def __init__(self, disable=None, enable=None, html_field_name=None,
on_change=False, *args, **kwargs):
self._html_field_name = html_field_name
self._markdown = Markdown(disable=disable, enable=enable)
self._on_change = on_change
super(MarkdownField, self).__init__(*args, **kwargs)
class MarkdownField(models.TextField):
"""Stores markdown, converted to HTML and stored in another field on save.
By default, the resulting HTML is stored in the field whose name is given
by appending "_html" to this field's name. This can be changed by passing
an ``html_field_name`` argument to the field's constructor.
The markdown is converted to HTML on every save unless the constructor's
``on_change`` argument is ``True``. This causes a database query to be
performed on save to determine if any changes have been made.
With ``politics.utils.feature_markdown`` used to perform the conversion,
certain markdown features (e.g. images) can be enabled or disabled using
the keyword arguments of the same name. To disable images, for example:
.. code-block:: python
description = MarkdownField(disable=["images"])
description_html = models.TextField()
:param disable: Markdown features that are to be disabled.
:type disable: *Iterable* or ``None``
:param enable: Markdown features that are to be enabled.
:type enable: *Iterable* or ``None``
:param html_field_name: The name of the field in which the HTML will be
stored. If ``None``, this field's name plus "_html".
:type html_field_name: ``None`` or ``str``
:param on_change: If ``True``, the conversion will only be performed
if changes are detected. Requires a database query.
:type on_change: ``bool``
"""
def __init__(self, disable=None, enable=None, html_field_name=None,
on_change=False, *args, **kwargs):
self._html_field_name = html_field_name
self._markdown = Markdown(disable=disable, enable=enable)
self._on_change = on_change
super(MarkdownField, self).__init__(*args, **kwargs)
def contribute_to_class(self, cls, name):
# Determine the HTML field's name.
if getattr(self, "_html_field_name", None) is None:
self._html_field_name = "{0}_html".format(name)
super(MarkdownField, self).contribute_to_class(cls, name)
def pre_save(self, model_instance, add):
value = getattr(model_instance, self.attname)
# We can't detect changes if the model instance is new.
if self._on_change and not add:
model = model_instance.__class__
old_model_instance = model.objects.get(pk=model_instance.pk)
# If the value hasn't changed, don't perform the conversion.
if value == getattr(old_model_instance, self.attname):
return value
# Convert the markdown to HTML, store it.
result = self._markdown.convert(value)
setattr(model_instance, self._html_field_name, result)
return value
