Django CMS Attributes Field

An opinionated implementation of JSONField for arbitrary HTML element attributes.

Overview

This project aims to provide a sensible means of storing and managing arbitrary HTML element attributes for later emitting them into templates.

There are a wide variety of types of attributes and using the "normal" Django method of adding ModelFields for each on a business model is cumbersome at best and moreover may require related tables to allow cases where any number of the same type of attribute should be supported (i.e., data-attributes). This can contribute to performance problems.

To avoid these pitfalls, this package allows all of these attributes to be stored together in a single text field in the database as a JSON blob, but provides a nice widget to provide an intuitive, key/value pair interface and provide sensible validation of the keys used.

Example

The following is an example render of this field's widget render in the Django admin: (Note this example is from a django CMS project which uses djangocms-admin-style)

Installation

To install, simply use:

pip install djangocms-attributes-field

then, in your project's INSTALLED_APPS (if applicable) add:

# settings.py
...
INSTALLED_APPS = [
    ...,
    djangocms_attributes_field,
    ...,
]

Usage

AttributeField

To use this field in your Models.model:

# models.py
...
from django.db import models
from djangocms_attributes_field.fields import AttributesField
...
MyCoolModel(models.Model):
    ...
    attributes = AttributesField()

That's it!

There is an optional parameter that can be used when declaring the field:

``excluded_keys`` : This is a list of strings that will not be accepted as
                    valid keys

property: [field_name]_str

AttributeField will also provide a handy property [field_name]_str that will emit the stored key/value pairs as a string suitable for inclusion in your template for the target HTML element in question. You can use it like this:

# models.py
...
MyCoolModel(models.Model):
    ...
    html_attributes = AttributesField()


# templates/my_cool_project/template.html
...
<a href="..." {{ object.html_attributes_str }}>click me</a>
...

(Assuming that object is a context variable containing a MyCoolModel instance.)

In addition to nicely encapsulating the boring task of converting key/value pairs into a string with proper escaping and marking-safe, this property also ensures that existing key/value pairs with keys that have since been added to the field's excluded_keys are also not included in the output string.

AttributeWidget

The AttributesWidget is already used by default by the AttributesField, but there may be cases where you'd like to override its usage.

The widget supports two additional parameters:

``key_attrs`` : A dict of HTML attributes to apply to the key input field
``val_attrs`` : A dict of HTML attributes to apply to the value input field

These can be useful, for example, if it is necessary to alter the appearance of the widget's rendered appearance. Again, for example, let's say we needed to make the key and value inputs have specific widths. We could do this like so in our ModelForm:

# forms.py

from django import forms
from djangocms_attributes_field.widgets import AttributesWidget

MyCoolForm(forms.ModelForm):
    class Meta:
        fields = ['attributes', ...]

    def __init__(self, *args, **kwargs):
        super(MyCoolForm, self).__init__(*args, **kwargs)
        self.fields['attributes'].widget = AttributesWidget(key_attrs={'style': 'width:250px'},
                                                            val_attrs={'style': 'width:500px'})

mthornhill/djangocms-attributes-field