Django - assign m2m relationship in admin

Question

In the app I'm building some users have the role "Coder" and are assigned to "Assignments".
What I can't seem to get working is the process of an Admin assigning Coders to Assignments.

Here is the Model-Code I have so far (probably totally wrong):

class Coder(models.Model):
"""Every user can be a coder. Coders are assigned to Assignments"""
user = models.OneToOneField(User)

class Admin:
    list_display = ('',)
    search_fields = ('',)

def __unicode__(self):
    return u"Coders"

class Assignment(models.Model):
"""(Assignment description)"""
title = models.CharField(blank=True, max_length=100)
start_year = models.IntegerField(blank=True, null=True)
end_year = models.IntegerField(blank=True, null=True)
country = models.IntegerField(blank=True, null=True)
coders = models.ManyToManyField(Coder)

class Admin:
    list_display = ('',)
    search_fields = ('',)

def __unicode__(self):
    return u"Assignment"

And this is the admin-code:

class AssignmentCoderInline(admin.StackedInline):
model = Assignment.coders.through
can_delete = False
verbose_name_plural = 'coder'

class AssignmentAdmin(admin.ModelAdmin):
fieldsets = [
    ('Assignment', {'fields': ['title', 'start_year', 'end_year']})
]
inlines = (AssignmentCoderInline,)

class CoderInline(admin.StackedInline):
model = Coder
can_delete = False
verbose_name_plural = 'coder'

Now, when i'm in the admin, I want to create an assignment and add coders to it. Yet all I see when trying to do so is this:

How can I add one coder/user to an assignment, so I can later show him in a view all the assignments he has? This is probably a really dumb question, but please answer anyways, I greatly appreciate any help :)

Answer 1

If I'm not mistaken, it looks like you want to call a coder to a view, and then show all the assignments for an a user.

First, I might start by assigning a related_name to the coder and assignment models relationships with each other, so you can easily reference them later.

class Assignment(models.Model):
    coders = models.ManyToManyField(Coder, related_name='assignments')

class Coder(models.Model):
    user = models.OneToOneField(User, related_name="coder")

I'd then reference the user in a template as such using the one to one relationship:

    {% for assignment in user.coder.assignments.all %}

Also, looks like the problem is how you've got yout models setup. After reviewing the django.db.models.base for the "models.Model" class and "ModelBase" class, it looks like there is no "Admin" subclass. You'll probably want to remove those to start with.

Next, the __unicode__ field shows the default visible value which represents the object on the screen. In this case, you've forced it to be "Coders". If you had 5 coders to an assignment, you'd see "Coders, Coders, Coders, Coders, Coders" instead of "admin, user1, bob22, harry8, stadm1in", etc. Let's override the unicode to show something more meaningful. Since the coders field only has the user field, let's reference that by self.user.username. We'll change Assignment()'s unicode to self.title as well.

ModelForm doesn't have an 'Admin' subclass either, so let's remove that.

MODELS:


class Coder(models.Model):
    """Every user can be a coder. Coders are assigned to Assignments"""
    user = models.OneToOneField(User, related_name='coder')

    def __unicode__(self):
        return self.user.username


class Assignment(models.Model):
    """(Assignment description)"""
    title = models.CharField(blank=True, max_length=100)
    start_year = models.IntegerField(blank=True, null=True)
    end_year = models.IntegerField(blank=True, null=True)
    country = models.IntegerField(blank=True, null=True)
    coders = models.ManyToManyField(Coder, related_name='assignments')

    def __unicode__(self):
        return self.title


ADMIN:

class AssignmentCoderInline(admin.StackedInline):
    model = Assignment.coders.through
    can_delete = False
 #   verbose_name_plural = 'coder'

class AssignmentAdmin(admin.ModelAdmin):
    fieldsets = [
        ('Assignment', {'fields': ['title', 'start_year', 'end_year']})
    ]
    inlines = (AssignmentCoderInline,)