title: How to access other model's attribute in one model via Foreign key in django?
body: <pre><code>class Grade(models.Model):
      name = models.CharField(u'年级', max_length=64)
      school = models.ForeignKey('School', verbose_name=u'学校')
  
      def __unicode__(self):
          return self.name
  
  class Class(models.Model):
      name = models.CharField(u'班级', max_length=64)
      grade = models.ForeignKey('Grade', verbose_name=u'年级', related_name='grade')
  
      def getGradeName(self):
          return self.grade.name
  
      def __unicode__(self):
          return self.name
  
  class Student(models.Model):
      name = models.CharField(u'姓名', max_length=64)
      sex = models.CharField(u'性别', max_length=64)
      id_num = models.CharField(u'身份证号', max_length=64)
      student_num = models.CharField(u'学号', max_length=64)
      class_id = models.ForeignKey('Class', verbose_name=u'班级', related_name='class_id')
      grade = class_id.name
  
      def __unicode__(self):
          return self.name
  </code></pre>
  
  <p>I want to get students'class'grade and then assign it to grade in Model Student.</p>
  
  <p>How to get Grade's name in model Student?</p>