/template_utils/templatetags/generic_content.py

  1"""
  2Template tags which can do retrieval of content from any model.
  3
  4"""
  5
  6
  7from django import template
  8from django.db.models import get_model
  9
 10from template_utils.nodes import ContextUpdatingNode, GenericContentNode
 11
 12
 13class RandomObjectsNode(GenericContentNode):
 14    """
 15    A subclass of ``GenericContentNode`` which overrides
 16    ``_get_query_set`` to apply random ordering.
 17    
 18    """
 19    def _get_query_set(self):
 20        return self.query_set.order_by('?')
 21
 22
 23class RetrieveObjectNode(ContextUpdatingNode):
 24    """
 25    ``Node`` subclass which retrieves a single object -- by
 26    primary-key lookup -- from a given model.
 27
 28    Because this is a primary-key lookup, it is assumed that no other
 29    filtering is needed; hence, the settings-based filtering performed
 30    by ``GenericContentNode`` is not used here.
 31    
 32    """
 33    def __init__(self, model, pk, varname):
 34        self.pk = template.Variable(pk)
 35        self.varname = varname
 36        self.model = get_model(*model.split('.'))
 37        if self.model is None:
 38            raise template.TemplateSyntaxError("Generic content tag got invalid model: %s" % model)
 39    
 40    def get_content(self, context):
 41        return { self.varname: self.model._default_manager.get(pk=self.pk.resolve(context))}
 42
 43
 44def do_latest_object(parser, token):
 45    """
 46    Retrieves the latest object from a given model, in that model's
 47    default ordering, and stores it in a context variable.
 48    
 49    Syntax::
 50    
 51        {% get_latest_object [app_name].[model_name] as [varname] %}
 52    
 53    Example::
 54    
 55        {% get_latest_object comments.freecomment as latest_comment %}
 56    
 57    """
 58    bits = token.contents.split()
 59    if len(bits) != 4:
 60        raise template.TemplateSyntaxError("'%s' tag takes three arguments" % bits[0])
 61    if bits [2] != 'as':
 62        raise template.TemplateSyntaxError("second argument to '%s' tag must be 'as'" % bits[0])
 63    return GenericContentNode(bits[1], 1, bits[3])
 64
 65
 66def do_latest_objects(parser, token):
 67    """
 68    Retrieves the latest ``num`` objects from a given model, in that
 69    model's default ordering, and stores them in a context variable.
 70    
 71    Syntax::
 72    
 73        {% get_latest_objects [app_name].[model_name] [num] as [varname] %}
 74    
 75    Example::
 76    
 77        {% get_latest_objects comments.freecomment 5 as latest_comments %}
 78    
 79    """
 80    bits = token.contents.split()
 81    if len(bits) != 5:
 82        raise template.TemplateSyntaxError("'%s' tag takes four arguments" % bits[0])
 83    if bits [3] != 'as':
 84        raise template.TemplateSyntaxError("third argument to '%s' tag must be 'as'" % bits[0])
 85    return GenericContentNode(bits[1], bits[2], bits[4])
 86
 87def do_random_object(parser, token):
 88    """
 89    Retrieves a random object from a given model, and stores it in a
 90    context variable.
 91    
 92    Syntax::
 93    
 94        {% get_random_object [app_name].[model_name] as [varname] %}
 95    
 96    Example::
 97    
 98        {% get_random_object comments.freecomment as random_comment %}
 99    
100    """
101    bits = token.contents.split()
102    if len(bits) != 4:
103        raise template.TemplateSyntaxError("'%s' tag takes three arguments" % bits[0])
104    if bits [2] != 'as':
105        raise template.TemplateSyntaxError("second argument to '%s' tag must be 'as'" % bits[0])
106    return RandomObjectsNode(bits[1], 1, bits[3])
107
108
109def do_random_objects(parser, token):
110    """
111    Retrieves ``num`` random objects from a given model, and stores
112    them in a context variable.
113    
114    Syntax::
115    
116        {% get_random_objects [app_name].[model_name] [num] as [varname] %}
117    
118    Example::
119    
120        {% get_random_objects comments.freecomment 5 as random_comments %}
121    
122    """
123    bits = token.contents.split()
124    if len(bits) != 5:
125        raise template.TemplateSyntaxError("'%s' tag takes four arguments" % bits[0])
126    if bits [3] != 'as':
127        raise template.TemplateSyntaxError("third argument to '%s' tag must be 'as'" % bits[0])
128    return RandomObjectsNode(bits[1], bits[2], bits[4])
129
130
131def do_retrieve_object(parser, token):
132    """
133    Retrieves a specific object from a given model by primary-key
134    lookup, and stores it in a context variable.
135    
136    Syntax::
137    
138        {% retrieve_object [app_name].[model_name] [pk] as [varname] %}
139    
140    Example::
141    
142        {% retrieve_object flatpages.flatpage 12 as my_flat_page %}
143    
144    """
145    bits = token.contents.split()
146    if len(bits) != 5:
147        raise template.TemplateSyntaxError("'%s' tag takes four arguments" % bits[0])
148    if bits[3] != 'as':
149        raise template.TemplateSyntaxError("third argument to '%s' tag must be 'as'" % bits[0])
150    return RetrieveObjectNode(bits[1], bits[2], bits[4])
151
152register = template.Library()
153register.tag('get_latest_object', do_latest_object)
154register.tag('get_latest_objects', do_latest_objects)
155register.tag('get_random_object', do_random_object)
156register.tag('get_random_objects', do_random_objects)
157register.tag('retrieve_object', do_retrieve_object)