WTForms populate_obj problem

wtforms_populate_obj.py

from wtforms.form import Form
from wtforms.fields import TextField, TextAreaField, FieldFist, FormField


class PluginForm(Form):
   
    tags = TextField('Some random tags',)
    files = TextField('Some random files',)


class Plugin(object):
   
    form = PluginForm
   
   
class Page(object):

    @classmethod
    def register_plugin(cls, plugin):
        if issubclass(plugin, Plugin) and plugin not in cls._plugins:
            cls._plugins.append(plugin)

         
class PageForm(Form):

    title = TextField('Title of the Page',)
    body = TextAreaField('Enter the text for this page')
   
    ...
   
    plugins = FieldList(FormField(PluginForm))
   
    def __init__(self, *args, **kwargs):
       
        super(PageForm, self).__init__(*args, **kwargs)

        for plugin in Page._plugins:
            plugin_form_cls = plugin.form
            self.plugins.append_entry(FormField(plugin_form_cls))
           
           
Page.register_plugin(Plugin)

class AttributeDict(dict): 
    __getattr__ = dict.__getitem__
    __setattr__ = dict.__setitem__

def create_post(request):
    post = AttributeDict()
    form = PageForm(request.POST, obj=post)
"""
form.data contains following values:
{
    'body': u'',
    'meta_description': u'',
    'meta_keywords': u'',
    'title': u'seas',
    'published': True,
    'meta_title': u'',
    'publication_end_date': datetime.datetime(2012, 11, 19, 11, 43, 44),
    'plugins': [
        {'files': u'xxx', 'tags': u'xxx'},
        {'files': u'yyy', 'tags': u'yyy'},
    ],
    'publication_date': datetime.datetime(2012, 10, 19, 11, 43, 44),
    'in_navigation': False
}
"""
    if request.POST and form.validate():
        form.populate_obj(post)
        return redirect('/home')
    return render_to_response('edit_post.html', form=form)

create_post throws exception
TypeError: populate_obj: cannot find a value to populate from the provided obj or input data/defaults

with following stacktrace:
Traceback (most recent call last):
File "/Users/xxx/.virtualenvs/wtformstest/lib/python2.7/site-packages/flask/app.py", line 1701, in call
return self.wsgi_app(environ, start_response)
File "/Users/xxx/.virtualenvs/wtformstest/lib/python2.7/site-packages/flask/app.py", line 1689, in wsgi_app
response = self.make_response(self.handle_exception(e))
File "/Users/xxx/.virtualenvs/wtformstest/lib/python2.7/site-packages/flask/app.py", line 1687, in wsgi_app
response = self.full_dispatch_request()
File "/Users/xxx/.virtualenvs/wtformstest/lib/python2.7/site-packages/flask/app.py", line 1360, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/Users/xxx/.virtualenvs/wtformstest/lib/python2.7/site-packages/flask/app.py", line 1358, in full_dispatch_request
rv = self.dispatch_request()
File "/Users/xxx/.virtualenvs/wtformstest/lib/python2.7/site-packages/flask/app.py", line 1344, in dispatch_request
return self.view_functionsrule.endpoint
File "/Users/xxx/.virtualenvs/wtformstest/lib/python2.7/site-packages/flask/views.py", line 83, in view
return self.dispatch_request(_args, *_kwargs)
File "/Users/xxx/.virtualenvs/wtformstest/lib/python2.7/site-packages/flask/views.py", line 150, in dispatch_request
return meth(_args, *_kwargs)
File "/Users/xxx/Documents/Projekte/aaa/helpers.py", line 110, in decorated_function
ctx = f(_args, *_kwargs)
File "/Users/xxx/Documents/Projekte/aaa/blueprints/page/admin/views.py", line 30, in post
return super(CreateView, self).post(language)
File "/Users/xxx/Documents/Projekte/aaa/blueprints/admin/core/views.py", line 68, in post
self.form.populate_obj(entity)
File "/Users/xxx/Documents/Projekte/aaa/blueprints/page/admin/forms.py", line 59, in populate_obj
field.populate_obj(dummy, name)
File "/Users/xxx/.virtualenvs/wtformstest/lib/python2.7/site-packages/wtforms/fields/core.py", line 823, in populate_obj
field.populate_obj(fake_obj, 'data')
File "/Users/xxx/.virtualenvs/wtformstest/lib/python2.7/site-packages/wtforms/fields/core.py", line 699, in populate_obj
raise TypeError('populate_obj: cannot find a value to populate from the provided obj or input data/defaults')
TypeError: populate_obj: cannot find a value to populate from the provided obj or input data/defaults

Solved in:
https://groups.google.com/forum/#!msg/wtforms/5KQvYdLFiKE/TSgHIxmsI8wJ

Thanks! Your example saved me! I've used it to create a self contained example: https://github.com/sebkouba/dynamic-flask-form

Thank you for this gist.Check this I created this inspired from your gist.