Jesse Vincent > Jifty-0.70824 > Jifty::Manual::Tutorial

Download:
Jifty-0.70824.tar.gz

Annotate this POD

CPAN RT

New  13
Open  4
Stalled  1
View/Report Bugs
Source   Latest Release: Jifty-1.10518

NAME ^

Jifty::Manual::Tutorial - Zero to Jifty in a Jiffy

DESCRIPTION ^

This tutorial should give you everything you need to build your first application with Jifty.

HOW TO ^

The requirements

Here's what you need to have installed -- at least when we write it.

Installing Jifty

No bones about it. We believe pretty strongly in the DRY (Don't Repeat Yourself) principle. That's one of the big reasons we love Perl and CPAN. Jifty makes use of lots of amazing code from CPAN. At last count, it directly depended on 60 packages from CPAN. Most of these libraries are cross-platform pure-Perl packages and should run great out of the box on any platform you can get Perl onto.

We've gone to lengths to make sure you don't spend your day downloading library after library by bundling everything we can inside the Jifty package. The Jifty installer is capable of determining what modules your system needs, and downloading and installing them all in one go. Don't worry, it will ask you first before it makes any changes.

On most systems you can use Perl's bundled CPAN module to download and install Jifty:

  # perl -MCPAN -e"install Jifty"

If you've downloaded a .tar.gz of Jifty, you can do a manual install:

  # tar xzvf jifty-<version>.tgz
  # cd jifty-<version>
  # perl Makefile.PL
  # make
  # make test
  # make install

If the tests don't pass, we want to hear about it. Please join us on jifty-devel@lists.jifty.org and report the failure. (See "GETTING HELP" below for info on how to join the list.)

Setting up the Scaffolding

Once you have Jifty happily installed, you're ready to create your first application.

Jifty is intentionally a bit minimalist. All you really need to make an application go is a copy of the jifty commandline tool (inside your new application's bin/ directory.)

Of course, it's often helpful to have a bit more structure around to help guide your work. Jifty comes with tools to build that structure for you.

Change directory to some place it will be safe to create a new Jifty application. (Jifty will create a subdirectory for you).

  # jifty app --name MyWeblog
  Can't guess application root from current path (/tmp) or bin path (/usr/bin)
  Creating new application MyWeblog
  Creating directory lib
  Creating directory lib/MyWeblog
  Creating directory bin
  Creating directory etc
  Creating directory doc
  Creating directory log
  Creating directory var
  Creating directory var/mason
  Creating directory share
  Creating directory share/po
  Creating directory share/web
  Creating directory share/web/templates
  Creating directory share/web/static
  Creating directory lib/MyWeblog/Model
  Creating directory lib/MyWeblog/Action
  Creating directory t
  Creating configuration file MyWeblog/etc/config.yml

Let's take those one by one.

bin

Inside bin/ is jifty, the Jifty command dispatcher. Some of the most important commands are schema, which sets up or updates your database schema and server, which starts a standalone webserver. To find out what commands your jifty comes with, run:

    jifty help
etc

Configuration files live in etc/, though if you don't have a config file, Jifty will supply some sane defaults.

doc

Jifty won't magically write your documentation for you, but when you write your docs, put them in doc/.

log

Jifty uses Log::Log4perl to configure its logging. By default, it dumps logs named server.log and error.log into the log directory.

share/web/templates

Jifty uses HTML::Mason as its primary templating system. Put your application's templates into share/web/templates/. Out of the box, Jifty comes with an application skeleton that it installs in share/web/templates/. This default application is a convenient way to get a basic application up and running quickly, but probably needs some customization as you build a more advanced application.

You can find where Perl stuck Jifty's default templates with:

  perl -MJifty::Util -e 'print Jifty::Util->share_root'
share/web/static

Some nontrivial percentage of the stuff your web application serves out doesn't need to (or shouldn't) pass through your templating engine.

Just drop your static files into share/web/static/ and Jifty will serve them out if it can't find a template with the right name.

Out of the box, Jifty comes with a CSS style, Javascript libraries and a Pony. Look in share/web/static in the Jifty distribution, or in the same place Jifty stuck its default templates.

lib/MyWeblog

For a full treatment of the Jifty object model see Jifty::Manual::ObjectModel.

To build a basic Jifty application, you only need to worry about two sorts of classes, Models and Actions.

lib/MyWeblog/Model

The real base of your application lives in lib/ApplicationName/Model. Classes here define your application's data structures and how they relate to each other. Jifty will use your model classes to set up and upgrade your database's schema when it needs to.

lib/MyWeblog/Action

When we said you only need to worry about Models and Actions, we weren't telling the whole truth. Jifty will take care of basic database-interaction (CREATE, READ, UPDATE, DELETE) Actions for your Models, but they're there if you want to change anything.

t

Jifty starts off your application with a basic harness, but can't yet write all your tests for you. (It does, however, build simple tests for model classes you generate.)

var

Jifty stores cache files here while the server is running. You shouldn't ever have to touch this directory.

Building your data model

As you might imagine by the fact that this tutorial application is named MyWeblog, the example here is a simple weblog application. Future tutorials will add authentication, comments, and RSS and Atom feeds.

Posts

Weblogs tend to center around posts, so it's no surprise that the first model to create is the post:

  # cd MyWeblog
  # jifty model --name Post
  Writing file /tmp/MyWeblog/t/00-model-Post.t
  Writing file /tmp/MyWeblog/lib/MyWeblog/Model/Post.pm

Great! Now you have a Post model (not that it models anything yet).

