Django管理员未显示外键字段的选择

Question

I am creating a small chat app and I have problems making a message in the admin because of the drop down for the Messagemie model for field chat . Notice in the picture below it does not show the required values associated with the Conversation model. The values that the conversation field in the Conversation model accepts are of the form "number-number", eg 5-10 , 11-21 etc. Note that I have created a mechanism not shown below which converts such input formats to strings for non Django admin input (When users start a new conversation).

The conversation field is of type CharField . I suspect the reason why Django admin form does not show the required values is because of the field type, however I am not sure. Also it could be that because Django admin is not converting the input to string thus showing just Conversation object in the drop down. Why is Django admin not showing the correct values for the chat input field?

@python_2_unicode_compatible
class Conversation(models.Model):
    conversation = models.CharField(unique=True, max_length=150)
    email_1 = models.ForeignKey(Usermie, to_field="email", related_name="email_1_convo")
    email_2 = models.ForeignKey(Usermie, to_field="email", related_name="email_2_convo")



@python_2_unicode_compatible
class Messagemie(models.Model):
    sender = models.ForeignKey(Usermie, to_field="email", related_name="email_sender")
    receiver = models.ForeignKey(Usermie, to_field="email", related_name="email_receiver")
    # The username is the sender's username
    sender_username = models.CharField( max_length=50)
    receiver_username = models.CharField(max_length=50)
    message = models.TextField()
    chat = models.ForeignKey(Conversation, to_field="conversation", related_name="conversation_chat")

Picture showing Messagemie model chat field selection in admin

Picture of input values in Conversation model Django admin.

Answer 1

Django admin shows the string representation of the object in the dropdown. This could be obtained by calling str(object) . You can modify this behaviour by overriding the __str__ method in your class.

The implementation of the Django base model class ( django.db.models.Model ) has an implementation like below (for python3) -

def __str__(self):
    return str('%s object' % self.__class__.__name__)

which explains what you see. self.__class__.__name__ evaluates to "Conversation" , hence you end up seeing "Conversation object" in the dropdown.

To change this behaviour you can override the __str__ method to get the desired value returned. One sample implementation is below. You could modify the method easily to do include any logic you want.

class Conversation(models.Model):
    conversation = models.CharField(unique=True, max_length=150)
    email_1 = models.ForeignKey(Usermie, to_field="email", 
                               related_name="email_1_convo")
    email_2 = models.ForeignKey(Usermie, to_field="email", 
                                related_name="email_2_convo")

    def __str__(self):
        return self.conversation