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−#!/usr/bin/python2.5
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−#
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−# Copyright 2008 the Melange authors.
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−#
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−# Licensed under the Apache License, Version 2.0 (the "License");
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−# you may not use this file except in compliance with the License.
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−# You may obtain a copy of the License at
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−#
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−#   http://www.apache.org/licenses/LICENSE-2.0
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−#
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−# Unless required by applicable law or agreed to in writing, software
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−# distributed under the License is distributed on an "AS IS" BASIS,
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−# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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−# See the License for the specific language governing permissions and
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−# limitations under the License.
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−
+
−"""This module defines classes and functions for Dynamic Forms.
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−"""
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−
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−__authors__ = [
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−    '"Sverre Rabbelier" <sverre@rabbelier.nl>',
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−    ]
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−
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−
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−from google.appengine.ext.db import djangoforms
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−
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−from soc.logic import dicts
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−
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−
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−class DynaFormMetaclass(djangoforms.ModelFormMetaclass):
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−  """The DynaForm Meta class, adding support for dynamically defined fields.
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−
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−  The new DynaForm class that is created by class function is very
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−  similar to one created by the regular djangoforms.ModelFormMetaclass.
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−  The only difference is that is the form class has a Meta property,
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−  it's 'dynaconf' field will be used to define additional properties
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−  in the form class.
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−
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−  The 'dynaconf' field (if present), is expected to be iterable as a
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−  dictionary (with iteritems). The keys are used as the property names,
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−  and the values are used as the property value.
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−  """
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−
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−  def __new__(cls, class_name, bases, attrs):
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−    """See djangoforms.ModelFormMetaclass on how the __new__ method
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−    is used, for an explanation on how this class modifies the default
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−    behavior, see the DynaFormMetaclass's docstring.
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−    """
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−
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−    # Retrieve the Meta class, if present
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−    meta = attrs.get('Meta', None)
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−    conf = None
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−
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−    # Try to retrieve the dynaconf property
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−    if meta:
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−      conf = getattr(meta, 'dynaconf', None)
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−
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−    # When found, extend the form's attribute's with the specified ones
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−    if conf:
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−      for key, value in conf.iteritems():
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−        attrs[key] = value
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−
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−    # Leave the rest to djangoforms.ModelFormMetaclass.
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−    return super(DynaFormMetaclass, cls).__new__(cls, class_name, bases, attrs)
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−
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−
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−def newDynaForm(dynamodel=None, dynabase=None, dynainclude=None, 
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−                dynaexclude=None, dynafields=None):
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−  """Creates a new form DynaForm class.
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−
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−  The returned class extends dynabase, but with the following additions:
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−  * It has a Meta class with the 'model', 'include', and 'exclude'
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−  fields set as specified by newDynaForm's keyword arguments.
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−  * It's __metaclass__ is set to DynaFormMetaclass (which inherits from
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−  the default djangoforms.ModelFormMetaclass).
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−  * The Meta class has an additional dynaconf field which is set to
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−  the dyanfields keyword argument passed to newDynaForm.
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−
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−  See DynaFormMetaclass for an explanation on how the dynafields
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−  property is used to construct the DynaForm class.
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−  """
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−
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−  class DynaForm(dynabase):
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−    """The dynamically created Form class
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−    """
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−
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−    __metaclass__ = DynaFormMetaclass
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−
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−    class Meta:
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−      """Inner Meta class that defines some behavior for the form.
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−      """
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−
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−      model = dynamodel
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−      include = dynainclude
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−      exclude = dynaexclude
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−      dynaconf = dynafields
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−
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−  return DynaForm
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−
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−
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−def extendDynaForm(dynaform, dynainclude=None, dynaexclude=None, 
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−                   dynafields=None):
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−  """Extends an existing dynaform.
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−
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−  If any of dynainclude, dynaexclude or dynafields are not present,
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−  they are retrieved from dynaform (if present in it's Meta class).
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−
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−  While it is rather useles to extend from a dynaform that does not have
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−  a Meta class, it is allowed, the resulting DynaForm is the same as if
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−  newDynaForm was called with all extendDynForm's keyword arguments.
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−  """
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−
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−  # Try to retrieve the Meta class from the existing dynaform
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−  meta = getattr(dynaform, 'Meta', None)
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−
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−  # If we find one, we can use it to 'extend' from
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−  if meta:
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−    dynamodel = getattr(meta, 'model', None)
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−
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−    if not dynainclude:
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−      dynainclude = getattr(meta, 'include', None)
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−
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−    if not dynaexclude:
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−      dynaexclude = getattr(meta, 'exclude', None)
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−
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−    # The most intersting parameter, the 'extra fields' dictionary
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−    dynaconf = getattr(meta, 'dynaconf', {})
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−    if not dynafields:
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−      dynafields = dynaconf
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−    else:
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−      dicts.merge(dynafields, dynaconf)
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−
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−  # Create a new DynaForm, using the properties we extracted
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−  return newDynaForm(
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−      dynamodel=dynamodel,
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−      dynabase=dynaform,
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−      dynainclude=dynainclude,
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−      dynaexclude=dynaexclude,
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−      dynafields=dynafields)