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archetypes.schemaextender 2.1.8

Dynamically extend Archetypes schemas with named adapters.


This package allows you to modify an Archetypes schema, using simple adapters. This can be used to add new fields, reorder fields and fieldsets or make other changes.

The most common use of schema extension is to allow add-on products to enhance standard Plone content types, for example by adding an option that can be set to toggle special behaviour.

schemaextender hooks into the Archetypes framework by registering an ISchema adapter for BaseContent and BaseFolder, making it responsible for providing the schema for all types derived from those classes. This includes all standard Plone content types. Since only one ISchema adapter can be active schemaextender provides its own mechanism to modify schemas using named adapters. Named adapters are allowing to register more than one schemaextender per adapted interface.

There are three types of adapters available:

  • ISchemaExtender: using this adapter you can add new fields to a schema.
  • IOrderableSchemaExtender: this adapters makes it possible to both add new fields and reorder fields. This is more costly than just adding new fields.
  • IBrowserLayerAwareExtender: this adapters are making use of plone.browserlayer, so that the extender is only available if a layer is registered.
  • ISchemaModifier: this is a low-level hook that allows direct manipulation of the schema. This can be very dangerous and should never be used if one does not know exactly what she/he is doing!

The adapter types are documented in the ”” file in archetypes.schemaextender.

Simple example

As an example we will add a simple boolean field to the standard Plone document type. First we need to create a field class:

from Products.Archetypes.public import BooleanField
from archetypes.schemaextender.field import ExtensionField

class MyBooleanField(ExtensionField, BooleanField):
    """A trivial field."""

schemaextender can not use the standard Archetypes fields directly since those rely on the class generation logic generating accessors and mutator methods. By using the ExtensionField mix-in class we can still use them. Make sure the ExtensionField mix-in comes first, so it properly overwrites the standard methods.

Next we have to create an adapter that will add this field:

from zope.component import adapts
from zope.interface import implements
from archetypes.schemaextender.interfaces import ISchemaExtender
from Products.Archetypes.public import BooleanWidget
from Products.ATContentTypes.interfaces import IATDocument

class PageExtender(object):

    fields = [
        widget = BooleanWidget(
            label="This page has super powers")),

    def __init__(self, context):
        self.context = context

    def getFields(self):
        return self.fields

Try to store the fields on the class, that way they aren’t created each time the getFields method gets called. Generally you should make sure getFields does as few things as possible, because it’s called very often.

The final step is registering this adapter with the Zope component architecture. Since we already declared the interface we provide and which type of object we adapt this can be done very quickly in configure.zcml (assuming you put the code above in a file

<configure xmlns=""

    <include package="archetypes.schemaextender" />
    <adapter factory=".extender.PageExtender" />

Custom fields

If you want you can make more complicated field types as well. The only requirement is that you need to have ExtensionField as the first parent class for your field type. As an example here is a field that toggles a marker interface on an object:

from zope.interface import Interface
from zope.interface import alsoProvides
from zope.interface import noLongerProvides
from Products.Archetypes.public import BooleanField
from archetypes.schemaextender.field import ExtensionField

def addMarkerInterface(obj, *ifaces):
    for iface in ifaces:
        if not iface.providedBy(obj):
            alsoProvides(obj, iface)

def removeMarkerInterface(obj, *ifaces):
    for iface in ifaces:
        if iface.providedBy(obj):
            noLongerProvides(obj, iface)

class ISuperPower(Interface):
    """Marker interface for classes that can do amazing things."""

class InterfaceMarkerField(ExtensionField, BooleanField):
    def get(self, instance, **kwargs):
        return ISuperPower.providedBy(instance)

    def getRaw(self, instance, **kwargs):
        return ISuperPower.providedBy(instance)

    def set(self, instance, value, **kwargs):
        if value:
            addMarkerInterface(instance, ISuperPower)
            removeMarkerInterface(instance, ISuperPower)

Layer-aware example

By using archetypes.schemaextender.IBrowserLayerAwareExtender the extender is only applied if a specific browser layer is installed on the site.


You should always use IBrowserLayerAwareExtender on configurations where there can be multiple Plone sites on a single Zope application server. Otherwise extenders are applied on every site, unconditionally.

Below is an example of which adds new field on Dates edit tab:


    Retrofit re-review dates to Archetypes schema.


__docformat__ = "epytext"

from zope.component import adapts
from zope.interface import implements

from Products.Archetypes.public import BooleanWidget
from Products.ATContentTypes.interfaces import IATDocument
from Products.Archetypes import public as atapi
from Products.Archetypes.interfaces import IBaseContent

from archetypes.schemaextender.field import ExtensionField
from archetypes.schemaextender.interfaces import (
  ISchemaExtender, IOrderableSchemaExtender, IBrowserLayerAwareExtender)

# Your add-on browserlayer
from your.package.interfaces import IAddOnInstalled

class ExtensionDateField(ExtensionField, atapi.DateTimeField):
    """ Retrofitted date field """

class RevisitExtender(object):
    """ Include revisit date on all objects.

    An example extended which will create a new field on Dates
    tab between effective date and expiration date.

    # This extender will apply to all Archetypes based content

    # We use both orderable and browser layer aware sensitive properties
    implements(IOrderableSchemaExtender, IBrowserLayerAwareExtender)

    # Don't do schema extending unless our add-on product is installed on Plone site
    layer = IAddOnInstalled

    fields = [
            widget = atapi.CalendarWidget(
                label="Review Date",
                description=(u"When this date is reached, the content "
                             u"will be visible in the review task list"),

    def __init__(self, context):
        self.context = context

    def getOrder(self, schematas):
        """ Manipulate the order in which fields appear.

