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72 | """
Subclass of ``template.Node`` for easy context updating.
"""
from django.db.models import get_model
from django.conf import settings
from django import template
class ContextUpdatingNode(template.Node):
"""
Node that updates the context with certain values.
Subclasses should define ``get_content()``, which should return a
dictionary to be added to the context.
"""
def render(self, context):
context.update(self.get_content(context))
return ''
def get_content(self, context):
raise NotImplementedError
class GenericContentNode(ContextUpdatingNode):
"""
Base Node class for retrieving objects from any model.
By itself, this class will retrieve a number of objects from a
particular model (specified by an "app_name.model_name" string)
and store them in a specified context variable (these are the
``num``, ``model`` and ``varname`` arguments to the constructor,
respectively), but is also intended to be subclassed for
customization.
There are two ways to add extra bits to the eventual database
lookup:
1. Add the setting ``GENERIC_CONTENT_LOOKUP_KWARGS`` to your
settings file; this should be a dictionary whose keys are
"app_name.model_name" strings corresponding to models, and whose
values are dictionaries of keyword arguments which will be
passed to ``filter()``.
2. Subclass and override ``_get_query_set``; all that's expected
is that it will return a ``QuerySet`` which will be used to
retrieve the object(s). The default ``QuerySet`` for the
specified model (filtered as described above) will be available
as ``self.query_set`` if you want to work with it.
"""
def __init__(self, model, num, varname):
self.num = num
self.varname = varname
lookup_dict = getattr(settings, 'GENERIC_CONTENT_LOOKUP_KWARGS', {})
self.model = get_model(*model.split('.'))
if self.model is None:
raise template.TemplateSyntaxError("Generic content tag got invalid model: %s" % model)
self.query_set = self.model._default_manager.filter(**lookup_dict.get(model, {}))
def _get_query_set(self):
return self.query_set
def get_content(self, context):
query_set = self._get_query_set()
if self.num == 1:
result = query_set[0]
else:
result = list(query_set[:self.num])
return { self.varname: result }
|
