--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/doc/tutorials/base/customizing-the-application.rst Thu Jan 08 22:11:06 2015 +0100
@@ -0,0 +1,539 @@
+.. -*- coding: utf-8 -*-
+
+.. _TutosBaseCustomizingTheApplication:
+
+Customizing your application
+----------------------------
+
+So far so good. The point is that usually, you won't get enough by assembling
+cubes out-of-the-box. You will want to customize them, have a personal look and
+feel, add your own data model and so on. Or maybe start from scratch?
+
+So let's get a bit deeper and start coding our own cube. In our case, we want
+to customize the blog we created to add more features to it.
+
+
+Create your own cube
+~~~~~~~~~~~~~~~~~~~~
+
+First, notice that if you've installed |cubicweb| using Debian packages, you will
+need the additional ``cubicweb-dev`` package to get the commands necessary to
+|cubicweb| development. All `cubicweb-ctl` commands are described in details in
+:ref:`cubicweb-ctl`.
+
+Once your |cubicweb| development environment is set up, you can create a new
+cube::
+
+ cubicweb-ctl newcube myblog
+
+This will create in the cubes directory (:file:`/path/to/grshell/cubes` for source
+installation, :file:`/usr/share/cubicweb/cubes` for Debian packages installation)
+a directory named :file:`blog` reflecting the structure described in
+:ref:`cubelayout`.
+
+For packages installation, you can still create new cubes in your home directory
+using the following configuration. Let's say you want to develop your new cubes
+in `~src/cubes`, then set the following environment variables: ::
+
+ CW_CUBES_PATH=~/src/cubes
+
+and then create your new cube using: ::
+
+ cubicweb-ctl newcube --directory=~/src/cubes myblog
+
+.. Note::
+
+ We previously used `myblog` as the name of our *instance*. We're now creating
+ a *cube* with the same name. Both are different things. We'll now try to
+ specify when we talk about one or another, but keep in mind this difference.
+
+
+Cube metadata
+~~~~~~~~~~~~~
+
+A simple set of metadata about your cube are stored in the :file:`__pkginfo__.py`
+file. In our case, we want to extend the blog cube, so we have to tell that our
+cube depends on this cube, by modifying the ``__depends__`` dictionary in that
+file:
+
+.. sourcecode:: python
+
+ __depends__ = {'cubicweb': '>= 3.10.7',
+ 'cubicweb-blog': None}
+
+where the ``None`` means we do not depends on a particular version of the cube.
+
+.. _TutosBaseCustomizingTheApplicationDataModel:
+
+Extending the data model
+~~~~~~~~~~~~~~~~~~~~~~~~
+
+The data model or schema is the core of your |cubicweb| application. It defines
+the type of content your application will handle. It is defined in the file
+:file:`schema.py` of the cube.
+
+
+Defining our model
+******************
+
+For the sake of example, let's say we want a new entity type named `Community`
+with a name, a description. A `Community` will hold several blogs.
+
+.. sourcecode:: python
+
+ from yams.buildobjs import EntityType, RelationDefinition, String, RichString
+
+ class Community(EntityType):
+ name = String(maxsize=50, required=True)
+ description = RichString()
+
+ class community_blog(RelationDefinition):
+ subject = 'Community'
+ object = 'Blog'
+ cardinality = '*?'
+ composite = 'subject'
+
+The first step is the import from the :mod:`yams` package necessary classes to build
+the schema.
+
+This file defines the following:
+
+* a `Community` has a title and a description as attributes
+
+ - the name is a string that is required and can't be longer than 50 characters
+
+ - the description is a string that is not constrained and may contains rich
+ content such as HTML or Restructured text.
+
+* a `Community` may be linked to a `Blog` using the `community_blog` relation
+
+ - ``*`` means a community may be linked to 0 to N blog, ``?`` means a blog may
+ be linked to 0 to 1 community. For completeness, remember that you can also
+ use ``+`` for 1 to N, and ``1`` for single, mandatory relation (e.g. one to one);
+
+ - this is a composite relation where `Community` (e.g. the subject of the
+ relation) is the composite. That means that if you delete a community, its
+ blog will be deleted as well.
