The Registry, selectors and application objects

===============================================

This chapter deals with some of the  core concepts of the |cubicweb| framework

which make it different from other frameworks (and maybe not easy to

grasp at a first glance). To be able to do advanced development with

|cubicweb| you need a good understanding of what is explained below.

This chapter goes deep into details. You don't have to remember them

all but keep it in mind so you can go back there later.

An overview of AppObjects, the VRegistry and Selectors is given in the

:ref:`VRegistryIntro` chapter.

.. autodocstring:: cubicweb.cwvreg

.. autodocstring:: cubicweb.predicates

.. automodule:: cubicweb.appobject

Base predicates

---------------

Predicates are scoring functions that are called by the registry to tell whenever

an appobject can be selected in a given context. Predicates may be chained

together using operators to build a selector. A selector is the glue that tie

views to the data model or whatever input context. Using them appropriately is an

essential part of the construction of well behaved cubes.

Of course you may have to write your own set of predicates as your needs grows

and you get familiar with the framework (see :ref:`CustomPredicates`).

Here is a description of generic predicates provided by CubicWeb that should suit

most of your needs.

Bare predicates

~~~~~~~~~~~~~~~

Those predicates are somewhat dumb, which doesn't mean they're not (very) useful.

.. autoclass:: cubicweb.appobject.yes

.. autoclass:: cubicweb.predicates.match_kwargs

.. autoclass:: cubicweb.predicates.appobject_selectable

.. autoclass:: cubicweb.predicates.adaptable

.. autoclass:: cubicweb.predicates.configuration_values

Result set predicates

~~~~~~~~~~~~~~~~~~~~~

Those predicates are looking for a result set in the context ('rset' argument or

the input context) and match or not according to its shape. Some of these

predicates have different behaviour if a particular cell of the result set is

specified using 'row' and 'col' arguments of the input context or not.

.. autoclass:: cubicweb.predicates.none_rset

.. autoclass:: cubicweb.predicates.any_rset

.. autoclass:: cubicweb.predicates.nonempty_rset

.. autoclass:: cubicweb.predicates.empty_rset

.. autoclass:: cubicweb.predicates.one_line_rset

.. autoclass:: cubicweb.predicates.multi_lines_rset

.. autoclass:: cubicweb.predicates.multi_columns_rset

.. autoclass:: cubicweb.predicates.paginated_rset

.. autoclass:: cubicweb.predicates.sorted_rset

.. autoclass:: cubicweb.predicates.one_etype_rset

.. autoclass:: cubicweb.predicates.multi_etypes_rset

Entity predicates

~~~~~~~~~~~~~~~~~

Those predicates are looking for either an `entity` argument in the input context,

or entity found in the result set ('rset' argument or the input context) and

match or not according to entity's (instance or class) properties.

.. autoclass:: cubicweb.predicates.non_final_entity

.. autoclass:: cubicweb.predicates.is_instance

.. autoclass:: cubicweb.predicates.score_entity

.. autoclass:: cubicweb.predicates.rql_condition

.. autoclass:: cubicweb.predicates.relation_possible

.. autoclass:: cubicweb.predicates.partial_relation_possible

.. autoclass:: cubicweb.predicates.has_related_entities

.. autoclass:: cubicweb.predicates.partial_has_related_entities

.. autoclass:: cubicweb.predicates.has_permission

.. autoclass:: cubicweb.predicates.has_add_permission

.. autoclass:: cubicweb.predicates.has_mimetype

.. autoclass:: cubicweb.predicates.is_in_state

.. autofunction:: cubicweb.predicates.on_fire_transition

.. autoclass:: cubicweb.predicates.implements

Logged user predicates

~~~~~~~~~~~~~~~~~~~~~~

Those predicates are looking for properties of the user issuing the request.

.. autoclass:: cubicweb.predicates.match_user_groups

Web request predicates

~~~~~~~~~~~~~~~~~~~~~~

Those predicates are looking for properties of *web* request, they can not be

used on the data repository side.

.. autoclass:: cubicweb.predicates.no_cnx

.. autoclass:: cubicweb.predicates.anonymous_user

.. autoclass:: cubicweb.predicates.authenticated_user

.. autoclass:: cubicweb.predicates.match_form_params

.. autoclass:: cubicweb.predicates.match_search_state

.. autoclass:: cubicweb.predicates.match_context_prop

.. autoclass:: cubicweb.predicates.match_context

.. autoclass:: cubicweb.predicates.match_view

.. autoclass:: cubicweb.predicates.primary_view

.. autoclass:: cubicweb.predicates.contextual

.. autoclass:: cubicweb.predicates.specified_etype_implements

.. autoclass:: cubicweb.predicates.attribute_edited

.. autoclass:: cubicweb.predicates.match_transition

Other predicates

~~~~~~~~~~~~~~~~

.. autoclass:: cubicweb.predicates.match_exception

.. autoclass:: cubicweb.predicates.debug_mode

You'll also find some other (very) specific predicates hidden in other modules

than :mod:`cubicweb.predicates`.