Problem and Motivation

Behaviors, provided by the plone.behavior package, provide a very useful way of extending the functionality of a Dexterity content type. Unfortunately, the fact that a content type’s behaviors are stored in its factory contents information (FTI) inside the portal_types tool, means that they are class (or type) specific, and not instance specific. This means that behaviors can only be enabled globally, in other words only for all the instances of a specific type.

To enable per instance behaviors, we need a way to store those behaviors on the instance. We use annotations for this purpose.

Additionally, we provide our own IBehaviorAssignable adapter that overrides the default one. It does not only look for an object’s FTI registered annotations, but also look for the behaviors stored in the current instance’s annotations.

Also helper functions are implemented which can be used to dynamically assing behaviors and interfaces on dexterity content objects.

Installation

Depend your plone addon on collective.instancebehavior.

Enable behaviors and interfaces

Note: the targeted object must implement collective.instancebehavior.IInstanceBehaviorAssignableContent.

>>> from plone.app.event.dx.interfaces import IDXEvent
>>> enable_behaviors(
...     obj,
...     ['plone.app.event.dx.behaviors.IEventBasic',],
...     [IDXEvent,]
... )

Disable behaviors and interfaces

>>> from plone.app.event.dx.interfaces import IDXEvent
>>> disable_behaviors(
...     obj,
...     ['plone.app.event.dx.behaviors.IEventBasic',],
...     IDXEvent,]
... )

References

• http://opkode.net/media/blog/plone-and-dexterity-enable-behaviors-per-content-type-instance

• https://gist.github.com/thet/3990769

from IRC

12:13 < rnix> datakurre: https://github.com/bluedynamics/bda.plone.productshop/blob/master/bda/plone/productshop/browser/forms.py
12:13 < rnix> datakurre: woring instance behavior enabled add form
12:21 < rnix> datakurre: may be generalized to collective.instancebehavior -> just need a generic way on telling DX to use the correct form. -> idea would be to have a
              behavior which can be bound to folderish objects and this defined default behaviors applied dynamically
12:21 < rnix> to it's direct children
12:22 < rnix> but i do not really like to register this add view for every type.. would be more appropriate if we found a way on
12:22 < rnix> deciding by applied container interface
12:22 < rnix> something like that...
12:26 < datakurre> rnix: What the differences for original add form? 1) show fields for default instance behaviors 2) enable default instance behaviors on save?
12:28 < datakurre> rnix: 2) Could probably be done by instancebehavior-adapter (add form would call it, when instancebehavior-behavior is enabled)
12:28 < datakurre> rnix: 1) migth be possible with plone.z3cform's FormExtender
12:30 < rnix> datakurre: i was thinking of an IChildDefaultInstanceBehaviors behavior, which reads the available IInstanceBehavior deriving definitions. and sets them to
              all added children by default
12:30 < rnix> the add view can then be bound to IChildDefaultInstanceBehaviors
12:31 < datakurre> rnix: Well, that works for sure.
12:32 < rnix> datakurre: instead of binding the add view by name to Products.CMFCore.interfaces.IFolderish, we bind it to IChildDefaultInstanceBehaviors without name...

Source Code

The sources are in a GIT DVCS with its main branches at github. There you can report issue too.

We’d be happy to see many forks and pull-requests to make this addon even better.

This package uses the black code style.

Contributors

• JC Brand

• Johannes Raggam

• Robert Niederreiter

• Peter Holzer

• Jens Klein

0.5

• Invalidate global schema cache [jensens]

• Black code style, isort imports, overall housekeeping [jensens]

0.4

• Be more explicit on dependencies and other egg improvements [tomgross]

0.3

• Fix DexterityInstanceBehaviorAssignable.enumerateBehaviors in order to work with plone.dexterity >= 2.3.0 [agitator]

0.2

• convert behaviors in enable_behaviors to tuple before concat. [rnix]

• check whether instance behavior already in instance_behaviors before adding. [rnix]

0.1

• created collective.instancebehavior based on jcbrand’s and thet’s work [rnix]

• improved implementation with generic helper functions [thet]

• problem description and initial implementation [jcbrand]