CODEWITHSUNDEEP
djangodjango-models
knuckfubuck
knuckfubuck

Reputation: 969

Django Model: many-to-many or many-to-one?

I'm just learning django and following a tutorial. I have a Link and a Bookmark. Unlike the tutorial I'm following, I would like a link to be associated with only one Bookmark, but a Bookmark can have multiple links. Is this the way to setup the model?

class Link(models.Model):
    url = models.URLField(unique=True)
    bookmark = models.ForeignKey(Bookmark)

class Bookmark(models.Model):
    title = models.CharField(maxlength=200)
    user = models.ForeignKey(User)
    links = models.ManyToManyField(Link)

Upvotes: 4

Views: 1826

Answers (4)

user1051387
user1051387

Reputation: 11

if i change the code as this eg: class Bookmark(models.Model): title = models.CharField(max_length=200)

class Link(models.Model):
    url = models.URLField(unique=True)
    bookmark = models.ForeignKey(Bookmark)

is right relationship for them,

Upvotes: 1

user136565
user136565

Reputation:

No. Remove links from the Bookmark model, and to access the Link objects for a specific Bookmark you will use bookmark.link_set.all() (where bookmark is a specific Bookmark object). Django populates the reverse relationship for you.

Or if you so choose, provide your own related name in the bookmark ForeignKey, such as "links" if you do not like "link_set".

Upvotes: 5

Alex Martelli
Alex Martelli

Reputation: 881635

No, remove the links = statement from Bookmark -- what's predefined for you in bookmark is a property link_set that's the query for the links whose bookmark is this one (you can rename that property, but there's really no need).

Upvotes: 1

Ayman Hourieh
Ayman Hourieh

Reputation: 137156

It's enough to define the relationship in one of the models. Django will automatically create an attribute in the other model.

If you want a link to be associated with only one bookmark, define a foreign key in Link that refers back to a Bookmark object:

class Bookmark(models.Model):
    title = models.CharField(max_length=200)
    user = models.ForeignKey(User)

class Link(models.Model):
    url = models.URLField(unique=True)
    bookmark = models.ForeignKey(Bookmark)

To access the links of a bookmark, use bookmark.link_set. This attribute is automatically created by Django.

Upvotes: 4

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