cubicweb: comparison doc/book/en/tutorials/base/customizing-the-application.rst

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-.. -*- 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

changeset 10491	c67bcee93248
parent 10490	76ab3c71aff2
child 10492	68c13e0c0fc5