1. Deform: A Form Generation System file:///Users/aclark/Desktop/zpugdc-deformpresentation/slides.html
Deform: A Form Generation System
Authors: Chris McDonough
Agendaless Consulting
Date: 7/6/2010
Features
Generates forms which are capable of capturing complex data structures (lists and mappings,
recursively).
Form validation and errors
AJAX (actually AJAH) forms
Client side field filters (masks for SSN, etc)
Widgets for most common tasks
Comparable To
z3c.form
zope.formlib
ToscaWidgets
Django newforms
Formish (heavily influenced by)
WTForm
Superset Of
Formencode
Notables
Deform not concerned with "model" data. Only with "form" data. The schema you use in
Deform is unrelated to your model's schema.
Compatible with any web framework (or non-framework). No assumptions made about
request/response library, etc.
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2. Deform: A Form Generation System file:///Users/aclark/Desktop/zpugdc-deformpresentation/slides.html
Process
100% statement coverage via unit tests
Each widget has a functional selenium test that uses the application at
http://deformdemo.repoze.org as the application under test.
Well-documented at http://docs.repoze.org/deform.
Dependencies
Colander schema library
Peppercorn form marshalling library
Chameleon templating library
Translationstring i18n library
ISO8601 date parsing library
Generating a Form
This will generate a form with a single text input widget:
import colander, deform
class Schema(colander.Schema):
text = colander.SchemaNode(
colander.String(),
validator=colander.Length(max=100),
description='Enter some text')
schema = Schema()
form = deform.Form(schema, buttons=('submit',))
html = form.render()
Schema Nodes
Schema nodes in a schema can provide:
Its type (string, int, mapping, etc).
A validator function.
The initial value and the "missing" value.
A name, a title, and a description, used during rendering.
Schema nodes are the domain of the Colander package.
Widgets
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3. Deform: A Form Generation System file:///Users/aclark/Desktop/zpugdc-deformpresentation/slides.html
Many prebaked widgets.
1-to-1 relationship between widget and schema node.
Widgets are written in a combination of Python and the Chameleon ZPT templating language
Any other templating language may be used; hook points exist to use a new one.
Different widgets may be used for the same type of schema field (e.g. checkbox vs. radio
choice).
Widgets can be created as necessary.
Widgets are the domain of the Deform package.
Widget Template Example
Here's an example of a widget template that uses Chameleon:
<textarea tal:attributes="rows field.widget.rows;
cols field.widget.cols;"
id="${field.oid}"
name="${field.name}">${cstruct}</textarea>
Validators
Deform ships with a number of prebaked validators for common cases (length, one-of, email-
address, in-range, etc).
New validators can be added.
Validators are the domain of both the Colander and Deform packages.
Validator Example
An example of a Deform validator (return value unimportant):
def is_int(node, value):
try:
int(value)
except (ValueError, OverflowError, TypeError):
raise Invalid(node,
'%r is not a valid integer' %
value)
Edit Forms
Forms allowing you to edit existing data are similar; you just pass in the data structure you'd like to
edit (it must match the schema):
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4. Deform: A Form Generation System file:///Users/aclark/Desktop/zpugdc-deformpresentation/slides.html
import colander, deform
class Schema(colander.Schema):
text = colander.SchemaNode(
colander.String(),
validator=colander.Length(max=100),
description='Enter some text')
schema = Schema()
form = deform.Form(schema, buttons=('submit',))
html = form.render({'text':'Hello!'})
Validation and Re-Rendering
Your code is in charge of doing validation and re-rendering:
# form = deform.Form(schema, buttons=('submit',))
try:
controls = self.request.POST.items()
captured = form.validate(controls)
html = form.render(captured)
except deform.ValidationFailure, e:
# the submitted values could not be validated
html = e.render()
Editing Structure
Often we need to edit or add structure:
"Multi-file" upload widget
Multiple people in a list
Let's see some of that live.
Miscellaneous Features
Internationalization: Deform error messages are internationalizable.
Multiple Forms on the Same Page: possible.
Inter-field Validation: Validator attached to a container node.
AJAX Forms: Built-in.
Input Masks: Built-in.
Futures
Deform is "done".
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5. Deform: A Form Generation System file:///Users/aclark/Desktop/zpugdc-deformpresentation/slides.html
Systems are being built atop Deform (e.g. a "CRUD" system which conflates the model schema
with the form schema).
End
Get it via easy_install deform
Docs at http://docs.repoze.org/deform
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