CODEWITHSUNDEEP
pythondjangomodel-view-controllerdjango-models
Yurrili
Yurrili

Reputation: 338

Abstract class as foreign key

Im trying to create relationship between class Locomotion and Section. Every Section has to have a king of Locomotion chosen (Class Locomotion is extended by Plain/Bus/Train etc.). And i'm getting the error about "Field defines a relation with model 'Locomotion', which is either not installed, or is abstract.". There is any way to do it? From what i read till now, there is no good way to do it, or i am mistaken?

My class Section:

class Section(RoadElements):
    locomotion = models.ForeignKey(Locomotion, on_delete=models.CASCADE)
    def __init__(self, *args, **kwargs):
        super(Section, self).__init__(*args, **kwargs)

    def __str__(self):
        return self.name

which extends class RoadElements, abstract as well.

My definition of Locomotion:

class Locomotion(models.Model):
    transportation_firm_name = models.CharField(max_length=200)
    transportation_number = models.CharField(max_length=200)
    departure_date_time = models.DateTimeField()
    arrival_date_time = models.DateTimeField()
    reservation = models.BooleanField(default=False)

    class Meta:
        abstract = True

And class extending, for example :

class Plain(Locomotion):
    seat_number = models.CharField(max_length=200)
    class_section = models.CharField(max_length=200)

Upvotes: 2

Views: 592

Answers (1)

wim
wim

Reputation: 363566

You can not have a foreign key to an abstract base class, because there is no database table for that class. In your example: there will be a database table with rows for Plain instances, but no table for Locomotion.

The usual way to do this is using a Generic Foreign Key to point to one of the child classes.

Upvotes: 1

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