Using a django model as a field for another model?

Question

I have been tasked with creating Django Models for a hypothetical apartment booking application.

My question is: can I use a model that I've defined, as a field in another model?

For example, I will have one model called "Listing" that represents an apartment being listed.

class Listing(models.Model):
    address = models.IntegerField()
    owner = models.CharField(max_length=256)
    duration =  models.DurationField()
    price= models.IntegerField()

I also want to have a "Booking" model that represents an apartment once someone has booked it. It will have the exact same info as a Listing, with the addition of the username of the person who booked it. So can I have my Booking model use Listing as a field? And then just have one extra field for the booker's username.

Any other tips/critiques are highly appreciated as I am a complete beginner at Django.

Can a listing be booked by more than one person? You don't need a new field, you need a relationship — Sebastian Wozny
– Sebastian Wozny, Commented Nov 1, 2017 at 23:08
No, only by one person. So in my Booking model I would have something like " listing = models.OneToOneField(Listing, on_delete, etc...)? — KP.
– KP., Commented Nov 1, 2017 at 23:16

scharette · Accepted Answer · 2017-11-01 23:19:05Z

I'm not 100% sure what you mean by use Listing as a field

But to me, you should be looking at the different built-in model relationships that exist in Django.

In your particular case, you will probably want to use a One-to-One relationship like so,

class Listing(models.Model):
    address = models.IntegerField()
    owner = models.CharField(max_length=256)
    duration =  models.DurationField()
    price= models.IntegerField()

class Booking(models.Model):
    listing= models.OneToOneField(
    Listing,
    on_delete=models.CASCADE,
    )
    username = models.Charfield()

Now if a user can book more than one apartment at a time, you'll be interested in a ForeignKey relationship like so,

class Listing(models.Model):
    address = models.IntegerField()
    owner = models.CharField(max_length=256)
    duration =  models.DurationField()
    price= models.IntegerField()

class Booking(models.Model):
    listing= models.ForeignKey(
    Listing,
    on_delete=models.CASCADE,
    )
    username = models.Charfield()

Note that in both examples I used Charfield for the username, feel free to use whatever Django field you need.

schrodingerscatcuriosity · Accepted Answer · 2017-11-01 23:15:48Z

3

The concept of a model as field is odd. What you can do is establish relationships between models, or to inherit one from the other. Given your situation, you can maybe inherit Booking from Listing:

The docs on this topic.

You'll have something like this:

class Listing(models.Model):
    address = models.IntegerField()
    owner = models.CharField(max_length=256)
    duration =  models.DurationField()
    price= models.IntegerField()

class Booking(Listing):
    #your new fields

answered Nov 1, 2017 at 23:15

schrodingerscatcuriosity

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1 Comment

KP. Over a year ago

Thank you so much! Inheritance is what I was looking for

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