        @param schematas: Dictonary of schemata name -> field lists

        @return: Dictionary of reordered field lists per schemata.
        schematas["dates"] = ['effectiveDate', 'revisitDate', 'expirationDate',
                              'creation_date', 'modification_date']

        return schematas

    def getFields(self):
        @return: List of new fields we contribute to content.
        return self.fields

Note: since the above example has two interfaces in its implements line, you will get an error when your Zope instance starts up:

TypeError: Missing 'provides' attribute

This means we need to be more explicit in our zcml configuration and specify which of the two interfaces is provided by our adapter:

<adapter factory=".extender.RevisitExtender"
    provides="archetypes.schemaextender.interfaces.ISchemaExtender" />


2.1.8 (2018-01-30)

Bug fixes:

  • Add Python 2 / 3 compatibility. [maurits]

2.1.7 (2017-03-09)

Bug fixes:

  • Update docs about Products.ATContentTypes.interfaces import location. [thet]
  • Fix imports from Globals that was removed in Zope4 [pbauer]

2.1.6 (2016-08-11)


  • Use zope.interface decorator. [gforcada]

2.1.5 (2015-03-11)

  • Ported tests to

2.1.4 (2014-09-08)

2.1.3 (2014-02-26)

  • Fix tests [kiorky]

2.1.2 (2013-01-13)

  • PEP8 changes, documentation updates. [maurits]

2.1.1 - 2011-07-04

  • Acquire request object via local site hook if object is not acquisition-wrapped (in cachingInstanceSchemaFactory). This fixes caching issues with objects rendered using DTML. Note that this is likely a bug in the DocumentTemplate code. Ideally, the issue should be resolved there. [malthe]

2.1 - 2011-01-03

  • Use plone.uuid to look up content UUIDs. [toutpt, davisagli]
  • Added example of how to use ordered extenders and browser layer aware extenders. [miohtama]

2.0.3 - 2010-07-07

  • Added back the caching.zcml file, but have it load configure.zcml. This makes it easier to write Plone 3 / 4 compatible code. [hannosch]
  • Factored out the condition to disable the cache during tests into a module global variable called CACHE_ENABLED. [hannosch]

2.0.2 - 2010-06-13

  • Changed the schema cache again, to use the id() only as a fallback when there is not yet an UID assigned. The id() is unstable with Acquisition wrappers and ZODB level ghosting of objects. We provide an explicit API for disabling the cache instead. [hannosch]
  • Avoid deprecation warnings under Zope 2.13. [hannosch]
  • Change the schema cache key to avoid an issue during content migration when there might be two objects that have the same UID but different schemata. Now concatenating the Python id() with the UID (id() alone isn’t good enough, as two objects with non-overlapping lifetimes may have the same id() value). Fixes [davisagli]

2.0.1 - 2010-05-23

  • Disable the schema cache during test runs. [hannosch]

2.0 - 2010-05-23

  • Removed the caching.zcml and enabled caching by default. You can use a different caching implementation by using an overrides.zcml file. [hannosch]
  • Added z3c.autoinclude entry point to mark this as a Plone plugin. [hannosch]

1.6 - 2010-03-22

  • Fix index accessor to support setting custom accessor methods. [witsch]

1.5 - 2009-11-18

  • Fixed test failure in usage.txt. [hannosch]
  • Standardized package metadata layout. [hannosch]

1.4 - 2009-11-05

  • Fix schema copying to also include properties and layers. [maerteijn]

1.3 - 2009-10-20

  • Refactored the TranslatableExtensionField getMutator to directly reuse the generatedMutatorWrapper from LinguaPlone itself. This avoids duplicating the logic and lets schemaextender fields use the special reference field handling introduced in LinguaPlone. This change introduces a version requirement for LinguaPlone of at least 3.0b6. [hannosch]

1.2 - 2009-10-10

  • Add ISchema adapter using simple caching on the request in order to avoid redundant calculation of the (extended) schema. The adapter is not enabled by default and can be activated by loading caching.zcml. [witsch]
  • Avoid using the overridden + operator when copying the original schema as this will needlessly validate all fields again. [witsch]
  • Added missing changelog entry. [hannosch, woutervh]

1.1 - 2009-06-03

  • Added support for LinguaPlone language independent fields, by seamlessly using a new TranslatableExtensionField when LP is installed. [hannosch]
  • Added a proper interface to the IExtensionField. [hannosch]
  • Adjusted tests for Plone 3.3. [hannosch]
  • Minor adjustment in documentation: a) don’t adapt the class in the example, b) explain why named adapters are used. [jensens]
  • Schema modifiers now also browserlayer-aware. [jessesnyder]

1.0 - 2008-07-17

  • No changes since 1.0rc1.

1.0rc1 - 2008-04-07

  • Added optional plone.browserlayer support. Extenders implementing IBrowserLayerAwareExtender need to have a layer attribute. Those extenders are taken into account only if the specified layer is active. [jensens]

1.0b1 - 2007-12-07

  • Schema modifiers implementing ISchemaModifier are now responsible for copying fields they modify. See README and the doc strings. [fschulze]
  • Added a simple benchmark and made some optimizations by avoiding a lot of field copying. [fschulze, wiggy]
  • Use a marker interface instead of overrides.zcml - this means you don’t need to muck with overrides in dependent products. [optilude]
  • Added code to allow addition of new schemata. We need an ordered dictionary to not bork the order of the schemata. [jensens]
  • Add a small benchmark utility. [wichert]
  • Replace the high-level test with unit-tests and extend the test coverage. [wichert]
  • Rewrite the README to be more human readable. [wichert]

1.0a1 - 2007-10-15

  • First public release.
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