+
+Of course, there are a lot of other data types and things such as constraints,
+permissions, etc, that may be defined in the schema, but those won't be covered
+in this tutorial.
+
+Notice that our schema refers to the `Blog` entity type which is not defined
+here. But we know this type is available since we depend on the `blog` cube
+which is defining it.
+
+
+Applying changes to the model into our instance
+***********************************************
+
+Now the problem is that we created an instance using the `blog` cube, not our
+`myblog` cube, so if we don't do anything there is no way that we'll see anything
+changing in the instance.
+
+One easy way, as we've no really valuable data in the instance would be to trash and recreated it::
+
+ cubicweb-ctl stop myblog # or Ctrl-C in the terminal running the server in debug mode
+ cubicweb-ctl delete myblog
+ cubicweb-ctl create myblog
+ cubicweb-ctl start -D myblog
+
+Another way is to add our cube to the instance using the cubicweb-ctl shell
+facility. It's a python shell connected to the instance with some special
+commands available to manipulate it (the same as you'll have in migration
+scripts, which are not covered in this tutorial). In that case, we're interested
+in the `add_cube` command: ::
+
+ $ cubicweb-ctl stop myblog # or Ctrl-C in the terminal running the server in debug mode
+ $ cubicweb-ctl shell myblog
+ entering the migration python shell
+ just type migration commands or arbitrary python code and type ENTER to execute it
+ type "exit" or Ctrl-D to quit the shell and resume operation
+ >>> add_cube('myblog')
+ >>>
+ $ cubicweb-ctl start -D myblog
+
+The `add_cube` command is enough since it automatically updates our
+application to the cube's schema. There are plenty of other migration
+commands of a more finer grain. They are described in :ref:`migration`
+
+As explained, leave the shell by typing Ctrl-D. If you restart the instance and
+take another look at the schema, you'll see that changes to the data model have
+actually been applied (meaning database schema updates and all necessary stuff
+has been done).
+
+.. image:: ../../images/tutos-base_myblog-schema_en.png
+ :alt: the instance schema after adding our cube
+
+If you follow the 'info' link in the user pop-up menu, you'll also see that the
+instance is using blog and myblog cubes.
+
+.. image:: ../../images/tutos-base_myblog-siteinfo_en.png
+ :alt: the instance schema after adding our cube
+
+You can now add some communities, link them to blog, etc... You'll see that the
+framework provides default views for this entity type (we have not yet defined any
+view for it!), and also that the blog primary view will show the community it's
+linked to if any. All this thanks to the model driven interface provided by the
+framework.
+
+You'll then be able to redefine each of them according to your needs
+and preferences. We'll now see how to do such thing.
+
+.. _TutosBaseCustomizingTheApplicationCustomViews:
+
+Defining your views
+~~~~~~~~~~~~~~~~~~~
+
+|cubicweb| provides a lot of standard views in directory
+:file:`cubicweb/web/views/`. We already talked about 'primary' and 'list' views,
+which are views which apply to one ore more entities.
+
+A view is defined by a python class which includes:
+
+ - an identifier: all objects used to build the user interface in |cubicweb| are
+ recorded in a registry and this identifier will be used as a key in that
+ registry. There may be multiple views for the same identifier.
+
+ - a *selector*, which is a kind of filter telling how well a view suit to a
+ particular context. When looking for a particular view (e.g. given an
+ identifier), |cubicweb| computes for each available view with that identifier
+ a score which is returned by the selector. Then the view with the highest
+ score is used. The standard library of predicates is in
+ :mod:`cubicweb.predicates`.
+
+A view has a set of methods inherited from the :class:`cubicweb.view.View` class,
+though you usually don't derive directly from this class but from one of its more
+specific child class.
+
+Last but not least, |cubicweb| provides a set of default views accepting any kind
+of entities.
