plone.autoform

Contents

• plone.autoform
  • Introduction
  • Basic schema-based forms
  • Controlling form presentation
    • Changing a field's display mode
    • Omitting fields
    • Re-ordering fields
    • Organizing fields into fieldsets
    • Changing a field's widget
    • Protect a field with a permission
  • Display Forms
  • Behind the scenes: how autoform directives work
• Source Code

Introduction

plone.autoform builds custom z3c.form forms based on a model (schema) of what fields to include and what widgets and options should be used for each field. This model is defined as a zope.schema-based schema, but additional hints can be supplied to control aspects of form display not normally specified in a Zope schema.

Basic schema-based forms

To use the automatic form setup, mix in the following base class in your forms:

>>> from plone.autoform.form import AutoExtensibleForm

and then provide the schema (a schema interface) and optionally the additionalSchemata (a list of schema interfaces) attributes on your form:

class MyForm(AutoExtensibleForm, form.EditForm):
    schema = IMySchema
    additionalSchemata = (ISchemaOne, ISchemaTwo,)
    # ...

For dynamic forms, you could of course make schema and additionalSchemata into properties. For example, plone.dexterity extends the basic AutoExtensibleForm so that schema is the content type schema and additionalSchemata is a list of field provider schemas associated with behaviors.

Controlling form presentation

Directives can be specified in the schema to control aspects of form presentation.

Changing a field's display mode

A field's widget can be displayed in several "modes":

• input - allows the user to enter data into the field
• display - a read-only indication of the field's value
• hidden - a record of the field's value that is included only in the HTML source

The mode can be controlled using the mode directive:

from plone.supermodel import model
from plone.autoform import directives as form

class IMySchema(model.Schema):

    form.mode(secret='hidden')
    form.mode(IEditForm, secret='input')
    secret = schema.TextLine(
        title=u"Secret",
        default=u"Secret stuff (except on edit forms)"
        )

In this case the mode for the secret field is set to 'hidden' for most forms, but 'input' for forms that provide the IEditForm interface.

The corresponding supermodel XML directive is form:mode:

<field type="zope.schema.TextLine"
        name="secret"
        form:mode="z3c.form.interfaces.IForm:hidden z3c.form.interfaces.IEditForm:input">
    <title>Secret</title>
    <description>Secret stuff (except on edit forms)</description>
</field>

The mode can be specified briefly if it should be the same for all forms:

<field type="zope.schema.TextLine"
        name="secret"
        form:mode="hidden">
    <title>Secret</title>
    <description>Secret stuff</description>
</field>

In other words, form:mode may be either a single mode, or a space-separated list of form_interface:mode pairs.

Omitting fields

A field can be omitted entirely from all forms, or from some forms, using the omitted and no_omit directives. In this example, the dummy field is omitted from all forms, and the edit_only field is omitted from all forms except those that provide the IEditForm interface:

from z3c.form.interfaces import IEditForm
from plone.supermodel import model
from plone.autoform import directives as form

class IMySchema(model.Schema):

    form.omitted('dummy')
    dummy = schema.Text(
        title=u"Dummy"
        )

    form.omitted('edit_only')
    form.no_omit(IEditForm, 'edit_only')
    edit_only = schema.TextLine(
        title = u'Only included on edit forms',
        )

In supermodel XML, this can be specified as:

<field type="zope.schema.TextLine"
       name="dummy"
       form:omitted="true">
    <title>Dummy</title>
</field>

<field type="zope.schema.TextLine"
       name="edit-only"
       form:omitted="z3c.form.interfaces.IForm:true z3c.form.interfaces.IEditForm:false">
    <title>Only included on edit form</title>
</field>

form:omitted may be either a single boolean value, or a space-separated list of form_interface:boolean pairs.

Re-ordering fields

A field's position in the form can be influenced using the order_before and order_after directives. In this example, the not_last field is placed before the summary field even though it is defined afterward:

from plone.supermodel import model
from plone.autoform import directives as form

class IMySchema(model.Schema):

    summary = schema.Text(
        title=u"Summary",
        description=u"Summary of the body",
        readonly=True
        )

    form.order_before(not_last='summary')
    not_last = schema.TextLine(
        title=u"Not last",
        )

The value passed to the directive may be either '*' (indicating before or after all fields) or the name of another field. Use '.fieldname' to refer to field in the current schema or a base schema. Prefix with the schema name (e.g. 'IDublinCore.title') to refer to a field in another schema. Use an unprefixed name to refer to a field in the current or the default schema for the form.

