Inline Admin aware of Parent Object and affecting Generic Foreign Key Content Type choices

gistfile1.txt

# in models.py
from django.contrib.contenttypes.fields import GenericForeignKey
from django.contrib.contenttypes.models import ContentType
from django.db import models

class Screen(models.Model):
    # Screen Model: Ties into all shows, drives instance selection when using generic foreign keys
    name = models.CharField(max_length=50)
    limit = (models.Q(
        models.Q(app_label='case_story', model='casestoryshow') |
        models.Q(app_label='commerce', model='commerceshow') |
        models.Q(app_label='video', model='videoshow') |
        models.Q(app_label='weather', model='weathershow') |
        models.Q(app_label='factoid', model='factoidshow') |
        models.Q(app_label='patent', model='patentshow') |
        models.Q(app_label='tip', model='tipshow') |
        models.Q(app_label='security', model='securityshow')))

    ct_allowed = models.ManyToManyField(
        ContentType,
        related_name="screen_show_types",
        verbose_name="Allowed Modules",
        limit_choices_to=limit)

class Playlist(models.Model):
    name = models.CharField(max_length=105, help_text="Name")
    screen = models.ForeignKey(Screen, related_name="playlists")

class Slot(models.Model):
    playlist = models.ForeignKey(
        Playlist,
        related_name="slots")
    show_type = models.ForeignKey(
        ContentType,
        related_name="schedule_slot_show_types")
    show_id = models.PositiveIntegerField(verbose_name="Show name")
    show = GenericForeignKey("show_type", "show_id")
    position = models.PositiveSmallIntegerField("Position")


# in admin.py

from . import models, forms

class SlotInline(GrappelliSortableHiddenMixin, admin.TabularInline):
    model = models.Slot
    form = forms.SlotAdminForm
    formset = forms.SlotFormSet
    extra = 1
    autocomplete_lookup_fields = {"generic": [['show_type', 'show_id']]}
    sortable_field_name = "position"


@admin.register(models.Playlist)
class PlaylistAdmin(admin.ModelAdmin):
    list_display = ['name', 'screen', 'notes']
    list_filter = ['screen']
    change_list_template = "admin/change_list_filter_sidebar.html"
    inlines = [SlotInline]
    fields = ['name', 'screen', 'notes']

    def get_readonly_fields(self, request, obj=None):
        if obj is None:
            return []
        else:
            return ('screen',)

    def get_formsets_with_inlines(self, request, obj=None):
        # If parent object has not been saved yet / If there's no screen
        # hide inlines

        if obj is None:
            return []
        return super(PlaylistAdmin, self).get_formsets_with_inlines(request, obj)

    def get_fieldsets(self, request, obj=None):
        # If parent object has not been saved yet / If there's no screen
        #   hide all other fields (including inlines) and display instructions.
        # Instructions will not reappear after parent object has been saved.

        fieldsets = super(PlaylistAdmin, self).get_fieldsets(request, obj)
        if obj is None:
            fieldsets = ((None, {
                'fields': ('name', 'screen'),
                'description': '''Enter a show name, select a screen, and click
                    <strong>Save and continue editing</strong>.'''}),
            )
        return fieldsets

    def get_form(self, request, obj=None, **kwargs):
        # This method made obsolete by the use of custom formset shown above
        # Limit foreign key choices in an inline form:
        #  save obj reference to request scope for access in Inline
        request.parent_object = obj
        return super(PlaylistAdmin, self).get_form(request, obj, **kwargs)


# in forms.py

from django import forms
from django.contrib.admin.widgets import AdminDateWidget
from django.contrib.contenttypes.models import ContentType
from . import models

class SlotFormSet(forms.BaseInlineFormSet):
    def get_form_kwargs(self, index):
        # pass the parent object into the inline formset so it can be accessed from the inline form
        kwargs = super().get_form_kwargs(index)
        kwargs['parent_object'] = self.instance
        return kwargs


class SlotAdminForm(forms.ModelForm):
    pass

    class Meta:
        model = models.Slot
        fields = '__all__'

    def __init__(self, *args, parent_object, **kwargs):
        self.parent_object = parent_object
        super(SlotAdminForm, self).__init__(*args, **kwargs)
        # read the screen of the parent playlist and restrict to only the content types available there
        # print(self.instance, self.parent_object)
        if self.parent_object:
            self.fields['show_type'].queryset = self.parent_object.screen.ct_allowed.all()

    def clean_show_id(self):
        show_id = self.cleaned_data.get('show_id')
        show_type = self.cleaned_data.get('show_type')

        # lookup show
        show = ContentType.objects.get(app_label=show_type.app_label,
                                       model=show_type.model).get_object_for_this_type(id=show_id)

        # throw error if selected show is not on same screen as parent playlist
        if show.screen != self.instance.playlist.screen:
            raise forms.ValidationError('''Show belongs to {} screen and cannot be selected
                for this playlist.'''.format(show.screen))

        return show_id