Adds a generic wagtail_parent_filter for django admin

server/book/admin.py

@@ -1,20 +1,7 @@
 from django.contrib import admin
 
 from book.models import Book, Topic, Module
-
-
-class TopicListFilter(admin.SimpleListFilter):
-    title = 'topic modules'
-    parameter_name = 'topic_modules'
-
-    def lookups(self, request, model_admin):
-        return list((topic.slug, topic.title) for topic in Topic.objects.all())
-
-    def queryset(self, request, queryset):
-        filter_value = self.value()
-        topic = Topic.objects.filter(slug=filter_value).first()
-        if topic:
-            return Module.get_topic_modules(topic)
+from core.wagtail_utils import wagtail_parent_filter
 
 
 @admin.register(Book)
@@ -25,9 +12,10 @@ class BookAdmin(admin.ModelAdmin):
 @admin.register(Topic)
 class TopicAdmin(admin.ModelAdmin):
     list_display = ('title', 'slug', 'teaser', 'description')
+    list_filter = (wagtail_parent_filter(Book, Topic),)
 
 
 @admin.register(Module)
 class ModuleAdmin(admin.ModelAdmin):
     list_display = ('title', 'slug', 'meta_title', 'teaser')
-    list_filter = (TopicListFilter, )
+    list_filter = (wagtail_parent_filter(Topic, Module),)

server/core/wagtail_utils.py

@@ -0,0 +1,18 @@
+from django.contrib import admin
+
+
+def wagtail_parent_filter(parent_cls, child_cls):
+    class ParentValueFilter(admin.SimpleListFilter):
+        title = 'parent'
+        parameter_name = 'parent'
+
+        def lookups(self, request, model_admin):
+            return list((parent.slug, parent.title) for parent in parent_cls.objects.all())
+
+        def queryset(self, request, queryset):
+            filter_value = self.value()
+            parent = parent_cls.objects.filter(slug=filter_value).first()
+            if parent:
+                return child_cls.objects.filter(id__in=parent.get_child_ids()).live()
+
+    return ParentValueFilter