1. Cube creation and schema definition#

1.1. Step 1: creating a virtual environment#

Fisrt I need a python virtual environment with cubicweb:

python3 -m venv venv
source venv/bin/activate
pip install cubicweb

1.2. Step 2: creating a new cube for my web site#

One note about my development environment: I wanted to use the packaged version of CubicWeb and cubes while keeping my cube in the current directory, let’s say ~/src/cubes:

cd ~/src/cubes
CW_MODE=user

I can now create the cube which will hold custom code for this web site using:

cubicweb-ctl newcube sytweb

Enter a short description and this will create your new cube in the cubicweb-sytweb folder.

1.3. Step 3: pick building blocks into existing cubes#

Almost everything I want to handle in my web-site is somehow already modelized in existing cubes that I’ll extend for my need. So I’ll pick the following cubes:

folder, containing the Folder entity type, which will be used as both ‘album’ and a way to map file system folders. Entities are added to a given folder using the filed_under relation.
file, containing File entity type, gallery view, and a file system import utility.
person, containing the Person entity type plus some basic views.
comment, providing a full commenting system allowing one to comment entity types supporting the comments relation by adding a Comment entity.
tag, providing a full tagging system as an easy and powerful way to classify entities supporting the tags relation by linking the to Tag entities. This will allows navigation into a large number of picture.

Ok, now I’ll tell my cube requires all this by editing cubicweb-sytweb/cubicweb_sytweb/__pkginfo__.py:

__depends__ = {'cubicweb': '>= 3.32.7',
               'cubicweb-file': '>= 1.9.0',
               'cubicweb-folder': '>= 1.1.0',
               'cubicweb-person': '>= 1.2.0',
               'cubicweb-comment': '>= 1.2.0',
               'cubicweb-tag': '>= 1.2.0'
               }

Notice that you can express minimal version of the cube that should be used, None meaning whatever version available. All packages starting with ‘cubicweb-’ will be recognized as being cube, not bare python packages.

Now, I need to install all the dependencies:

cd cubicweb-sytweb
pip install -e .
pip install cubicweb
pip install psycopg2-binary # for postgresql

1.4. Step 4: glue everything together in my cube’s schema#

Put this code in cubicweb-sytweb/cubicweb_sytweb/schema.py:

from yams.buildobjs import RelationDefinition


class comments(RelationDefinition):
    subject = 'Comment'
    object = 'File'
    # a Comment can be on only one File
    # but a File can have several comments
    cardinality = '1*'
    composite = 'object'


class tags(RelationDefinition):
    subject = 'Tag'
    object = 'File'


class filed_under(RelationDefinition):
    subject = 'File'
    object = 'Folder'


class displayed_on(RelationDefinition):
    subject = 'Person'
    object = 'File'

This schema:

allows to comment and tag on File entity type by adding the comments and tags relations. This should be all we’ve to do for this feature since the related cubes provide ‘pluggable section’ which are automatically displayed on the primary view of entity types supporting the relation.
adds a situated_in relation definition so that image entities can be geolocalized.
add a new relation displayed_on relation telling who can be seen on a picture.

This schema will probably have to evolve as time goes (for security handling at least), but since the possibility to let a schema evolve is one of CubicWeb’s features (and goals), we won’t worry about it for now and see that later when needed.

1.5. Step 5: creating the instance#

Now that I have a schema, I want to create an instance. To do so using this new ‘sytweb’ cube, I run:

cubicweb-ctl create sytweb sytweb_instance

For simplicity you should use the sqlite database, it won’t require configuration.

Don’t forget to say “yes” to the question: Allow anonymous access ? [y/N]:

Hint: if you get an error while the database is initialized, you can avoid having to answer the questions again by running:

cubicweb-ctl db-create sytweb_instance

This will use your already configured instance and start directly from the create database step, thus skipping questions asked by the ‘create’ command.

Once the instance and database are fully initialized, run

cubicweb-ctl pyramid -D sytweb_instance

to start the instance, check you can connect on it, etc… then go on http://localhost:8080 (or with another port if you’ve modified it)

Cube creation and schema definition

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