app/django/contrib/contenttypes/models.py
author Sverre Rabbelier <srabbelier@gmail.com>
Sun, 07 Dec 2008 17:02:10 +0000
changeset 705 0ab17e14df95
parent 54 03e267d67478
permissions -rw-r--r--
Move document sidebar entries extraction to document.View This way other modules can benefit from the same logic. Also make use of the sidebar.getSidebarMenu method so that getMenusForScope is no longer specific to full menu's. Patch by: Sverre Rabbelier

from django.db import models
from django.utils.translation import ugettext_lazy as _
from django.utils.encoding import smart_unicode

class ContentTypeManager(models.Manager):

    # Cache to avoid re-looking up ContentType objects all over the place.
    # This cache is shared by all the get_for_* methods.
    _cache = {}
    
    def get_for_model(self, model):
        """
        Returns the ContentType object for a given model, creating the
        ContentType if necessary. Lookups are cached so that subsequent lookups
        for the same model don't hit the database.
        """
        opts = model._meta
        key = (opts.app_label, opts.object_name.lower())
        try:
            ct = self.__class__._cache[key]
        except KeyError:
            # Load or create the ContentType entry. The smart_unicode() is 
            # needed around opts.verbose_name_raw because name_raw might be a
            # django.utils.functional.__proxy__ object.
            ct, created = self.get_or_create(
                app_label = opts.app_label,
                model = opts.object_name.lower(), 
                defaults = {'name': smart_unicode(opts.verbose_name_raw)},
            )
            self._add_to_cache(ct)
            
        return ct
        
    def get_for_id(self, id):
        """
        Lookup a ContentType by ID. Uses the same shared cache as get_for_model
        (though ContentTypes are obviously not created on-the-fly by get_by_id).
        """
        try:
            ct = self.__class__._cache[id]
        except KeyError:
            # This could raise a DoesNotExist; that's correct behavior and will
            # make sure that only correct ctypes get stored in the cache dict.
            ct = self.get(pk=id)
            self._add_to_cache(ct)
        return ct
            
    def clear_cache(self):
        """
        Clear out the content-type cache. This needs to happen during database
        flushes to prevent caching of "stale" content type IDs (see
        django.contrib.contenttypes.management.update_contenttypes for where
        this gets called).
        """
        self.__class__._cache.clear()
        
    def _add_to_cache(self, ct):
        """Insert a ContentType into the cache."""
        model = ct.model_class()
        key = (model._meta.app_label, model._meta.object_name.lower())
        self.__class__._cache[key] = ct
        self.__class__._cache[ct.id] = ct

class ContentType(models.Model):
    name = models.CharField(max_length=100)
    app_label = models.CharField(max_length=100)
    model = models.CharField(_('python model class name'), max_length=100)
    objects = ContentTypeManager()
    
    class Meta:
        verbose_name = _('content type')
        verbose_name_plural = _('content types')
        db_table = 'django_content_type'
        ordering = ('name',)
        unique_together = (('app_label', 'model'),)

    def __unicode__(self):
        return self.name

    def model_class(self):
        "Returns the Python model class for this type of content."
        from django.db import models
        return models.get_model(self.app_label, self.model)

    def get_object_for_this_type(self, **kwargs):
        """
        Returns an object of this type for the keyword arguments given.
        Basically, this is a proxy around this object_type's get_object() model
        method. The ObjectNotExist exception, if thrown, will not be caught,
        so code that calls this method should catch it.
        """
        return self.model_class()._default_manager.get(**kwargs)