yafowil.yaml 0.9.1

Create YAML file containing form description

factory: form
name: demo_form
props:
    action: context.form_action
widgets:
- title:
    factory: label:field:error:text
    value: expr:context.get('title', '')
    props:
        label: i18n:Title
        required: No title given
- description:
    factory: label:field:textarea
    value: expr:context.get('description', '')
    props:
        label: i18n:Description
        rows: 5
- save:
    factory: submit
    props:
        action: save
        expression: True
        handler: context.save
        next: context.next
        label: i18n:Save

Each widget node is represented by an associative array. Keys are mapping to corresponding arguments of yafowil.base.factory signature:

factory

Chained factory registration names.

name

Widget name. Only required on root, for children widget key is used.

value

Widget value or callable/expression returning widget value.

props

Widget properties as associative array.

custom

Custom widget properties as associative array.

widgets

Child widgets as list. Each child widget is an associative array with one key - the widget name - containing again an associative array with the keys descibed here.

Resolution of definition values

Beside static values, definitions may contain python expressions, i18n message strings, access to a rendering context and pointers to callables.

• If definition value starts with i18n:, a message string gets created by calling given message factory.

• If definition value starts with expr:, a callback wrapper is created which gets executed each time the widget tree gets rendered. For security reasons, only rendering context is accessible in expressions.

• If definition value starts with context, rendering context is used to lookup callbacks. If lookup fails, return definition value as string.

• If ‘.’ is found in definition value, try to lookup callback from module path. If lookup fails, return definition value as string.

Define rendering context

A rendering context is provided by a class. Refering to the form description example above, this looks like:

>>> class FormRenderingContext(object):
...
...     def get(self, key, default=None):
...         # do data lookup here
...         value = key
...         return value
...
...     def form_action(self, widget, data):
...         # create and return form action URL
...         return 'http://example.com/form_action'
...
...     def save(self, widget, data):
...         # extract and save form data
...         pass
...
...     def next(self, request):
...         # compute and return next URL
...         return 'http://example.com/form_action_succeed'

Create Message Factory

Usually someone uses message factories from pyramid.i18n or zope.i18nmessageid. See refering documentation for details.

>>> message_factory = lambda x: x

Obtaining YAML Forms

To obtain a yafowil widget tree from YAML, use yafowil.yaml.parse_from_YAML:

>>> import yafowil.loader
>>> from yafowil.yaml import parse_from_YAML

>>> rendering_context = FormRenderingContext()
>>> form = parse_from_YAML(demo_form_path,
...                        context=rendering_context,
...                        message_factory=message_factory)

This results to…:

>>> form.printtree()
<class 'yafowil.base.Widget'>: demo_form
  <class 'yafowil.base.Widget'>: title
  <class 'yafowil.base.Widget'>: description
  <class 'yafowil.base.Widget'>: save

…which renders:

>>> pxml(form())
<form action="http://example.com/form_action" enctype="multipart/form-data" id="form-demo_form" method="post" novalidate="novalidate">
  <label for="input-demo_form-title">Title</label>
  <div class="field" id="field-demo_form-title">
    <input class="required text" id="input-demo_form-title" name="demo_form.title" required="required" type="text" value="title"/>
  </div>
  <label for="input-demo_form-description">Description</label>
  <div class="field" id="field-demo_form-description">
    <textarea cols="80" id="input-demo_form-description" name="demo_form.description" rows="5">description</textarea>
  </div>
  <input id="input-demo_form-save" name="action.demo_form.save" type="submit" value="Save"/>
</form>
<BLANKLINE>

0.9.1

• add i18n support [rnix, 2011-06-04]

• fix bug where expression evaluation was not reached [rnix, 2011-06-04]

• adopt tests for form novalidate property [rnix, 2011-05-23]

0.9

• make it work [aatis, rnix]