+
+Want a proof? Create a community as you've already done for other entity types
+through the index page, you'll then see something like that:
+
+.. image:: ../../images/tutos-base_myblog-community-default-primary_en.png
+ :alt: the default primary view for our community entity type
+
+
+If you notice the weird messages that appear in the page: those are messages
+generated for the new data model, which have no translation yet. To fix that,
+we'll have to use dedicated `cubicweb-ctl` commands:
+
+.. sourcecode: bash
+
+ cubicweb-ctl i18ncube myblog # build/update cube's message catalogs
+ # then add translation into .po file into the cube's i18n directory
+ cubicweb-ctl i18ninstance myblog # recompile instance's message catalogs
+ cubicweb-ctl restart -D myblog # instance has to be restarted to consider new catalogs
+
+You'll then be able to redefine each of them according to your needs and
+preferences. So let's see how to do such thing.
+
+Changing the layout of the application
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The layout is the general organization of the pages in the site. Views that generate
+the layout are sometimes referred to as 'templates'. They are implemented in the
+framework in the module :mod:`cubicweb.web.views.basetemplates`. By overriding
+classes in this module, you can customize whatever part you wish of the default
+layout.
+
+But notice that |cubicweb| provides many other ways to customize the
+interface, thanks to actions and components (which you can individually
+(de)activate, control their location, customize their look...) as well as
+"simple" CSS customization. You should first try to achieve your goal using such
+fine grained parametrization rather then overriding a whole template, which usually
+embeds customisation access points that you may loose in the process.
+
+But for the sake of example, let's say we want to change the generic page
+footer... We can simply add to the module ``views`` of our cube,
+e.g. :file:`cubes/myblog/views.py`, the code below:
+
+.. sourcecode:: python
+
+ from cubicweb.web.views import basetemplates
+
+ class MyHTMLPageFooter(basetemplates.HTMLPageFooter):
+
+ def footer_content(self):
+ self.w(u'This website has been created with <a href="http://cubicweb.org">CubicWeb</a>.')
+
+ def registration_callback(vreg):
+ vreg.register_all(globals().values(), __name__, (MyHTMLPageFooter,))
+ vreg.register_and_replace(MyHTMLPageFooter, basetemplates.HTMLPageFooter)
+
+
+* Our class inherits from the default page footer to ease getting things right,
+ but this is not mandatory.
+
+* When we want to write something to the output stream, we simply call `self.w`,
+ which *must be passed a unicode string*.
+
+* The latest function is the most exotic stuff. The point is that without it, you
+ would get an error at display time because the framework wouldn't be able to
+ choose which footer to use between :class:`HTMLPageFooter` and
+ :class:`MyHTMLPageFooter`, since both have the same selector, hence the same
+ score... In this case, we want our footer to replace the default one, so we have
+ to define a :func:`registration_callback` function to control object
+ registration: the first instruction tells to register everything in the module
+ but the :class:`MyHTMLPageFooter` class, then the second to register it instead
+ of :class:`HTMLPageFooter`. Without this function, everything in the module is
+ registered blindly.
+
+.. Note::
+
+ When a view is modified while running in debug mode, it is not required to
+ restart the instance server. Save the Python file and reload the page in your
+ web browser to view the changes.
+
+We will now have this simple footer on every page of the site.
+
+
+Primary view customization
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The 'primary' view (i.e. any view with the identifier set to 'primary') is the one used to
+display all the information about a single entity. The standard primary view is one
+of the most sophisticated views of all. It has several customisation points, but
+its power comes with `uicfg`, allowing you to control it without having to
+subclass it.
+
+However this is a bit off-topic for this first tutorial. Let's say we simply want a
+custom primary view for my `Community` entity type, using directly the view
+interface without trying to benefit from the default implementation (you should
+do that though if you're rewriting reusable cubes; everything is described in more
+details in :ref:`primary_view`).
+
+
+So... Some code! That we'll put again in the module ``views`` of our cube.
