Form schema hints¶

Directives which can be used to configure forms from schemata

Dexterity uses the plone.autoform package to configure its z3c.form-based add and edit forms. This allows a schema to be annotated with “form hints”, which are used to configure the form.

The easiest way to apply form hints in Python code is to use the directives from plone.directives.form and plone.directives.dexterity. These directives are used when the package is “grokked” (via the <grok:grok package=“.” />*ZCML directive) to apply the form hints to the interface where they are found. For this process to work, the schema must derive from *plone.directives.form.Schema. Directives can be placed anywhere in the class body. By convention they are kept next to the fields they apply to.

For example, here is a schema that omits a field:

                      from plone.directives import form
from zope import schema

class ISampleSchema(form.Schema):

    title = schema.TextLine(title=u"Title")

    form.omitted('additionalInfo')
    additionalInfo = schema.Bytes()

The form directives take parameters in the form of a list of field names, or a set of field name/value pairs as keyword arguments. Each directive can be used zero or more times.

Form directives¶

The form directives in the plone.directives.form package are shown below.

Name	Description
widget	Specify an alternate widget for a field. Pass the field name as a key and a widget as the value. The widget can either be a z3c.form widget instance or a string giving the dotted name to one.
omitted	Omit one or more fields from forms. Takes a sequence of field names as parameters.
mode	Set the widget mode for one or more fields. Pass the field name as a key and the string ‘input’, ‘display’ or ‘hidden’ as the value.
order_before	Specify that a given field should be rendered before another. Pass the field name as a key and name of the other field as a value. If the other field is in a supplementary schema (i.e. one from a behaviour), its name will be e.g. “IOtherSchema.otherFieldName”. Alternatively, pass the string “*” to put a field first in the form.
order_after	The inverse of order_before(), putting a field after another. Passing “*” will put the field at the end of the form.
primary	Designate a given field as the primary field in the schema. This is not used for form rendering, but is used for WebDAV marshaling of the content object.
fieldset	Creates a fieldset (rendered in Plone as a tab on the edit form).

The code sample below illustrates each of these directives:

                        from plone.directives import form
from zope import schema
from plone.app.z3cform.wysiwyg import WysiwygFieldWidget

class ISampleSchema(form.Schema):

    # A fieldset with id 'extra' and label 'Extra information' containing
    # the 'footer' and 'dummy' fields. The label can be omitted if the
    # fieldset has already been defined.

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

    # Here a widget is specified as a dotted name.
    # The body field is also designated as the priamry field for this schema

    form.widget(body='plone.app.z3cform.wysiwyg.WysiwygFieldWidget')
    form.primary('body')
    body = schema.Text(
            title=u"Body text",
            required=False,
            default=u"Body text goes here"
        )

    # The widget can also be specified as an object

    form.widget(footer=WysiwygFieldWidget)
    footer = schema.Text(
            title=u"Footer text",
            required=False
        )

    # An omitted field. Use form.omitted('a', 'b', 'c') to omit several fields

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

    # A field in 'hidden' mode

    form.mode(secret='hidden')
    secret = schema.TextLine(
            title=u"Secret",
            default=u"Secret stuff"
        )

    # This field is moved before the 'description' field of the standard
    # IBasic behaviour, if this is in use.

    form.order_before(importantNote='IBasic.description')
    importantNote = schema.TextLine(
            title=u"Important note",
        )

                      

Security directives¶

The security directives in the plone.directives.dexterity package are shown below. Note that these are also used to control reading and writing of fields on content instances.

Name	Description
read_permission	Set the (Zope 3) name of a permission required to read the field’s value. Pass the field name as a key and the permission name as a string value. Among other things, this controls the field’s appearance in display forms.
write_permission	Set the (Zope 3) name of a permission required to write the field’s value. Pass the field name as a key and the permission name as a string value. Among other things, this controls the field’s appearance in add and edit forms.

The code sample below illustrates each of these directives:

                        from plone.directives import form, dexterity
from zope import schema

class ISampleSchema(form.Schema):

    # This field requires the 'cmf.ReviewPortalContent' to be read and
    # written

    dexterity.read_permission(reviewNotes='cmf.ReviewPortalContent')
    dexterity.write_permission(reviewNotes='cmf.ReviewPortalContent')
    reviewNotes = schema.Text(
            title=u"Review notes",
            required=False,
        )

                      