_forms.layout import Submit

class ExampleForm(forms.Form):
    [...]
    def __init__(self, *args, **kwargs):
        super(ExampleForm, self).__init__(*args, **kwargs)
        self.helper = FormHelper()
        self.helper.form_id = 'id-exampleForm'
        self.helper.form_class = 'blueForms'
        self.helper.form_method = 'post'
        self.helper.form_action = 'submit_survey'

        self.helper.add_input(Submit('submit', 'Submit'))

Note that we are importing a class called Submit that is a layout object. We will see what layout objects are in detail later on, for now on let’s just say that this adds a submit button to our form, so people can send their survey.

We’ve also done some helper magic. FormHelper has a list of attributes that can be set, that affect mainly form attributes. Our form will have as DOM id id-exampleForm, it will have as DOM CSS class blueForms, it will use http POST to send information and its action will be set to reverse(submit_survey).

Let’s see how to render the form in a template. Supposing we have the form in the template context as example_form, we would render it doing:

{% load crispy_forms_tags %}
{% crispy example_form example_form.helper %}

Notice that the {% crispy %} tags expects two parameters: first the form variable and then the helper. In this case we use the FormHelper attached to the form, but you could also create a FormHelper instance and pass it as a context variable. Most of the time, you will want to use the helper attached. Note that if you name your FormHelper attribute helper you will only need to do:

{% crispy form %}

This is exactly the html that you would get:

<form action="/submit/survey/" class="uniForm blueForms" method="post" id="id-exampleForm">
    <div style='display:none'>
        <input type='hidden' name='csrfmiddlewaretoken' value='a643fab735d5ce6377ff456e73c4b1af' />
    </div>
    <fieldset>
        <legend></legend>
        <div id="div_id_like_website" class="ctrlHolder">
            <label for="id_like_website" class="requiredField">¿Do you like this website?<span class="asteriskField">*</span></label>
            <ul>
                <li><label for="id_like_website_0"><input checked="checked" name="like_website" value="1" id="id_like_website_0" type="radio" class="radioselect" /> Yes</label></li>
                <li><label for="id_like_website_1"><input value="0" type="radio" class="radioselect" name="like_website" id="id_like_website_1" /> No</label></li>
            </ul>
        </div>
        <div id="div_id_favorite_food" class="ctrlHolder">
            <label for="id_favorite_food" class="requiredField">What is you favorite food?<span class="asteriskField">*</span></label>
            <input id="id_favorite_food" class="textinput textInput" type="text" name="favorite_food" maxlength="80" required="required" />
        </div>
        <div id="div_id_favorite_color" class="ctrlHolder">
            <label for="id_favorite_color" class="requiredField">What is you favorite color?<span class="asteriskField">*</span></label>
            <input id="id_favorite_color" class="textinput textInput" type="text" name="favorite_color" maxlength="80" required="required" />
        </div>
        <div id="div_id_favorite_number" class="ctrlHolder">
            <label for="id_favorite_number">Favorite number</label>
            <input id="id_favorite_number" type="text" name="favorite_number" class="textinput textInput" />
        </div>
        <div id="div_id_notes" class="ctrlHolder">
            <label for="id_notes">Additional notes or feedback</label>
            <input id="id_notes" type="text" name="notes" class="textinput textInput" />
        </div>
    </fieldset>
    <div class="buttonHolder">
        <input type="submit" name="submit" value="Submit" class="submit submitButton" id="submit-id-submit" />
    </div>
</form>

What you’ll get is the form rendered as HTML with awesome bits. Specifically...

  • Opening and closing form tags, with id, class, action and method set as in the helper:

    <form action="/submit/survey/" class="uniForm blueForms" method="post" id="id-exampleForm">
        [...]
    </form>
    
  • Django’s CSRF controls:

    <div style='display:none'>
        <input type='hidden' name='csrfmiddlewaretoken' value='a643fab735d5ce6377ff456e73c4b1af' />
    </div>
    
  • Submit button:

    <div class="buttonHolder">
        <input type="submit" name="submit" value="Submit" class="submit submitButton" id="submit-id-submit" />
    </div>
    

Manipulating a helper in a view

Let’s see how we could change any helper property in a view:

@login_required()
def inbox(request, template_name):
    example_form = ExampleForm()
    redirect_url = request.GET.get('next')

    # Form handling logic
    [...]

    if redirect_url is not None:
        example_form.helper.form_action = reverse('submit_survey') + '?next=' + redirectUrl

    return render_to_response(template_name, {'example_form': example_form}, context_instance=RequestContext(request))

We are changing form_action helper property in case the view was called with a next GET parameter.

Rendering several forms with helpers

Often we get asked: “How do you render two or more forms, with their respective helpers, using {% crispy %} tag, without having <form> tags rendered twice?” Easy, you need to set form_tag helper property to False in every helper:

self.helper.form_tag = False

Then you will have to write a little of html code surrounding the forms:

<form action="{% url 'submit_survey' %}" class="uniForm" method="post">
    {% crispy first_form %}
    {% crispy second_form %}
</form>

You can read a list of Helper attributes you can set and what they are for.

