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"""
Helper functions for creating Form classes from Django models
and database field objects.
"""
from django.utils.translation import ugettext
from django.utils.encoding import smart_unicode
from util import ValidationError
from forms import BaseForm, SortedDictFromList
from fields import Field, ChoiceField
from widgets import Select, SelectMultiple, MultipleHiddenInput
__all__ = (
'save_instance', 'form_for_model', 'form_for_instance', 'form_for_fields',
'ModelChoiceField', 'ModelMultipleChoiceField'
)
def save_instance(form, instance, fields=None, fail_message='saved', commit=True):
"""
Saves bound Form ``form``'s cleaned_data into model instance ``instance``.
If commit=True, then the changes to ``instance`` will be saved to the
database. Returns ``instance``.
"""
from django.db import models
opts = instance.__class__._meta
if form.errors:
raise ValueError("The %s could not be %s because the data didn't validate." % (opts.object_name, fail_message))
cleaned_data = form.cleaned_data
for f in opts.fields:
if not f.editable or isinstance(f, models.AutoField) or not f.name in cleaned_data:
continue
if fields and f.name not in fields:
continue
setattr(instance, f.name, cleaned_data[f.name])
if commit:
instance.save()
for f in opts.many_to_many:
if fields and f.name not in fields:
continue
if f.name in cleaned_data:
setattr(instance, f.attname, cleaned_data[f.name])
# GOTCHA: If many-to-many data is given and commit=False, the many-to-many
# data will be lost. This happens because a many-to-many options cannot be
# set on an object until after it's saved. Maybe we should raise an
# exception in that case.
return instance
def make_model_save(model, fields, fail_message):
"Returns the save() method for a Form."
def save(self, commit=True):
return save_instance(self, model(), fields, fail_message, commit)
return save
def make_instance_save(instance, fields, fail_message):
"Returns the save() method for a Form."
def save(self, commit=True):
return save_instance(self, instance, fields, fail_message, commit)
return save
def form_for_model(model, form=BaseForm, fields=None, formfield_callback=lambda f: f.formfield()):
"""
Returns a Form class for the given Django model class.
Provide ``form`` if you want to use a custom BaseForm subclass.
Provide ``formfield_callback`` if you want to define different logic for
determining the formfield for a given database field. It's a callable that
takes a database Field instance and returns a form Field instance.
"""
opts = model._meta
field_list = []
for f in opts.fields + opts.many_to_many:
if not f.editable:
continue
if fields and not f.name in fields:
continue
formfield = formfield_callback(f)
if formfield:
field_list.append((f.name, formfield))
base_fields = SortedDictFromList(field_list)
return type(opts.object_name + 'Form', (form,),
{'base_fields': base_fields, '_model': model, 'save': make_model_save(model, fields, 'created')})
def form_for_instance(instance, form=BaseForm, fields=None, formfield_callback=lambda f, **kwargs: f.formfield(**kwargs)):
"""
Returns a Form class for the given Django model instance.
Provide ``form`` if you want to use a custom BaseForm subclass.
Provide ``formfield_callback`` if you want to define different logic for
determining the formfield for a given database field. It's a callable that
takes a database Field instance, plus **kwargs, and returns a form Field
instance with the given kwargs (i.e. 'initial').
"""
model = instance.__class__
opts = model._meta
field_list = []
for f in opts.fields + opts.many_to_many:
if not f.editable:
continue
if fields and not f.name in fields:
continue
current_value = f.value_from_object(instance)
formfield = formfield_callback(f, initial=current_value)
if formfield:
field_list.append((f.name, formfield))
base_fields = SortedDictFromList(field_list)
return type(opts.object_name + 'InstanceForm', (form,),
{'base_fields': base_fields, '_model': model, 'save': make_instance_save(instance, fields, 'changed')})
def form_for_fields(field_list):
"Returns a Form class for the given list of Django database field instances."
fields = SortedDictFromList([(f.name, f.formfield()) for f in field_list if f.editable])
return type('FormForFields', (BaseForm,), {'base_fields': fields})
class QuerySetIterator(object):
def __init__(self, queryset, empty_label, cache_choices):
self.queryset, self.empty_label, self.cache_choices = queryset, empty_label, cache_choices
def __iter__(self):
if self.empty_label is not None:
yield (u"", self.empty_label)
for obj in self.queryset:
yield (obj._get_pk_val(), smart_unicode(obj))
# Clear the QuerySet cache if required.
if not self.cache_choices:
self.queryset._result_cache = None
class ModelChoiceField(ChoiceField):
"A ChoiceField whose choices are a model QuerySet."
# This class is a subclass of ChoiceField for purity, but it doesn't
# actually use any of ChoiceField's implementation.
def __init__(self, queryset, empty_label=u"---------", cache_choices=False,
required=True, widget=Select, label=None, initial=None, help_text=None):
self.queryset = queryset
self.empty_label = empty_label
self.cache_choices = cache_choices
# Call Field instead of ChoiceField __init__() because we don't need
# ChoiceField.__init__().
Field.__init__(self, required, widget, label, initial, help_text)
self.widget.choices = self.choices
def _get_choices(self):
# If self._choices is set, then somebody must have manually set
# the property self.choices. In this case, just return self._choices.
if hasattr(self, '_choices'):
return self._choices
# Otherwise, execute the QuerySet in self.queryset to determine the
# choices dynamically. Return a fresh QuerySetIterator that has not
# been consumed. Note that we're instantiating a new QuerySetIterator
# *each* time _get_choices() is called (and, thus, each time
# self.choices is accessed) so that we can ensure the QuerySet has not
# been consumed.
return QuerySetIterator(self.queryset, self.empty_label, self.cache_choices)
def _set_choices(self, value):
# This method is copied from ChoiceField._set_choices(). It's necessary
# because property() doesn't allow a subclass to overwrite only
# _get_choices without implementing _set_choices.
self._choices = self.widget.choices = list(value)
choices = property(_get_choices, _set_choices)
def clean(self, value):
Field.clean(self, value)
if value in ('', None):
return None
try:
value = self.queryset.model._default_manager.get(pk=value)
except self.queryset.model.DoesNotExist:
raise ValidationError(ugettext(u'Select a valid choice. That choice is not one of the available choices.'))
return value
class ModelMultipleChoiceField(ModelChoiceField):
"A MultipleChoiceField whose choices are a model QuerySet."
hidden_widget = MultipleHiddenInput
def __init__(self, queryset, cache_choices=False, required=True,
widget=SelectMultiple, label=None, initial=None, help_text=None):
super(ModelMultipleChoiceField, self).__init__(queryset, None, cache_choices,
required, widget, label, initial, help_text)
def clean(self, value):
if self.required and not value:
raise ValidationError(ugettext(u'This field is required.'))
elif not self.required and not value:
return []
if not isinstance(value, (list, tuple)):
raise ValidationError(ugettext(u'Enter a list of values.'))
final_values = []
for val in value:
try:
obj = self.queryset.model._default_manager.get(pk=val)
except self.queryset.model.DoesNotExist:
raise ValidationError(ugettext(u'Select a valid choice. %s is not one of the available choices.') % val)
else:
final_values.append(obj)
return final_values
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