+
+.. sourcecode:: python
+
+ from cubicweb.predicates import is_instance
+ from cubicweb.web.views import primary
+
+ class CommunityPrimaryView(primary.PrimaryView):
+ __select__ = is_instance('Community')
+
+ def cell_call(self, row, col):
+ entity = self.cw_rset.get_entity(row, col)
+ self.w(u'<h1>Welcome to the "%s" community</h1>' % entity.printable_value('name'))
+ if entity.description:
+ self.w(u'<p>%s</p>' % entity.printable_value('description'))
+
+What's going on here?
+
+* Our class inherits from the default primary view, here mainly to get the correct
+ view identifier, since we don't use any of its features.
+
+* We set on it a selector telling that it only applies when trying to display
+ some entity of the `Community` type. This is enough to get an higher score than
+ the default view for entities of this type.
+
+* View applying to entities usually have to define `cell_call` as entry point,
+ and are given `row` and `col` arguments tell to which entity in the result set
+ the view is applied. We can then get this entity from the result set
+ (`self.cw_rset`) by using the `get_entity` method.
+
+* To ease thing, we access our entity's attribute for display using its
+ printable_value method, which will handle formatting and escaping when
+ necessary. As you can see, you can also access attributes by their name on the
+ entity to get the raw value.
+
+
+You can now reload the page of the community we just created and see the changes.
+
+.. image:: ../../images/tutos-base_myblog-community-custom-primary_en.png
+ :alt: the custom primary view for our community entity type
+
+We've seen here a lot of thing you'll have to deal with to write views in
+|cubicweb|. The good news is that this is almost everything that is used to
+build higher level layers.
+
+.. Note::
+
+ As things get complicated and the volume of code in your cube increases, you can
+ of course still split your views module into a python package with subpackages.
+
+You can find more details about views and selectors in :ref:`Views`.
+
+
+Write entities to add logic in your data
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+|cubicweb| provides an ORM to easily programmaticaly manipulate
+entities (just like the one we have fetched earlier by calling
+`get_entity` on a result set). By default, entity
+types are instances of the :class:`AnyEntity` class, which holds a set of
+predefined methods as well as property automatically generated for
+attributes/relations of the type it represents.
+
+You can redefine each entity to provide additional methods or whatever you want
+to help you write your application. Customizing an entity requires that your
+entity:
+
+- inherits from :class:`cubicweb.entities.AnyEntity` or any subclass
+
+- defines a :attr:`__regid__` linked to the corresponding data type of your schema
+
+You may then want to add your own methods, override default implementation of some
+method, etc...
+
+.. sourcecode:: python
+
+ from cubicweb.entities import AnyEntity, fetch_config
+
+
+ class Community(AnyEntity):
+ """customized class for Community entities"""
+ __regid__ = 'Community'
+
+ fetch_attrs, cw_fetch_order = fetch_config(['name'])
+
+ def dc_title(self):
+ return self.name
+
+ def display_cw_logo(self):
+ return 'CubicWeb' in self.description
+
+In this example:
+
+* we used convenience :func:`fetch_config` function to tell which attributes
+ should be prefetched by the ORM when looking for some related entities of this
+ type, and how they should be ordered
+
+* we overrode the standard `dc_title` method, used in various place in the interface
+ to display the entity (though in this case the default implementation would
+ have had the same result)
+
+* we implemented here a method :meth:`display_cw_logo` which tests if the blog
+ entry title contains 'CW'. It can then be used when you're writing code
+ involving 'Community' entities in your views, hooks, etc. For instance, you can
+ modify your previous views as follows:
+
+.. sourcecode:: python
+
+
+ class CommunityPrimaryView(primary.PrimaryView):
+ __select__ = is_instance('Community')
+
+ def cell_call(self, row, col):
+ entity = self.cw_rset.get_entity(row, col)
+ self.w(u'<h1>Welcome to the "%s" community</h1>' % entity.printable_value('name'))
+ if entity.display_cw_logo():
+ self.w(u'<img src="http://www.cubicweb.org/doc/en/_static/cubicweb.png"/>')
+ if entity.description:
+ self.w(u'<p>%s</p>' % entity.printable_value('description'))
+
+Then each community whose description contains 'CW' is shown with the |cubicweb|
+logo in front of it.
