.. -*- coding: utf-8 -*-

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LAX Tutorial

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Introduction

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

LAX is a web framework on top of the Google AppEngine datastore.

features: schema/data-model at core of app, selection/view mechanism,

reuseable components, very fast development

Since we are french, let us develop an example application that deals

with wine and will allow any wine enthusiast to track the content of

its cellar and share his tasting experiences.

Schema

------

With LAX, the core of the application is the schema/datamodel.

laxctl newapp ? XXX

We will start by something simple and define three entities: WineMaker,

Wine and Bottle.

::

  class WineMaker(EntityType):

      name = String(maxsize=50, required=True)

  class Wine(EntityType):

      name = String(required=True, maxsize=100, fulltextindexed=True)

      vintage = Int(required=True, constraints=[IntervalBoundConstraint(1850,2100)])

      grown_by = SubjectRelation('WineMaker', cardinality='?*',

                                 description=_('Winemaker who grew the wine'))

  class Bottle(EntityType):

      buy_date = Date(description=_('Date when the bottle was bought.'),

                      default='TODAY')

      bottle_of = SubjectRelation('Wine', cardinality='?*')

A WineMaker only has a name which is a string that is required and

must be less than 50 characters.

A Wine has a name, which is a string that is required, must be less

than 100 characters and will be indexed in the full-text index XXX

fulltextindex marche pas encore. A Wine

also has a vintage year which is an integer that is required and must

be between 1850 and 2100. A Wine also has a relationship ``grown_by``

that link it to a WineMaker. Cardinality ``?*`` means that a Wine can

have zero or one WineMaker (``?`` means `zero or one`) and that a

WineMaker can have any number of Wine entities (``*`` means `any number

including zero`).

A Bottle has a buy_date attribute, which is a date with a default

value of TODAY, meaning that when a new bottle is created, it will

have its creation date as buy_date unless the user changes it to some

other date. A Bottle also has a relationship ``bottle_of`` that link

it to a Wine. The cardinality of that relationship implies that a

Bottle can be linked to zero or one Wine and that a Wine can by linked

to any number of Bottle entities.

Defining this simple schema is enough to get us started, launch the

application with the command::

   laxctl start Winopedia

and point your browser at localhost:8080

You will see the home page of your application. It lists the entity

types: WineMaker, Wine, Bottle.

Let us create a few of these. Click on the [+] at the right of the

link WineMaker. Call this new WineMaker ``Domaine du château`` and

validate the form by clicking on ``button_ok``. 

Click on the logo at top left to get back to the home page, then

follow the WineMaker link. You should be seeing a list with a single

item ``Domaine du château``. Clicking on this item will get you to 

its detailed description except that in this case, there is not much

to display besides the name.

Now get back to the home page by clicking on the top-left logo, then

create a new WineMaker called ``Vallon de la Dame`` and get back to the

home page again to follow the WineMaker link for the second time. The

list now has two items.

Get back to the home page and click on [+] at the right of the link

Wine. Call this new wine ``Cuvée du Roi`` and enter 2008 as vintage,

then click on ``button_ok``. You added a new wine without saying who

made it. There is a box on the left entitled "actions", click on the

menu item `modify`. You are back to the form to edit the wine entity

you just created, except that the form now has another section with a

combobox titled "add a relationship". Chose "grown_by" in this

menu and a second combobox appears where you pick ``Domaine du

château``. Validate the changes by clicking  ``button_ok``. The entity

Wine that is displayed now includes a link to the entity WineMaker

named ``Domaine du château``.

Exercise

~~~~~~~~

Create new entities Wine and Bottle.

What we learned

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

Creating a simple schema was enough to set up a new application that

can store WineMaker, Wine, Bottle. 

What is next ?

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

Althought the application is fully functionnal, its look is very

basic. We will now improve how information is displayed by writing

views.

Views

======

...

Defining views with selection/views

implementing interfaces, calendar for bottles bought and for tasting.

calendar with export icalput attribute drink_date on bottle 

add attribute wine color

create view "bottle table" with color, buy_date, drink_date.

in view wine, select Wine.bottles and apply view "bottle table"

demo ajax with filter on bottle table

Components

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...

customize MainTemplate

rss channel of new bottles or wines

use URLRewriting for nice urls

talk about security access rights

talk about rql