python - Django 模型的默认实例

Question

我的问题是:无论如何要为类语言创建一个默认实例吗？像这样:

class Language(models.
     default_instance = Language(name="unknown")
     name = models.CharField(max_length=100)

所以类学生可以使用这个:

class Student(models.Model):
         name = models.CharField(max_length=50)
         language = models.ForeignKey(Language, default = Language.default_instance.pk )

谢谢!

Answer 1

您可以通过覆盖保存方法来设置它:

#your model
class Student(models.Model):
  name = models.CharField(max_length=50)
  language = models.ForeignKey(Language)

    # override save
    def save(self,**args,**kwargs):
      if self.language is None:
        default_language = Language.objects.get(pk=1) #set to default
        self.language = default_language
    super(Student,self).save(self,*args,**kwargs) # the 'real' save

参见 here关于覆盖保存方法。