Dynamically adding a form to a Django formset with Ajax

Question

I'd like to be able to automatically add new forms to a Django formset with an ajax function. I.e., the user clicks an "add" button and some javascript will add a new form (which is part of the formset) to the page.

Thanks for the help in advance. :-)

Answer 1

One option would be to create a formset with every possible form, but initially set the unrequired forms to hidden - ie, display: none;. When it's necessary to display a form, set it's css display to block or whatever is appropriate.

Without know more details of what your "Ajax" is doing, it's hard to give a more detailed response.

Answer 2

Simulate and imitate:

• Create a formset which corresponds to the situation before clicking the "add" button.
• Load the page, view the source and take a note of all <input> fields.
• Modify the formset to correspond to the situation after clicking the "add" button (change the number of extra fields).
• Load the page, view the source and take a note of how the <input> fields changed.
• Create some JavaScript which modifies the DOM in a suitable way to move it from the before state to the after state.
• Attach that JavaScript to the "add" button.

While I do know formsets use special hidden <input> fields and know approximately what the script must do, I don't recall the details off the top of my head. What I described above is what I would do in your situation.

Answer 3

put http://dpaste.com/hold/17376/ to django/contrib/admin/media/js/admin/AddInline.js

download jquery (jquery.com, version 1.3.6) and put it to django/contrib/admin/media/js/jquery.js

and then just add

class Media:

           js = ('/media/js/jquery.js', '/media/js/admin/AddInline.js', )

to your ModelAdmin definition for your model.

All inlines in your form will get magic 'Add another' link at the bottom.

Answer 4

This is how I do it, using jQuery:

My template:

<h3>My Services</h3>
{{ serviceFormset.management_form }}
{% for form in serviceFormset.forms %}
    <div class='table'>
    <table class='no_error'>
        {{ form.as_table }}
    </table>
    </div>
{% endfor %}
<input type="button" value="Add More" id="add_more">
<script>
    $('#add_more').click(function() {
        cloneMore('div.table:last', 'service');
    });
</script>

In a javascript file:

function cloneMore(selector, type) {
    var newElement = $(selector).clone(true);
    var total = $('#id_' + type + '-TOTAL_FORMS').val();
    newElement.find(':input').each(function() {
        var name = $(this).attr('name').replace('-' + (total-1) + '-','-' + total + '-');
        var id = 'id_' + name;
        $(this).attr({'name': name, 'id': id}).val('').removeAttr('checked');
    });
    newElement.find('label').each(function() {
        var newFor = $(this).attr('for').replace('-' + (total-1) + '-','-' + total + '-');
        $(this).attr('for', newFor);
    });
    total++;
    $('#id_' + type + '-TOTAL_FORMS').val(total);
    $(selector).after(newElement);
}

What it does:

cloneMore accepts selector as the first argument, and the type of formset as the 2nd one. What the selector should do is pass it what it should duplicate. In this case, I pass it div.table:last so that jQuery looks for the last table with a class of table. The :last part of it is important because the selector is also used to determine what the new form will be inserted after. More than likely you'd want it at the end of the rest of the forms. The type argument is so that we can update the management_form field, notably TOTAL_FORMS, as well as the actual form fields. If you have a formset full of, say, Client models, the management fields will have IDs of id_clients-TOTAL_FORMS and id_clients-INITIAL_FORMS, while the form fields will be in a format of id_clients-N-fieldname with N being the form number, starting with 0. So with the type argument the cloneMore function looks at how many forms there currently are, and goes through every input and label inside the new form replacing all the field names/ids from something like id_clients-(N)-name to id_clients-(N+1)-name and so on. After it is finished, it updates the TOTAL_FORMS field to reflect the new form and adds it to the end of the set.

This function is particularly helpful to me because the way it is setup it allows me to use it throughout the app when I want to provide more forms in a formset, and doesn't make me need to have a hidden "template" form to duplicate as long as I pass it the formset name and the format in which the forms are laid out. Hope it helps.

Answer 5

I've posted a snippet from an app I worked on a while back. Similar to Paolo's, but also allows you delete forms.

Answer 6

Paolo's suggestion works beautifully with one caveat - the browser's back/forward buttons.

The dynamic elements created with Paolo's script will not be rendered if the user returns to the formset using the back/forward button. An issue that may be a deal breaker for some.

Example:

1) User adds two new forms to the formset using the "add-more" button

2) User populates the forms and submits the formset

3) User clicks the back button in the browser

4) Formset is now reduced to the original form, all dynamically added forms are not there

This is not a defect with Paolo's script at all; but a fact of life with dom manipulation and browser's cache.

I suppose one could store the values of the form in the session and have some ajax magic when the formset loads to create the elements again and reload the values from the session; but depending on how anal you want to be about the same user and multiple instances of the form this may become very complicated.

Anyone has a good suggestion for dealing with this?

Thanks!

Answer 7

@Paolo Bergantino

to clone all the handlers attached just modify the line

var newElement = $(selector).clone();

for

var newElement = $(selector).clone(true);

to prevent this problem.

Answer 8

There is a small issue with the cloneMore function. Since it's also cleaning the value of the django auto-generated hidden fields, it causes django to complain if you try to save a formset with more than one empty form.

Here is a fix:

function cloneMore(selector, type) {
    var newElement = $(selector).clone(true);
    var total = $('#id_' + type + '-TOTAL_FORMS').val();
    newElement.find(':input').each(function() {
        var name = $(this).attr('name').replace('-' + (total-1) + '-','-' + total + '-');
        var id = 'id_' + name;

        if ($(this).attr('type') != 'hidden') {
            $(this).val('');
        }
        $(this).attr({'name': name, 'id': id}).removeAttr('checked');
    });
    newElement.find('label').each(function() {
        var newFor = $(this).attr('for').replace('-' + (total-1) + '-','-' + total + '-');
        $(this).attr('for', newFor);
    });
    total++;
    $('#id_' + type + '-TOTAL_FORMS').val(total);
    $(selector).after(newElement);
}