Grokzen · September 4, 2024 11:27 · Nov 2, 2022 · Dec 7, 2021 · Dec 7, 2021 · Aug 13, 2015
diff --git a/Symmetrical ManyToMany Filter Horizontal in Django Admin.py b/Symmetrical ManyToMany Filter Horizontal in Django Admin.py
@@ -5,6 +5,12 @@
 When adding a many-to-many (m2m) relationship in Django, you can use a nice filter-style multiple select widget to manage entries. However, Django only lets you edit the m2m relationship this way on the forward model. The only built-in method in Django to edit the reverse relationship in the admin is through an InlineModelAdmin.
 
 Below is an example of how to create a filtered multiple select for the reverse relationship, so that editing entries is as easy as in the forward direction.
+
+IMPORTANT: I have no idea for what exact versions of Django this will work for, is compatible with or was intended for.
+
+I am sure this have stopped working slightly for new:er versions of Django. I do not use this myself currently with any new code so i can't really tell for sure.
+
+!! Use code at your own risk !!
 """
 
 ### pizza/models.py ###

diff --git a/...yToMany Filter Horizontal in Django Admin → ...Many Filter Horizontal in Django Admin.py b/...yToMany Filter Horizontal in Django Admin → ...Many Filter Horizontal in Django Admin.py
diff --git a/foo.py → ...yToMany Filter Horizontal in Django Admin b/foo.py → ...yToMany Filter Horizontal in Django Admin
diff --git a/gistfile1.txt → foo.py b/gistfile1.txt → foo.py
diff --git a/gistfile1.txt b/gistfile1.txt
@@ -1,3 +1,6 @@
+# Based on post from: https://snipt.net/chrisdpratt/symmetrical-manytomany-filter-horizontal-in-django-admin/#L-26
+# Only reposting to avoid loosing it.
+
 """
 When adding a many-to-many (m2m) relationship in Django, you can use a nice filter-style multiple select widget to manage entries. However, Django only lets you edit the m2m relationship this way on the forward model. The only built-in method in Django to edit the reverse relationship in the admin is through an InlineModelAdmin.
 

diff --git a/gistfile1.txt b/gistfile1.txt
@@ -0,0 +1,65 @@
+"""
+When adding a many-to-many (m2m) relationship in Django, you can use a nice filter-style multiple select widget to manage entries. However, Django only lets you edit the m2m relationship this way on the forward model. The only built-in method in Django to edit the reverse relationship in the admin is through an InlineModelAdmin.
+
+Below is an example of how to create a filtered multiple select for the reverse relationship, so that editing entries is as easy as in the forward direction.
+"""
+
+### pizza/models.py ###
+
+from django.db import models
+
+class Pizza(models.Model):
+  name = models.CharField(max_length=50)
+  toppings = models.ManyToManyField(Topping, related_name='pizzas')
+
+class Topping(models.Model):
+  name = models.CharField(max_length=50)
+
+### pizza/admin.py ###
+
+from django import forms
+from django.contrib import admin
+from django.utils.translation import ugettext_lazy as _
+from django.contrib.admin.widgets import FilteredSelectMultiple
+
+from .models import Pizza, Topping
+
+class PizzaAdmin(admin.ModelAdmin):
+  filter_horizonal = ('toppings',)
+
+class ToppingAdminForm(forms.ModelForm):
+  pizzas = forms.ModelMultipleChoiceField(
+    queryset=Pizza.objects.all(), 
+    required=False,
+    widget=FilteredSelectMultiple(
+      verbose_name=_('Pizzas'),
+      is_stacked=False
+    )
+  )
+
+  class Meta:
+    model = Topping
+
+  def __init__(self, *args, **kwargs):
+    super(ToppingAdminForm, self).__init__(*args, **kwargs)
+
+    if self.instance and self.instance.pk:
+      self.fields['pizzas'].initial = self.instance.pizzas.all()
+
+  def save(self, commit=True):
+    topping = super(ToppingAdminForm, self).save(commit=False)
+
+    if commit:
+      topping.save()
+
+    if topping.pk:
+      topping.pizzas = self.cleaned_data['pizzas']
+      self.save_m2m()
+
+    return topping
+
+class ToppingAdmin(admin.ModelAdmin):
+  form = ToppingAdminForm
+
+admin.site.register(Pizza, PizzaAdmin)
+admin.site.register(Topping, ToppingAdmin)
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