Fix #3

README.md

@@ -21,12 +21,15 @@ Form must inherit from ChainedChoicesForm which loads the options when there is
         field_two = ChainedChoiceField(parent_field='field_one', ajax_url='/chainedselectchoices')
         field_three = ChainedChoiceField(parent_field='field_two', ajax_url='/chainedselectchoices')
 
+If the `parent_field` is a foreign key, then inherit from FKChainedChoicesForm
+instead. This obtains the `id` of the field, and ensures that the widget works
+correctly with both new and existing instances.
 
 Ajax call is made whenever the parent field is changed. You must set up the ajax to return json list of lists.
 
     class ChainedSelectChoices(BaseDetailView):
         """
-        View to handel the ajax request for the field options.
+        View to handle the ajax request for the field options.
         """
 
         def get(self, request, *args, **kwargs):
@@ -45,4 +48,3 @@ Ajax call is made whenever the parent field is changed. You must set up the ajax
             )
             add_never_cache_headers(response)
             return response
-

chained_selectbox/form_fields.py

@@ -16,8 +16,6 @@ def __init__(self, parent_field, ajax_url, choices=None, *args, **kwargs):
 
         super(ChainedChoiceField, self).__init__(choices=self.choices, *args, **defaults)
 
-
     def valid_value(self, value):
         "Dynamic choices so just return True for now"
         return True
-

chained_selectbox/forms.py

@@ -7,19 +7,43 @@
 
 class ChainedChoicesForm(forms.ModelForm):
     """
-    Form class to be used with ChainedChoiceField and ChainedSelect widget
-    If there is already an instance (i.e. editing) then the options will be loaded when the form is built.
+    Form class to be used with ChainedChoiceField and ChainedSelect widget If
+    there is already an instance (i.e. editing) then the options will be loaded
+    when the form is built.
     """
     def __init__(self, *args, **kwargs):
         super(ChainedChoicesForm, self).__init__(*args, **kwargs)
-        if kwargs.has_key('instance'):
+        if "instance" in kwargs:
             instance = kwargs['instance']
             c = Client()
 
             for field_name, field in self.fields.items():
                 if hasattr(field, 'parent_field'):
                     article = c.get(field.ajax_url, {
-                        'field_name' : field_name,
-                        'parent_value' : getattr(instance, field.parent_field)
+                        'field_name': field_name,
+                        'parent_value': getattr(instance, field.parent_field)
+                    })
+                    field.choices = json.loads(article.content)
+
+
+class FKChainedChoicesForm(forms.ModelForm):
+    """
+    Similar to ChainedChoicesForm - however, this uses parent_field_id rather than
+    parent_field.
+    """
+    def __init__(self, *args, **kwargs):
+        super(FKChainedChoicesForm, self).__init__(*args, **kwargs)
+        if "instance" in kwargs:
+            instance = kwargs['instance']
+            c = Client()
+
+            for field_name, field in self.fields.items():
+                if hasattr(field, 'parent_field'):
+                    article = c.get(field.ajax_url, {
+                        'field_name': field_name,
+                        'parent_value': getattr(
+                            instance,
+                            "%s_id" % field.parent_field
+                            )
                     })
                     field.choices = json.loads(article.content)

chained_selectbox/widgets.py

@@ -2,12 +2,15 @@
 from django.contrib.admin.templatetags.admin_static import static
 from django.utils.safestring import mark_safe
 
+
 class ChainedSelect(Select):
     """
-    A ChoiceField widget where the options for the select are dependant on the value of the parent select field.
-    When the parent field is changed an ajax call is made to determine the options.
+    A ChoiceField widget where the options for the select are dependant on the
+    value of the parent select field. When the parent field is changed an ajax
+    call is made to determine the options.
 
-    Form must inherit from ChainedChoicesForm which loads the options when there is already an instance.
+     Form must inherit from ChainedChoicesForm which loads the options when
+    there is already an instance.
 
     class StandardModelForm(ChainedChoicesForm):
         field_one = forms.ChoiceField(choices=(('', '------------'), (1, '1'), (2, '2'), (3, '3'), (4, '4'), (5, '5'), ))
@@ -21,16 +24,22 @@ def __init__(self, parent_field=None, ajax_url=None, *args, **kwargs):
         super(ChainedSelect, self).__init__(*args, **kwargs)
 
     class Media:
-        js = ['admin/js/jquery.min.js', 'admin/js/jquery.init.js', 'js/chained-select.min.js']
+        js = [
+            'admin/js/jquery.min.js',
+            'admin/js/jquery.init.js',
+            'js/chained-select.min.js'
+            ]
 
     def render(self, name, value, attrs={}, choices=()):
         field_prefix = attrs['id'][:attrs['id'].rfind('-') + 1]
+
+        # this variable is set but never used
         formset_prefix = attrs['id'][:attrs['id'].find('-') + 1]
 
         if not field_prefix:
-            paretnfield_id = "id_" + self.parent_field
+            parentfield_id = "id_" + self.parent_field
         else:
-            paretnfield_id = field_prefix + self.parent_field
+            parentfield_id = field_prefix + self.parent_field
 
         attrs['ajax_url'] = self.ajax_url
 
@@ -41,15 +50,15 @@ def render(self, name, value, attrs={}, choices=()):
         //<![CDATA[
         (function($) {
             $(document).ready(function(){
-                var parent_field = $("#%(paretnfield_id)s");
+                var parent_field = $("#%(parentfield_id)s");
                 parent_field.addClass('chained-parent-field');
                 parent_field.attr('chained_id', "%(chained_id)s");
             })
         })(django.jQuery);
         //]]>
         </script>
 
-        """ % {"paretnfield_id":paretnfield_id, 'chained_id': attrs['id']}
+        """ % {"parentfield_id": parentfield_id, 'chained_id': attrs['id']}
 
         output += js