The VRegistry, 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.selectors

.. automodule:: cubicweb.appobject

Base selectors

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

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

an appobject can be selected in a given context. Selector sets are for instance

the glue that tie views to the data model. 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 selectors as your needs grows and

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

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

most of your needs.

Bare selectors

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

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

.. autoclass:: cubicweb.appobject.yes

.. autoclass:: cubicweb.selectors.match_kwargs

.. autoclass:: cubicweb.selectors.appobject_selectable

.. autoclass:: cubicweb.selectors.adaptable

.. autoclass:: cubicweb.selectors.configuration_values

Result set selectors

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

Those selectors 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

selectors 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.selectors.none_rset

.. autoclass:: cubicweb.selectors.any_rset

.. autoclass:: cubicweb.selectors.nonempty_rset

.. autoclass:: cubicweb.selectors.empty_rset

.. autoclass:: cubicweb.selectors.one_line_rset

.. autoclass:: cubicweb.selectors.multi_lines_rset

.. autoclass:: cubicweb.selectors.multi_columns_rset

.. autoclass:: cubicweb.selectors.paginated_rset

.. autoclass:: cubicweb.selectors.sorted_rset

.. autoclass:: cubicweb.selectors.one_etype_rset

.. autoclass:: cubicweb.selectors.multi_etypes_rset

Entity selectors

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

Those selectors 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.selectors.non_final_entity

.. autoclass:: cubicweb.selectors.is_instance

.. autoclass:: cubicweb.selectors.score_entity

.. autoclass:: cubicweb.selectors.rql_condition

.. autoclass:: cubicweb.selectors.relation_possible

.. autoclass:: cubicweb.selectors.partial_relation_possible

.. autoclass:: cubicweb.selectors.has_related_entities

.. autoclass:: cubicweb.selectors.partial_has_related_entities

.. autoclass:: cubicweb.selectors.has_permission

.. autoclass:: cubicweb.selectors.has_add_permission

.. autoclass:: cubicweb.selectors.has_mimetype

.. autoclass:: cubicweb.selectors.is_in_state

.. autofunction:: cubicweb.selectors.on_fire_transition

.. autoclass:: cubicweb.selectors.implements

Logged user selectors

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

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

.. autoclass:: cubicweb.selectors.anonymous_user

.. autoclass:: cubicweb.selectors.authenticated_user

.. autoclass:: cubicweb.selectors.match_user_groups

Web request selectors

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

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

used on the data repository side.

.. autoclass:: cubicweb.selectors.match_form_params

.. autoclass:: cubicweb.selectors.match_search_state

.. autoclass:: cubicweb.selectors.match_context_prop

.. autoclass:: cubicweb.selectors.match_view

.. autoclass:: cubicweb.selectors.primary_view

.. autoclass:: cubicweb.selectors.specified_etype_implements

.. autoclass:: cubicweb.selectors.attribute_edited

Other selectors

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

.. autoclass:: cubicweb.selectors.match_transition

.. autoclass:: cubicweb.selectors.debug_mode

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

than :mod:`cubicweb.selectors`.