OpenStack Study: fields.py

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# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2012 Nebula, Inc.

#

# Licensed under the Apache License, Version 2.0 (the "License"); you may

# not use this file except in compliance with the License. You may obtain

# a copy of the License at

#

# http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT

# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the

# License for the specific language governing permissions and limitations

# under the License.

from django.core import urlresolvers

from django.forms import fields

from django.forms import widgets

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class DynamicSelectWidget(widgets.Select):

"""A subclass of the ``Select`` widget which renders extra attributes for

use in callbacks to handle dynamic changes to the available choices.

"""

_data_add_url_attr = "data-add-item-url"

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    def render(self, *args, **kwargs):

        add_item_url = self.get_add_item_url()

        if add_item_url is not None:

            self.attrs.update({self._data_add_url_attr: add_item_url})

        return super(DynamicSelectWidget, self).render(*args, **kwargs)

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    def get_add_item_url(self):

        if callable(self.add_item_link):

            return self.add_item_link()

        try:

            if self.add_item_link_args:

                return urlresolvers.reverse(self.add_item_link,

                                            args=[self.add_item_link_args])

            else:

                return urlresolvers.reverse(self.add_item_link)

        except urlresolvers.NoReverseMatch:

            return self.add_item_link

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class DynamicChoiceField(fields.ChoiceField):

"""A subclass of ``ChoiceField`` with additional properties that make

dynamically updating its elements easier.

Notably, the field declaration takes an extra argument, ``add_item_link``

which may be a string or callable

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    def __init__(self,

                 add_item_link=None,

                 add_item_link_args=None,

                 *args,

                 **kwargs):

        super(DynamicChoiceField, self).__init__(*args, **kwargs)

        self.widget.add_item_link = add_item_link

        self.widget.add_item_link_args = add_item_link_args

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class DynamicTypedChoiceField(DynamicChoiceField, fields.TypedChoiceField):

"""Simple mix of ``DynamicChoiceField`` and ``TypedChoiceField``."""

pass