After hours of reading semi related questions I finally figured this out.
You can't self reference a Model the way I was trying to do so there is no way to make django act the way I wanted using limit_choices_to because it can't find the id of a different ForeignKey in the same model.
This can apparently be done if you change the way django works, but a simpler way to solve this was to make changes to admin.py instead.
Here is what this looks like in my models.py now:
# models.py
class MovieCategory(models.Model):
category = models.ForeignKey(Category)
movie = models.ForeignKey(Movie)
prefix = models.ForeignKey('Prefix', blank=True, null=True)
number = models.DecimalField(verbose_name='Movie Number', max_digits=2,
blank=True, null=True, decimal_places=0)
I simply removed limit_choices_to entirely.
I found a similar problem here with the solution posted by Kyle Duncan.
The difference though is that this uses ManyToMany and not ForeignKey. That means I had to remove filter_horizontal = ('prefix',)
under my class MovieCategoryAdmin(admin.ModelAdmin):
as that is only for ManyToMany fields.
In admin.py I had to add from django import forms
at the top to create a form.
This is how the form looks:
class MovieCategoryForm(forms.ModelForm):
class Meta:
model = MovieCategory
fields = ['prefix']
def __init__(self, *args, **kwargs):
super(MovieCategoryForm, self).__init__(*args, **kwargs)
self.fields['prefix'].queryset = Prefix.objects.filter(
category_id=self.instance.category.id)
And my AdminModel:
class MovieCategoryAdmin(admin.ModelAdmin):
"""
Admin Class for 'Movie Category'.
"""
fieldsets = [
('Category', {'fields': ['category']}),
('Movie', {'fields': ['movie']}),
('Prefix', {'fields': ['prefix']}),
('Number', {'fields': ['number']}),
]
list_display = ('category', 'movie', 'prefix', 'number')
search_fields = ['category__category_name', 'movie__title', 'prefix__prefix']
form = MovieCategoryForm
This is exactly how Kyle describes it in his answer, except I had to add fields = ['prefix']
to the Form or it wouldn't run. If you follow his steps and remember to remove filter_horizontal and add the fields you're using it should work.
Edit: This solution works fine when editing, but not when creating a new entry because it can't search for the category id when one doesn't exits. I am trying to figure out how to solve this.