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

     2 

     3 

     4 Tutoriel : créer votre première application web pour Google AppEngine

     5 =====================================================================

     6 

     7 [TRANSLATE ME TO FRENCH]

     8 

     9 This tutorial will guide you step by step to build a blog application 

    10 and discover the unique features of `LAX`. It assumes that you followed

    11 the :ref:`installation` guidelines and that both the `AppEngine SDK` and the

    12 `LAX` framework are setup on your computer.

    13 

    14 Creating a new application

    15 --------------------------

    16 

    17 We choosed in this tutorial to develop a blog as an example of web application

    18 and will go through each required steps/actions to have it running with `LAX`.

    19 When you installed `LAX`, you saw a directory named ``skel``. Make a copy of

    20 this directory and call it ``BlogDemo``.

    21 

    22 The location of this directory does not matter. But once decided, make sure your ``PYTHONPATH`` is properly set (:ref:`installation`).

    23 

    24 

    25 Defining a schema

    26 -----------------

    27 

    28 With `LAX`, the schema/datamodel is the core of the application. This is where

    29 you will define the type of content you have to hanlde in your application.

    30 

    31 Let us start with something simple and improve on it iteratively. 

    32 

    33 In schema.py, we define two entities: ``Blog`` and ``BlogEntry``.

    34 

    35 ::

    36 

    37   class Blog(EntityType):

    38       title = String(maxsize=50, required=True)

    39       description = String()

    40 

    41   class BlogEntry(EntityType):

    42       title = String(maxsize=100, required=True)

    43       publish_date = Date(default='TODAY')

    44       text = String(fulltextindexed=True)

    45       category = String(vocabulary=('important','business'))

    46       entry_of = SubjectRelation('Blog', cardinality='?*')

    47 

    48 A Blog has a title and a description. The title is a string that is

    49 required by the class EntityType and must be less than 50 characters. 

    50 The description is a string that is not constrained.

    51 

    52 A BlogEntry has a title, a publish_date and a text. The title is a

    53 string that is required and must be less than 100 characters. The

    54 publish_date is a Date with a default value of TODAY, meaning that

    55 when a BlogEntry is created, its publish_date will be the current day

    56 unless it is modified. The text is a string that will be indexed in

    57 the full-text index and has no constraint.

    58 

    59 A BlogEntry also has a relationship ``entry_of`` that link it to a

    60 Blog. The cardinality ``?*`` means that a BlogEntry can be part of

    61 zero or one Blog (``?`` means `zero or one`) and that a Blog can

    62 have any number of BlogEntry (``*`` means `any number including

    63 zero`). For completeness, remember that ``+`` means `one or more`.

    64 

    65 Running the application

    66 -----------------------

    67 

    68 Defining this simple schema is enough to get us started. Make sure you

    69 followed the setup steps described in detail in the installation

    70 chapter (especially visiting http://localhost:8080/_load as an

    71 administrator), then launch the application with the command::

    72 

    73    python dev_appserver.py BlogDemo

    74 

    75 and point your browser at http://localhost:8080/ (if it is easier for

    76 you, use the on-line demo at http://lax.appspot.com/).

    77 

    78 .. image:: images/lax-book.00-login.en.png

    79    :alt: login screen

    80 

    81 After you log in, you will see the home page of your application. It

    82 lists the entity types: Blog and BlogEntry. If these links read

    83 ``blog_plural`` and ``blogentry_plural`` it is because

    84 internationalization (i18n) is not working for you yet. Please ignore

    85 this for now.

    86 

    87 .. image:: images/lax-book.01-start.en.png

    88    :alt: home page

    89 

    90 Creating system entities

    91 ------------------------

    92 You can only create new users if you decided not to use google authentication.

    93 

    94 

    95 [WRITE ME : create users manages permissions etc]

    96 

    97 

    98 

    99 Creating application entites

   100 ----------------------------

   101 

   102 Create a Blog

   103 ~~~~~~~~~~~~~

   104 

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

   106 of the link Blog.  Call this new Blog ``Tech-blog`` and type in

   107 ``everything about technology`` as the description, then validate the

   108 form by clicking on ``Validate``.

   109 

   110 .. image:: images/lax-book.02-create-blog.en.png

   111    :alt: from to create blog

   112 

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

   114 follow the Blog link that will list for you all the existing Blog.

   115 You should be seeing a list with a single item ``Tech-blog`` you

   116 just created.

   117 

   118 .. image:: images/lax-book.03-list-one-blog.en.png

   119    :alt: displaying a list of a single blog

   120 

   121 Clicking on this item will get you to its detailed description except

   122 that in this case, there is not much to display besides the name and

   123 the phrase ``everything about technology``.

   124 

   125 .. image:: images/lax-book.04-detail-one-blog.en.png

   126   :alt: displaying the detailed view of a blog

   127 

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

   129 create a new Blog called ``MyLife`` and get back to the home page

   130 again to follow the Blog link for the second time. The list now

   131 has two items.

