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Select multiple choices in a single Django model field

Project Description

Select multiple choices in a single Django model field. Use whenever you want to store multiple choices in a field without using a many-to-many relation.

Rendered using the multiselect.js plugin for jQuery [1]

[1]jquery.multi-select.js https://github.com/lou/multi-select

Quick Start

Important

Field attribute max_length must be set to a value longer than your longest expected encoded string

Important

Choices must be strings, not integers.

In your models add the select field choices normally:

# models.py

class Pizza(models.Model):
    ANCHOVIES = 'a'
    BLACK_OLIVES = 'b'
    PEPPERONI = 'p'
    MOZZARELLA = 'm'
    TOPPING_CHOICES = (
        (ANCHOVIES, 'Anchovies'),
        (BLACK_OLIVES, 'Black olives'),
        (PEPPERONI, 'Pepperoni'),
        (MOZZARELLA, 'Mozzarella'),
    )

    toppings = SelectMultipleField(
        max_length=10,
        choices=TOPPING_CHOICES
    )

Use a generic view or a modelform as usual. In your template you can use a regular form tag:

# template_form.html

<form action="" method="post">
  {{ form.as_p  }}
  <input type="submit" value="Submit">
</form>

This renders the following HTML:

# create.html

<form action="" method="post">
    <p>
      <label for="id_toppings">Toppings:</label>
      <select multiple="multiple" id="id_toppings" name="toppings"
          class="select-multiple-field">
        <option value="a">Anchovies</option>
        <option value="b">Black olives</option>
        <option value="p">Pepperoni</option>
        <option value="m">Mozzarella</option>
      </select>
    </p>
    <input type="submit" value="Submit">
</form>

Displaying stored choices

To display your choices, you will need to decode the field contents. This can be accomplished with a template tag:

# templatetags/pizza_tags.py

def decode_pie(ingredients):
    """
    Decode pizza pie toppings
    """
    decoder = dict(Pizza.TOPPING_CHOICES)
    decoded = [decoder[t] for t in ingredients]
    decoded.sort()
    return ', '.join(decoded)

register.filter('decode_pie', decode_pie)

In your template you need to import your tags and use them:

# details.html

{% load pizza_tags %}

{{ pizza.toppings|decode_pie }}

Encoding the choices

The choices that are selected are stored as comma-delimited text. Consider a pizza with the following toppings.

  • Pepperoni
  • Mozzarella

This would be stored as a character field as:

p,m

This encoded string is decoded to a Python list using functions in the codecs module:

>>> from select_multiple_field.codecs import *
>>> encoded = 'a,b,c'
>>> decoded = decode_csv_to_list(encoded)
>>> print decoded
[u'a', u'b', u'c']
>>> print type(decoded)
<type 'list'>

The method of encoding may limit your ability to search for choices.

Sample application

There is a sample application included if you downloaded the tarball. You can try it like this:

$ pwd
/home/user/teststuff/django-select-multiple-field
$ cd test_projects/django14
$ python manage.py syncdb
$ python manage.py runserver

Validating models...

0 errors found
Django version 1.4.19, using settings 'django14.settings'
Development server is running at http://127.0.0.1:8000/
Quit the server with CONTROL-C.

Troubleshooting

Django-select-multiple-field contains two test suites. One is for the field and one is for an implementation of the field in a Django 1.4.19 project.

You can run the field tests by downloading the tarball and running ‘test’ in setup.py:

$ python setup.py test

You can run the Django 1.4.19 demo test in a similar manner:

$ python setup.py test_demo

Needless to say you will need to have Django 1.4.19 or later installed.

Bugs! Help!!

If you find any bugs in this software please report them via the Github issue tracker [2] or send an email to code@kelvinwong.ca. Any serious security bugs should be reported via email only.

[2]Django-select-multiple-field issue tracker https://github.com/kelvinwong-ca/django-select-multiple-field/issues

Thank-you

Thank-you for taking the time to evaluate this software. I appreciate receiving feedback on your experiences using it and I welcome code contributions and development ideas.

http://www.kelvinwong.ca/coders

Release History

Release History

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0.0.1

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File Name & Checksum SHA256 Checksum Help Version File Type Upload Date
django-select-multiple-field-0.4.2.tar.gz (49.6 kB) Copy SHA256 Checksum SHA256 Source Dec 14, 2015

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