newforms: Added Widget.value_from_datadict hook, which allows a Widget to define how to convert its post data dictionary to a value. Implemented it for CheckboxSelectMultiple and updated unit tests

git-svn-id: http://code.djangoproject.com/svn/django/trunk@4136 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/newforms/forms.py

@@ -118,7 +118,10 @@ class Form(object):
             self.__errors = errors
             return
         for name, field in self.fields.items():
-            value = self.data.get(name, None)
+            # value_from_datadict() gets the data from the dictionary.
+            # Each widget type knows how to retrieve its own data, because some
+            # widgets split data over several HTML fields.
+            value = field.widget.value_from_datadict(self.data, name)
             try:
                 value = field.clean(value)
                 self.clean_data[name] = value

django/newforms/widgets.py

@@ -36,6 +36,13 @@ class Widget(object):
             attrs.update(extra_attrs)
         return attrs
 
+    def value_from_datadict(self, data, name):
+        """
+        Given a dictionary of data and this widget's name, returns the value
+        of this widget. Returns None if it's not provided.
+        """
+        return data.get(name, None)
+
     def id_for_label(self, id_):
         """
         Returns the HTML ID attribute of this Widget for use by a <label>,
@@ -186,12 +193,16 @@ class CheckboxSelectMultiple(SelectMultiple):
         cb = CheckboxInput(final_attrs)
         for option_value, option_label in chain(self.choices, choices):
             option_value = smart_unicode(option_value)
-            field_name = unicode(name + option_value)
+            field_name = name + option_value
             rendered_cb = cb.render(field_name, (option_value in str_values))
             output.append(u'<li><label>%s %s</label></li>' % (rendered_cb, escape(smart_unicode(option_label))))
         output.append(u'</ul>')
         return u'\n'.join(output)
 
+    def value_from_datadict(self, data, name):
+        data_list = [k for k, v in self.choices if data.get(name + k)]
+        return data_list or None
+
     def id_for_label(self, id_):
         # See the comment for RadioSelect.id_for_label()
         if id_:

tests/regressiontests/forms/tests.py

@@ -1471,6 +1471,7 @@ For a form with a <select>, use ChoiceField:
 <option value="J">Java</option>
 </select>
 
+Add widget=RadioSelect to use that widget with a ChoiceField.
 >>> class FrameworkForm(Form):
 ...     name = CharField()
 ...     language = ChoiceField(choices=[('P', 'Python'), ('J', 'Java')], widget=RadioSelect)
@@ -1545,6 +1546,46 @@ MultipleChoiceField is a special case, as its data is required to be a list:
 <option value="P" selected="selected">Paul McCartney</option>
 </select>
 
+MultipleChoiceField can also be used with the CheckboxSelectMultiple widget.
+>>> class SongForm(Form):
+...     name = CharField()
+...     composers = MultipleChoiceField(choices=[('J', 'John Lennon'), ('P', 'Paul McCartney')], widget=CheckboxSelectMultiple)
+>>> f = SongForm()
+>>> print f['composers']
+<ul>
+<li><label><input type="checkbox" name="composersJ" /> John Lennon</label></li>
+<li><label><input type="checkbox" name="composersP" /> Paul McCartney</label></li>
+</ul>
+>>> f = SongForm({'composers': ['J']})
+>>> print f['composers']
+<ul>
+<li><label><input checked="checked" type="checkbox" name="composersJ" /> John Lennon</label></li>
+<li><label><input type="checkbox" name="composersP" /> Paul McCartney</label></li>
+</ul>
+>>> f = SongForm({'composers': ['J', 'P']})
+>>> print f['composers']
+<ul>
+<li><label><input checked="checked" type="checkbox" name="composersJ" /> John Lennon</label></li>
+<li><label><input checked="checked" type="checkbox" name="composersP" /> Paul McCartney</label></li>
+</ul>
+
+When using CheckboxSelectMultiple, the framework automatically converts the
+data in clean_data to a list of values, rather than the underlying HTML form
+field name.
+>>> f = SongForm({'name': 'Yesterday'})
+>>> f.errors
+{'composers': [u'This field is required.']}
+>>> f = SongForm({'name': 'Yesterday', 'composersJ': 'on'})
+>>> f.errors
+{}
+>>> f.clean_data
+{'composers': [u'J'], 'name': u'Yesterday'}
+>>> f = SongForm({'name': 'Yesterday', 'composersJ': 'on', 'composersP': 'on'})
+>>> f.errors
+{}
+>>> f.clean_data
+{'composers': [u'J', u'P'], 'name': u'Yesterday'}
+
 There are a couple of ways to do multiple-field validation. If you want the
 validation message to be associated with a particular field, implement the
 clean_XXX() method on the Form, where XXX is the field name. As in