   132 

   133 .. image:: images/lax-book.05-list-two-blog.en.png

   134    :alt: displaying a list of two blogs

   135 

   136 

   137 Create a BlogEntry

   138 ~~~~~~~~~~~~~~~~~~

   139 

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

   141 BlogEntry. Call this new entry ``Hello World`` and type in some text

   142 before clicking on ``Validate``. You added a new blog entry without

   143 saying to what blog it belongs. There is a box on the left entitled

   144 ``actions``, click on the menu item ``modify``. You are back to the form

   145 to edit the blog entry you just created, except that the form now has

   146 another section with a combobox titled ``add relation``. Chose

   147 ``entry_of`` in this menu and a second combobox appears where you pick

   148 ``MyLife``. 

   149 

   150 You could also have, at the time you started to fill the form for a

   151 new entity BlogEntry, hit ``Apply`` instead of ``Validate`` and the 

   152 combobox titled ``add relation`` would have showed up.

   153 

   154 .. image:: images/lax-book.06-add-relation-entryof.en.png

   155    :alt: editing a blog entry to add a relation to a blog

   156 

   157 Validate the changes by clicking ``Validate``. The entity BlogEntry

   158 that is displayed now includes a link to the entity Blog named

   159 ``MyLife``.

   160 

   161 .. image:: images/lax-book.07-detail-one-blogentry.en.png

   162    :alt: displaying the detailed view of a blogentry

   163 

   164 Remember that all of this was handled by the framework and that the

   165 only input that was provided so far is the schema. To get a graphical

   166 view of the schema, run the ``laxctl genschema BlogDemo`` command as

   167 explained in the installation section and point your browser to the

   168 URL http://localhost:8080/schema

   169 

   170 .. image:: images/lax-book.08-schema.en.png

   171    :alt: graphical view of the schema (aka data-model)

   172 

   173 Site configuration

   174 ------------------

   175 

   176 .. image:: images/lax-book.03-site-config-panel.en.png

   177 

   178 This panel allows you to configure the appearance of your application site.

   179 Six menus are available and we will go through each of them to explain how

   180 to use them.

   181 

   182 Navigation

   183 ~~~~~~~~~~

   184 This menu provides you a way to adjust some navigation options depending on

   185 your needs, such as the number of entities to display by page of results.

   186 Follows the detailled list of available options:

   187   

   188 * navigation.combobox-limit: maximum number of entities to display in related

   189   combo box (sample format: 23)

   190 * navigation.page-size: maximum number of objects displayed by page of results 

   191   (sample format: 23)

   192 * navigation.related-limit: maximum number of related entities to display in 

   193   the primary view (sample format: 23)

   194 * navigation.short-line-size: maximum number of characters in short description

   195   (sample format: 23)

   196 

   197 UI

   198 ~~

   199 This menu provides you a way to customize the user interface settings such as

   200 date format or encoding in the produced html.

   201 Follows the detailled list of available options:

   202 

   203 * ui.date-format : how to format date in the ui ("man strftime" for format description)

   204 * ui.datetime-format : how to format date and time in the ui ("man strftime" for format

   205   description)

   206 * ui.default-text-format : default text format for rich text fields.

   207 * ui.encoding : user interface encoding

   208 * ui.fckeditor : should html fields being edited using fckeditor (a HTML WYSIWYG editor).

   209   You should also select text/html as default text format to actually get fckeditor.

   210 * ui.float-format : how to format float numbers in the ui

   211 * ui.language : language of the user interface

   212 * ui.main-template : id of main template used to render pages

   213 * ui.site-title	: site title, which is displayed right next to the logo in the header

   214 * ui.time-format : how to format time in the ui ("man strftime" for format description)

   215 

   216 

   217 Actions

   218 ~~~~~~~

   219 This menu provides a way to configure the context in which you expect the actions

   220 to be displayed to the user and if you want the action to be visible or not. 

   221 You must have notice that when you view a list of entities, an action box is 

   222 available on the left column which display some actions as well as a drop-down 

   223 menu for more actions. 

   224 

   225 The context available are:

   226 

   227 * mainactions : actions listed in the left box

   228 * moreactions : actions listed in the `more` menu of the left box

   229 * addrelated : add actions listed in the left box

   230 * useractions : actions listed in the first section of drop-down menu 

   231   accessible from the right corner user login link

   232 * siteactions : actions listed in the second section of drop-down menu

   233   accessible from the right corner user login link

   234 * hidden : select this to hide the specific action

   235 

   236 Boxes

   237 ~~~~~

   238 The application has already a pre-defined set of boxes you can use right away. 

   239 This configuration section allows you to place those boxes where you want in the

   240 application interface to customize it. 

   241 

   242 The available boxes are:

   243 

   244 * actions box : box listing the applicable actions on the displayed data

   245 

   246 * boxes_blog_archives_box : box listing the blog archives 

   247 

   248 * possible views box : box listing the possible views for the displayed data

   249 

   250 * rss box : RSS icon to get displayed data as a RSS thread

   251 

   252 * search box : search box

   253 

   254 * startup views box : box listing the configuration options available for 

   255   the application site, such as `Preferences` and `Site Configuration`

   256 

   257 Components

   258 ~~~~~~~~~~

   259 [WRITE ME]

   260 

   261 Contextual components

   262 ~~~~~~~~~~~~~~~~~~~~~

   263 [WRITE ME]

   264 

   265 Set-up a workflow

   266 -----------------

   267 

   268 Before starting, make sure you refresh your mind by reading [link to

   269 definition_workflow chapter].

