Source Code for Module django.contrib.contenttypes.models

 1  from django.db import models 
 2  from django.utils.translation import ugettext_lazy as _ 
 3  from django.utils.encoding import smart_unicode 
 4   
 5 -class ContentTypeManager(models.Manager): 
 6   
 7      # Cache to avoid re-looking up ContentType objects all over the place. 
 8      # This cache is shared by all the get_for_* methods. 
 9      _cache = {} 
10       
11 -    def get_for_model(self, model): 
12          """ 
13          Returns the ContentType object for a given model, creating the 
14          ContentType if necessary. Lookups are cached so that subsequent lookups 
15          for the same model don't hit the database. 
16          """ 
17          opts = model._meta 
18          key = (opts.app_label, opts.object_name.lower()) 
19          try: 
20              ct = self.__class__._cache[key] 
21          except KeyError: 
22              # Load or create the ContentType entry. The smart_unicode() is  
23              # needed around opts.verbose_name_raw because name_raw might be a 
24              # django.utils.functional.__proxy__ object. 
25              ct, created = self.get_or_create( 
26                  app_label = opts.app_label, 
27                  model = opts.object_name.lower(),  
28                  defaults = {'name': smart_unicode(opts.verbose_name_raw)}, 
29              ) 
30              self._add_to_cache(ct) 
31               
32          return ct 
33           
34 -    def get_for_id(self, id): 
35          """ 
36          Lookup a ContentType by ID. Uses the same shared cache as get_for_model 
37          (though ContentTypes are obviously not created on-the-fly by get_by_id). 
38          """ 
39          try: 
40              ct = self.__class__._cache[id] 
41          except KeyError: 
42              # This could raise a DoesNotExist; that's correct behavior and will 
43              # make sure that only correct ctypes get stored in the cache dict. 
44              ct = self.get(pk=id) 
45              self._add_to_cache(ct) 
46          return ct 
47               
48 -    def clear_cache(self): 
49          """ 
50          Clear out the content-type cache. This needs to happen during database 
51          flushes to prevent caching of "stale" content type IDs (see 
52          django.contrib.contenttypes.management.update_contenttypes for where 
53          this gets called). 
54          """ 
55          self.__class__._cache.clear() 
56           
57 -    def _add_to_cache(self, ct): 
58          """Insert a ContentType into the cache.""" 
59          model = ct.model_class() 
60          key = (model._meta.app_label, model._meta.object_name.lower()) 
61          self.__class__._cache[key] = ct 
62          self.__class__._cache[ct.id] = ct 
63   
64 -class ContentType(models.Model): 
65      name = models.CharField(max_length=100) 
66      app_label = models.CharField(max_length=100) 
67      model = models.CharField(_('python model class name'), max_length=100) 
68      objects = ContentTypeManager() 
69       
70 -    class Meta: 
71          verbose_name = _('content type') 
72          verbose_name_plural = _('content types') 
73          db_table = 'django_content_type' 
74          ordering = ('name',) 
75          unique_together = (('app_label', 'model'),) 
76   
77 -    def __unicode__(self): 
78          return self.name 
79   
80 -    def model_class(self): 
81          "Returns the Python model class for this type of content." 
82          from django.db import models 
83          return models.get_model(self.app_label, self.model) 
84   
85 -    def get_object_for_this_type(self, **kwargs): 
86          """ 
87          Returns an object of this type for the keyword arguments given. 
88          Basically, this is a proxy around this object_type's get_object() model 
89          method. The ObjectNotExist exception, if thrown, will not be caught, 
90          so code that calls this method should catch it. 
91          """ 
92          return self.model_class()._default_manager.get(**kwargs) 
93