+
−"""
+
−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
+
−from django.http import HttpResponse, Http404
+
−from django.db.models.manager import Manager
+
−from django.db.models.query import QuerySet
+
−
+
−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 = {'mimetype': kwargs.pop('mimetype', None)}
+
−    return HttpResponse(loader.render_to_string(*args, **kwargs), **httpresponse_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.
+
−    """
+
−    if isinstance(klass, QuerySet):
+
−        return klass
+
−    elif isinstance(klass, Manager):
+
−        manager = klass
+
−    else:
+
−        manager = klass._default_manager
+
−    return manager.all()
+
−
+
−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)
+
−
+
−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