+
+.. Note::
+
+ As for view, you don't have to restart your instance when modifying some entity
+ classes while your server is running in debug mode, the code will be
+ automatically reloaded.
+
+
+Extending the application by using more cubes!
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+One of the goal of the |cubicweb| framework was to have truly reusable
+components. To do so, they must both behave nicely when plugged into the
+application and be easily customisable, from the data model to the user
+interface. And I think the result is pretty successful, thanks to system such as
+the selection mechanism and the choice to write views as python code which allows
+to build our page using true object oriented programming techniques, that no
+template language provides.
+
+
+A library of standard cubes is available from `CubicWeb Forge`_, to address a
+lot of common concerns such has manipulating people, files, things to do, etc. In
+our community blog case, we could be interested for instance in functionalities
+provided by the `comment` and `tag` cubes. The former provides threaded
+discussion functionalities, the latter a simple tag mechanism to classify content.
+Let's say we want to try those. We will first modify our cube's :file:`__pkginfo__.py`
+file:
+
+.. sourcecode:: python
+
+ __depends__ = {'cubicweb': '>= 3.10.7',
+ 'cubicweb-blog': None,
+ 'cubicweb-comment': None,
+ 'cubicweb-tag': None}
+
+Now, we'll simply tell on which entity types we want to activate the 'comment'
+and 'tag' facilities by adding respectively the 'comments' and 'tags' relations on
+them in our schema (:file:`schema.py`).
+
+.. sourcecode:: python
+
+ class comments(RelationDefinition):
+ subject = 'Comment'
+ object = 'BlogEntry'
+ cardinality = '1*'
+ composite = 'object'
+
+ class tags(RelationDefinition):
+ subject = 'Tag'
+ object = ('Community', 'BlogEntry')
+
+
+So in the case above we activated comments on `BlogEntry` entities and tags on
+both `Community` and `BlogEntry`. Various views from both `comment` and `tag`
+cubes will then be automatically displayed when one of those relations is
+supported.
+
+Let's synchronize the data model as we've done earlier: ::
+
+
+ $ cubicweb-ctl stop myblog
+ $ cubicweb-ctl shell myblog
+ entering the migration python shell
+ just type migration commands or arbitrary python code and type ENTER to execute it
+ type "exit" or Ctrl-D to quit the shell and resume operation
+ >>> add_cubes(('comment', 'tag'))
+ >>>
+
+Then restart the instance. Let's look at a blog entry:
+
+.. image:: ../../images/tutos-base_myblog-blogentry-taggable-commentable-primary_en.png
+ :alt: the primary view for a blog entry with comments and tags activated
+
+As you can see, we now have a box displaying tags and a section proposing to add
+a comment and displaying existing one below the post. All this without changing
+anything in our views, thanks to the design of generic views provided by the
+framework. Though if we take a look at a community, we won't see the tags box!
+That's because by default this box try to locate itself in the left column within
+the white frame, and this column is handled by the primary view we
+hijacked. Let's change our view to make it more extensible, by keeping both our
+custom rendering but also extension points provided by the default
+implementation.
+
+
+.. sourcecode:: python
+
+ class CommunityPrimaryView(primary.PrimaryView):
+ __select__ = is_instance('Community')
+
+ def render_entity_title(self, entity):
+ self.w(u'<h1>Welcome to the "%s" community</h1>' % entity.printable_value('name'))
+
+ def render_entity_attributes(self, entity):
+ if entity.display_cw_logo():
+ self.w(u'<img src="http://www.cubicweb.org/doc/en/_static/cubicweb.png"/>')
+ if entity.description:
+ self.w(u'<p>%s</p>' % entity.printable_value('description'))
+
+It appears now properly:
+
+.. image:: ../../images/tutos-base_myblog-community-taggable-primary_en.png
+ :alt: the custom primary view for a community entry with tags activated
+
+You can control part of the interface independently from each others, piece by
+piece. Really.
+
+
+
+.. _`CubicWeb Forge`: http://www.cubicweb.org/project