"""
This module collects helper functions and classes that "span" multiple levels
of MVC. In other words, these functions/classes introduce controlled coupling
for convenience's sake.
"""
from django.template import loader, RequestContext
from django.http import HttpResponse, Http404
from django.http import HttpResponseRedirect, HttpResponsePermanentRedirect
from django.db.models.base import ModelBase
from django.db.models.manager import Manager
from django.db.models.query import QuerySet
from django.core import urlresolvers
from django.utils import six
from django.utils.encoding import force_text
from django.utils.functional import Promise
[docs]def render_to_response(*args, **kwargs):
"""
Returns a HttpResponse whose content is filled with the result of calling
django.template.loader.render_to_string() with the passed arguments.
"""
httpresponse_kwargs = {'content_type': kwargs.pop('content_type', None)}
return HttpResponse(loader.render_to_string(*args, **kwargs), **httpresponse_kwargs)
[docs]def render(request, *args, **kwargs):
"""
Returns a HttpResponse whose content is filled with the result of calling
django.template.loader.render_to_string() with the passed arguments.
Uses a RequestContext by default.
"""
httpresponse_kwargs = {
'content_type': kwargs.pop('content_type', None),
'status': kwargs.pop('status', None),
}
if 'context_instance' in kwargs:
context_instance = kwargs.pop('context_instance')
if kwargs.get('current_app', None):
raise ValueError('If you provide a context_instance you must '
'set its current_app before calling render()')
else:
current_app = kwargs.pop('current_app', None)
context_instance = RequestContext(request, current_app=current_app)
kwargs['context_instance'] = context_instance
return HttpResponse(loader.render_to_string(*args, **kwargs),
**httpresponse_kwargs)
[docs]def redirect(to, *args, **kwargs):
"""
Returns an HttpResponseRedirect to the appropriate URL for the arguments
passed.
The arguments could be:
* A model: the model's `get_absolute_url()` function will be called.
* A view name, possibly with arguments: `urlresolvers.reverse()` will
be used to reverse-resolve the name.
* A URL, which will be used as-is for the redirect location.
By default issues a temporary redirect; pass permanent=True to issue a
permanent redirect
"""
if kwargs.pop('permanent', False):
redirect_class = HttpResponsePermanentRedirect
else:
redirect_class = HttpResponseRedirect
return redirect_class(resolve_url(to, *args, **kwargs))
def _get_queryset(klass):
"""
Returns a QuerySet from a Model, Manager, or QuerySet. Created to make
get_object_or_404 and get_list_or_404 more DRY.
Raises a ValueError if klass is not a Model, Manager, or QuerySet.
"""
if isinstance(klass, QuerySet):
return klass
elif isinstance(klass, Manager):
manager = klass
elif isinstance(klass, ModelBase):
manager = klass._default_manager
else:
if isinstance(klass, type):
klass__name = klass.__name__
else:
klass__name = klass.__class__.__name__
raise ValueError("Object is of type '%s', but must be a Django Model, "
"Manager, or QuerySet" % klass__name)
return manager.all()
[docs]def get_object_or_404(klass, *args, **kwargs):
"""
Uses get() to return an object, or raises a Http404 exception if the object
does not exist.
klass may be a Model, Manager, or QuerySet object. All other passed
arguments and keyword arguments are used in the get() query.
Note: Like with get(), an MultipleObjectsReturned will be raised if more than one
object is found.
"""
queryset = _get_queryset(klass)
try:
return queryset.get(*args, **kwargs)
except queryset.model.DoesNotExist:
raise Http404('No %s matches the given query.' % queryset.model._meta.object_name)
[docs]def get_list_or_404(klass, *args, **kwargs):
"""
Uses filter() to return a list of objects, or raise a Http404 exception if
the list is empty.
klass may be a Model, Manager, or QuerySet object. All other passed
arguments and keyword arguments are used in the filter() query.
"""
queryset = _get_queryset(klass)
obj_list = list(queryset.filter(*args, **kwargs))
if not obj_list:
raise Http404('No %s matches the given query.' % queryset.model._meta.object_name)
return obj_list
def resolve_url(to, *args, **kwargs):
"""
Return a URL appropriate for the arguments passed.
The arguments could be:
* A model: the model's `get_absolute_url()` function will be called.
* A view name, possibly with arguments: `urlresolvers.reverse()` will
be used to reverse-resolve the name.
* A URL, which will be returned as-is.
"""
# If it's a model, use get_absolute_url()
if hasattr(to, 'get_absolute_url'):
return to.get_absolute_url()
if isinstance(to, Promise):
# Expand the lazy instance, as it can cause issues when it is passed
# further to some Python functions like urlparse.
to = force_text(to)
if isinstance(to, six.string_types):
# Handle relative URLs
if any(to.startswith(path) for path in ('./', '../')):
return to
# Next try a reverse URL resolution.
try:
return urlresolvers.reverse(to, args=args, kwargs=kwargs)
except urlresolvers.NoReverseMatch:
# If this is a callable, re-raise.
if callable(to):
raise
# If this doesn't "feel" like a URL, re-raise.
if '/' not in to and '.' not in to:
raise
# Finally, fall back and assume it's a URL
return to
Feb 24, 2017