filter by ForeignKey in django admin

I have the following situation. There is a model for project and one for project image.

class Project(models.Model):
   name = models.CharField(max_length=300)
   ... #some more fields

class ProjectImage(models.Model):
   image = models.ImageField(upload_to = "uploads/")
   projekt = models.ForeignKey(Projekt)

Now, I'd like to be an admin panel user to filter out all projects in the admin area that don't have any image.

I already managed to have an icon in the overview that is green or red, wether it has an image attached or not. It works with a custom function on the model admin (This may not be the fastest solution but works ok).

class ProjectAdmin(admin.ModelAdmin):
    def image(self, obj):
        img = "no"
        images = ProjectImage.objects.only('id',).filter(project=obj)
        if images:
            img = "yes"
        return "<img src='"+ADMIN_MEDIA_PREFIX+"img/admin/icon-"+img+".gif' />"

    list_display = ('name', 'bild')

But AFAIK I can't use a similar method to just return a boolean and pass it as a custom filter.

I've also seen this: But it looks like a custom filter has to be attached to a model field and I don't have an image field in projects.

I there any other way to do this? thx


You should be able to do that with custom list filters, as of Django 1.4. You want something like this (untested):

from django.contrib.admin import SimpleListFilter

class HasImageFiter(SimpleListFilter):
    title = 'has image'
    parameter_name = 'has_image'

    def lookups(self, request, model_admin):
        return (
            ('Yes', 'Yes'),
            ('No', 'No'),

    def queryset(self, request, queryset):
        if self.value() == 'Yes':
            return queryset.filter(...)
        if self.value() == 'No':
            return queryset.filter(...)

class ProjectAdmin(admin.ModelAdmin):
    list_filter = (HasImageFilter,)

I'll leave you to write your queryset filtering (comment if you get stuck and I'll fill it in).

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