In supermodel XML, the directives are called form:before and form:after. For example:

<field type="zope.schema.TextLine"
       name="not_last"
       form:before="*">
    <title>Not last</title>
</field>

Organizing fields into fieldsets

Fields can be grouped into fieldsets, which will be rendered within an HTML <fieldset> tag. In this example the footer and dummy fields are placed within the extra fieldset:

from plone.supermodel import model
from plone.autoform import directives as form

class IMySchema(model.Schema):

    model.fieldset('extra',
        label=u"Extra info",
        fields=['footer', 'dummy']
        )

    footer = schema.Text(
        title=u"Footer text",
        )

    dummy = schema.Text(
        title=u"Dummy"
        )

In supermodel XML fieldsets are specified by grouping fields within a <fieldset> tag:

<fieldset name="extra" label="Extra info">
    <field name="footer" type="zope.schema.TextLine">
        <title>Footer text</title>
    </field>
    <field name="dummy" type="zope.schema.TextLine">
        <title>Dummy</title>
    </field>
</fieldset>

Changing a field's widget

Usually, z3c.form picks a widget based on the type of your field. You can change the widget using the widget directive if you want users to enter or view data in a different format. For example, here we change the widget for the human field to use yes/no radio buttons instead of a checkbox:

from plone.supermodel import model
from plone.autoform import directives as form
from z3c.form.browser.radio import RadioFieldWidget

class IMySchema(model.Schema):
    form.widget('human', RadioFieldWidget)
    human = schema.Bool(
        title = u'Are you human?',
        )

You can also pass widget parameters to control attributes of the widget. For example, here we keep the default widget, but set a CSS class:

from plone.supermodel import model
from plone.autoform import directives as form
from z3c.form.browser.radio import RadioWidget

class IMySchema(model.Schema):
    form.widget('human', klass='annoying')
    human = schema.Bool(
        title = u'Are you human?',
        )

In supermodel XML the widget is specified using a <form:widget> tag, which can have its own elements specifying parameters:

<field name="human" type="zope.schema.TextLine">
    <title>Are you human?</title>
    <form:widget type="z3c.form.browser.radio.RadioWidget">
        <klass>annoying</klass>
    </form:widget>
</field>

Note: In order to be included in the XML representation of a schema, widget parameters must be handled by a WidgetExportImportHandler utility. There is a default one which handles the attributes defined in z3c.form.browser.interfaces.IHTMLFormElement.

Protect a field with a permission

By default, fields are included in the form regardless of the user's permissions. Fields can be protected using the read_permission and write_permission directives. The read permission is checked when the field is in display mode, and the write permission is checked when the field is in input mode. The permission should be given with its Zope 3-style name (i.e. cmf.ManagePortal rather than 'Manage portal').

In this example, the secret field is protected by the cmf.ManagePortal permission as both a read and write permission. This means that in both display and input modes, the field will only be included in the form for users who have that permission:

from plone.supermodel import model
from plone.autoform import directives as form

class IMySchema(model.Schema):
    form.read_permission(secret='cmf.ManagePortal')
    form.write_permission(secret='cmf.ManagePortal')
    secret = schema.TextLine(
        title = u'Secret',
        )

In supermodel XML the directives are security:read-permission and security:write-permission:

<field type="zope.schema.TextLine"
       name="secret"
       security:read-permission="cmf.ManagePortal"
       security:write-permission="cmf.ManagePortal">
    <title>Secret</title>
</field>

Display Forms

Sometimes rather than rendering a form for data entry, you want to display stored values based on the same schema. This can be done using a "display form." The display form renders each field's widget in "display mode," which means that it shows the field value in read-only form rather than as a form input.

To use the display form, create a view that extends WidgetsView like this:

>>> from plone.autoform.view import WidgetsView
>>> class MyView(WidgetsView):
...     schema = IMySchema
...     additionalSchemata = (ISchemaOne, ISchemaTwo,)
...
...     # ...

To render the form, do not override __call__(). Instead, either implement the render() method, set an index attribute to a page template or other callable, or use the template attribute of the <browser:page /> ZCML directive when registering the view.

In the template, you can use the following variables:

• view/w is a dictionary of all widgets, including those from non-default fieldsets (by contrast, the widgets variable contains only those widgets in the default fieldset). The keys are the field names, and the values are widget instances. To render a widget (in display mode), you can do tal:replace="structure view/w/myfield/render" />.
• view/fieldsets is a dictionary of all fieldsets (not including the default fieldset, i.e. those widgets not placed into a fieldset). They keys are the fieldset names, and the values are the fieldset form instances, which in turn have variables like widgets given a list of all widgets.

Behind the scenes: how autoform directives work

Zope schema fields do not allow storing arbitrary key-value data associated with a particular field. However, arbitrary data can be stored in a dictionary on the schema (interface) known as the "tagged values." This is where plone.autoform keeps track of its extra hints, whether they are configured via Python directives, an XML model, or some other way.

The tagged values are stored under various keys, which are defined in the plone.autoform.interfaces module. They can be set several ways:

• Manually, by using setTaggedValue() on an interface.
• By loading the schema from a plone.supermodel XML file and using the form: prefix
• By using the directives from plone.autoform.directives while defining a schema in Python.

Source Code

Contributors please read the document Process for Plone core's development

Sources are at the Plone code repository hosted at Github.