Question

My model definition:

class Thing1(models.Model):
    thing2s = models.ManyToManyField(Thing2, blank=True)

I have an instance of Thing2, called myThing2.
I want to do something like this:

Thing1.objects.get(thing2s__contains = myThing2)

That doesn’t work as functional code, but hopefully you get my point. (I’m trying to find a Thing1 that has myThing2 in it’s thing2s field.) How might I do that?

Thanks for the help!

Answer 1

Personally, I would add a ‘related_name’ to your many to many definition.

Something like

class Thing1(models.Model):
    thing2s = models.ManyToManyField(Thing2, blank=True, related_name='thing1s')

Then, from your Thing2, you can access the ‘thing1s’ that it relates to by….

thing2.thing1s.all()

But,I have to ask, as was stated above, if thing2 can only be related to a single thing1, then you should be using a ForeignKey(in Thing2, instead of Thing1) instead of ManyToMany. But, the above solution still works.

So, your classes would be….

class Thing1(models.Model):
    pass

class Thing2(models.Model):
    thing1 = models.ForeignKey(Thing1, blank=True, related_name='thing2s')

So, from a thing2, you could get at its single thing1 by simply….

a_thing1 = thing2.thing1

and from a thing1, you could get a list of all the thing2s that reference it via….

thing2s = thing1.thing2s.all()