   270 

   271 We want to create a workflow to control the quality of the BlogEntry 

   272 submitted on your application. When a BlogEntry is created by a user

   273 its state should be `submitted`. To be visible to all, it needs to

   274 be in the state `published`. To move from `submitted` to `published`

   275 we need a transition that we can name `approve_blogentry`.

   276 

   277 We do not want every user to be allowed to change the state of a 

   278 BlogEntry. We need to define a group of user, `moderators`, and 

   279 this group will have appropriate permissions to approve BlogEntry

   280 to be published and visible to all.

   281 

   282 There are two ways to create a workflow, form the user interface,

   283 and also by defining it in ``migration/postcreate.py``. This script

   284 is executed each time a new ``./bin/laxctl db-init`` is done. 

   285 If you create the states and transitions through the user interface

   286 this means that next time you will need to initialize the database

   287 you will have to re-create all the entities. 

   288 We strongly recommand you create the workflow in ``migration\postcreate.py``

   289 and we will now show you how.

   290 The user interface would only be a reference for you to view the states 

   291 and transitions but is not the appropriate interface to define your

   292 application workflow.

   293 

   294 Update the schema

   295 ~~~~~~~~~~~~~~~~~

   296 To enable a BlogEntry to have a State, we have to define a relation

   297 ``in_state`` in the schema of BlogEntry. Please do as follows, add

   298 the line ``in_state (...)``::

   299 

   300   class BlogEntry(EntityType):

   301       title = String(maxsize=100, required=True)

   302       publish_date = Date(default='TODAY')

   303       text_format = String(meta=True, internationalizable=True, maxsize=50,

   304                            default='text/rest', constraints=[format_constraint])

   305       text = String(fulltextindexed=True)

   306       category = String(vocabulary=('important','business'))

   307       entry_of = SubjectRelation('Blog', cardinality='?*')

   308       in_state = SubjectRelation('State', cardinality='1*')

   309 

   310 As you updated the schema, you will have re-execute ``./bin/laxctl db-init``

   311 to initialize the database and migrate your existing entities.

   312 [WRITE ABOUT MIGRATION]

   313 

   314 Create states, transitions and group permissions

   315 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

   316 

   317 At the time the ``postcreate.py`` script is executed, several methods

   318 can be used. They are all defined in the ``class ServerMigrationHelper``.

   319 We will only discuss the method we use to create a wrokflow here.

   320 

   321 To define our workflow for BlogDemo, please add the following lines

   322 to ``migration/postcreate.py``::

   323   

   324   _ = unicode

   325 

   326   moderators      = add_entity('CWGroup', name=u"moderators")

   327 

   328   submitted = add_state(_('submitted'), 'BlogEntry', initial=True)

   329   published = add_state(_('published'), 'BlogEntry')

   330 

   331   add_transition(_('approve_blogentry'), 'BlogEntry', (submitted,), published, ('moderators', 'managers'),)

   332 

   333   checkpoint()

   334 

   335 ``add_entity`` is used here to define the new group of users that we

   336 need to define the transitions, `moderators`.

   337 If this group required by the transition is not defined before the

   338 transition is created, it will not create the relation `transition 

   339 require the group moderator`.

   340 

   341 ``add_state`` expects as the first argument the name of the state you are

   342 willing to create, then the entity type on which the state can be applied, 

   343 and an optionnal argument to set if the state is the initial state

   344 of the entity type or not.

   345 

   346 ``add_transition`` expects as the first argument the name of the 

   347 transition, then the entity type on which we can apply the transition,

   348 then the list of possible initial states from which the transition

   349 can be applied, the target state of the transition, and the permissions

   350 (e.g. list of the groups of users who can apply the transition).

   351 

   352 .. image:: images/lax-book.03-transitions-view.en.png

   353 

   354 You can now notice that in the actions box of a BlogEntry, the state

   355 is now listed as well as the possible transitions from this state

   356 defined by the workflow. This transition, as defined in the workflow,

   357 will only being displayed for the users belonging to the group

   358 moderators of managers.

   359 

   360 Change view permission

   361 ~~~~~~~~~~~~~~~~~~~~~~

   362 

   363 

   364 

   365 Conclusion

   366 ----------

   367 

   368 Exercise

   369 ~~~~~~~~

   370 

   371 Create new blog entries in ``Tech-blog``.

   372 

   373 What we learned

   374 ~~~~~~~~~~~~~~~

   375 

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

   377 can store blogs and blog entries. 

   378 

   379 What is next ?

   380 ~~~~~~~~~~~~~~

   381 

   382 Although the application is fully functionnal, its look is very

   383 basic. In the following section we will learn to create views to

   384 customize how data is displayed.

   385 

   386