Change ‘*’ required fields

If you don’t like the use of * (asterisk) to denote required fields you have two options:

  • Asterisks have an asteriskField class set. So you can hide it using CSS rule:

    .asteriskField {
        display: none;
    }
    
  • Override field.html template with a custom one.

Make crispy-forms fail loud

By default when crispy-forms encounters errors, it fails silently, logs them and continues working if possible. A settings variable called CRISPY_FAIL_SILENTLY has been added so that you can control this behavior. If you want to raise exceptions instead of logging, telling you what’s going on when you are developing in debug mode, you can set it to:

CRISPY_FAIL_SILENTLY = not DEBUG

Change crispy-forms <input> default classes

Django fields generate default classes, crispy-forms handles these and adds other classes for compatibility with CSS frameworks.

For example a CharField generates an <input class="textinput" .... But in uni form we need the class to be textInput (with capital ‘I’), so crispy-forms leaves it like <input class="textinput textInput".... All official template packs are handled automatically, but maybe you are integrating a new CSS framework, or your company’s custom one, with crispy-forms and need to change the default conversions. For this you need to use a settings variable called CRISPY_CLASS_CONVERTERS, expected to be a Python dictionary:

CRISPY_CLASS_CONVERTERS = {'textinput': "textinput inputtext"}

For example this setting would generate <input class"textinput inputtext" .... The key of the dictionary textinput is the Django’s default class, the value is what you want it to be substituted with, in this case we are keeping textinput.

Render a form within Python code

Sometimes, it might be useful to render a form using crispy-forms within Python code, like a Django view, for that there is a nice helper render_crispy_form. The prototype of the method is render_crispy_form(form, helper=None, context=None). You can use it like this. Remember to pass your CSRF token to the helper method using the context dictionary if you want the rendered form to be able to submit.

AJAX validation recipe

One easy way to validate a crispy-form through AJAX and re-render the resulting form errors if any is to set up a view, that validates the form and renders its html using render_crispy_form to finally return this html to the client AJAX request. Let’s see an example.

Our server side code could be:

from crispy_forms.utils import render_crispy_form

@json_view
def save_example_form(request):
    form = ExampleForm(request.POST or None)
    if form.is_valid():
        # You could actually save through AJAX and return a success code here
        form.save()
        return {'success': True}

    # RequestContext ensures CSRF token is placed in newly rendered form_html
    request_context = RequestContext(request)
    form_html = render_crispy_form(form, context=request_context)
    return {'success': False, 'form_html': form_html}

I’m using a jsonview decorator from django-jsonview.

Note that in Django versions 1.8 and onwards, using RequestContext in this way will not work. Instead you can provide render_crispy_form with the necessary CSRF token with the following code

from django.core.context_processors import csrf ctx = {} ctx.update(csrf(request)) form_html = render_crispy_form(form, context=ctx)

In our client side using jQuery would look like:

var example_form = '#example-form';

$.ajax({
    url: "{% url 'save_example_form' %}",
    type: "POST",
    data: $(example_form).serialize(),
    success: function(data) {
        if (!(data['success'])) {
            // Here we replace the form, for the
            $(example_form).replaceWith(data['form_html']);
        }
        else {
            // Here you can show the user a success message or do whatever you need
            $(example_form).find('.success-message').show();
        }
    },
    error: function () {
        $(example_form).find('.error-message').show()
    }
});

Obviously, you can adjust this snippets to your needs, or class based views or favorite frontend library.

Warning

When replacing form html, you need to bind events using live or on jQuery method.

Bootstrap3 horizontal forms

_images/bootstrap3_horizontal_form.jpg

The way you do horizontal forms in Bootstrap version 3 is setting some col-lg-X classes in labels and divs wrapping fields. This would mean a lot of hassle updating your layout objects for settings these classes, too much verbosity. Instead some FormHelper attributes have been added to help you easily achieve this. You will need to set only three attributes:

helper.form_class = 'form-horizontal'
helper.label_class = 'col-lg-2'
helper.field_class = 'col-lg-8'
helper.layout = Layout(
    'email',
    'password',
    'remember_me',
    StrictButton('Sign in', css_class='btn-default'),
)

Of course you can set your widths as you like, it doesn’t have to be exactly like this.

Bootstrap3 inline forms

_images/bootstrap3_inline_form.jpg

The way you do inline forms in Bootstrap version 3 is:

helper.form_class = 'form-inline'
helper.field_template = 'bootstrap3/layout/inline_field.html'
helper.layout = Layout(
    'email',
    'password',
    'remember_me',
    StrictButton('Sign in', css_class='btn-default'),
)

If you need to set attributes in a field, you have to use InlineField instead of Field:

from crispy_forms.bootstrap import InlineField

helper.layout = Layout(
    InlineField('email', readonly=True),
    'password',
    [...]
)