关于Django 框架的ContentType 模型

ContentType 模型对应数据库中django_content_type表，主要用户维护 django project 中所安装的所有用户模型

代码如下：

class ContentType(models.Model):
　　 #这三个字段分别表示 模型的用户化名称，模型所属app名称，模型名称
    name = models.CharField(max_length=100,verbose_name=_('name'))
    app_label = models.CharField(max_length=100)
    model = models.CharField(_('python model class name'), max_length=100)
    objects = ContentTypeManager()　　#自定义Mananger类

    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.using(self._state.db).get(**kwargs)

    def natural_key(self):
        return (self.app_label, self.model)