Open lib/MyWeblog/Model/Post.pm in your favorite text editor.

You should see something like this:

  use strict;
  use warnings;
  
  package MyWeblog::Model::Post;
  use Jifty::DBI::Schema;
  
  use MyWeblog::Record schema {
  
  };
  
  # Your model-specific methods go here.
  
  1;

Now it's time to tell the model class about posts. Start by giving our post a body and a title. (In a future tutorial, the application will become fully folksonomy-compliant by adding a category and upgrading that category to a tags table.)

Position your cursor right after:

  use MyWeblog::Record schema {

Add the lines:

  column title =>
        type is 'text',
        label is 'Title',
        default is 'Untitled post';

  column body => 
        type is 'text',
        label is 'Content',
        render_as 'Textarea';

Save your model class.

Setting up the database

Ok. It's time to initialize MyWeblog's database. By default, Jifty sets up your application with the SQLite database engine. If you'd rather use PostgreSQL or MySQL, you need to add some content to etc/config.yml. (See Jifty::Config for a bit more information).

  # jifty schema --setup
  INFO - Generating SQL for application MyWeblog...
  INFO - Using MyWeblog::Model::Post
  INFO - Using Jifty::Model::Session
  INFO - Using Jifty::Model::Metadata
  INFO - Using Jifty::Model::Schema
  INFO - Set up version v0.0.1, jifty version 0.607280

Starting the Jifty application server

Ok. You have a working, if simplistic, application. Start up a webserver and have a look around. Be sure to check out the AJAX-enabled administrative UI, the online documentation browser, and the Pony.

  # ./bin/jifty server
  INFO - You can connect to your server at http://localhost:8888/

Please always run this command at the root directory of your Jifty applications, or you'll be caught by a lot of errors.

For many platforms, a simple "jifty server" command works too. :)

Building a user interface

The administrative web does give you everything you need to work with your application's data, but it's not much of a weblog.

Posting

Create a page to post a new weblog entry:

  # cd share/web/templates/

Open a new file called post in your text editor. Make it look like this:

  <%init>
  my $action = Jifty->web->new_action(class => 'CreatePost');
  </%init>

  <&| /_elements/wrapper, title => "Post to your weblog" &>
  <% Jifty->web->form->start() %>
  <% Jifty->web->form->next_page( url => '/') %>
  <% $action->form_field('title') %>
  <% $action->form_field('body') %>
  <% Jifty->web->form->submit( label => 'Post' ) %>
  <% Jifty->web->form->end() %>
  </&>

Yes, it's a template file in HTML::Mason syntax. If you're not familiar with Mason, we recommend you to consult its online documentation for details. Mason templates should start in the first column of the file. Particularly importantly, the <%init> and </%init> blocks must be flush left.

Viewing

It's really easy to get a basic listing of entries and a little bit more complex to get a pretty AJAXified paged list. Here's how to do both; you can decide which one works best for you.

(If you cut and paste the code in the examples below, make sure it's lined up in column 1, or it won't work.)

The quick and dirty way

Open a new file called index.html in the share/web/templates directory in your text editor. (Your webserver will treat the URL /index.html as the default page for your site). Make it look like this:

  <%init>
  my $posts = MyWeblog::Model::PostCollection->new();
  $posts->unlimit();
  </%init>

  <&| /_elements/wrapper, title => Jifty->config->framework('ApplicationName') &>
  <dl>
  % while (my $post = $posts->next) {
   <dt><% $post->title %></dt>
   <dd><% $post->body %></dd>
  % }
  </dl>
  </&>

(Make sure to remove that leading whitespace!)

The complex way that gets you lots of cool toys

The complex way involves using one of Jifty's advanced features: Page regions. These regions let your application reload page sections independently, either using AJAX on modern high-end browsers or regular GET requests with downlevel browsers such as lynx, w3m, or the browser on your mobile phone.

The downside of this approach is that each separate region needs to live in its own fragment file.

The complex way starts off about the same as the easy way. Open a new file called share/web/templates/index.html in your text editor. Fill it with this:

  <&| /_elements/wrapper, title => Jifty->config->framework('ApplicationName') &>

  <% Jifty->web->region(name => "myweblog-posts",
                        path => "/fragments/page_of_posts") %>
  </&>

If you're on the ball, you've probably already guessed that you need to create a file called share/web/templates/fragments/page_of_posts containing:

  <%args>
  $page => 1
  </%args>
  <%init>
  my $posts = MyWeblog::Model::PostCollection->new();
  $posts->unlimit();
  $posts->set_page_info( current_page => $page,
                         per_page     => 15
                       );
  $m->out("No items found.") if ($posts->pager->total_entries == 0);

  </%init>
  % if ($posts->pager->last_page > 1) {
     Page <% $page %> of <% $posts->pager->last_page %>
  % }
  <dl class="list">
  % while (my $post = $posts->next) {
   <dt><% $post->title %></dt>
   <dd><% $post->body %></dd>
  % }
  </dl>

  % if ($posts->pager->previous_page) {
    <% Jifty->web->link( label => "Previous Page", onclick => { args => { page => $posts->pager->previous_page } } ) %>
  % }
  % if ($posts->pager->next_page) {
    <% Jifty->web->link( label => "Next Page", onclick => { args => { page => $posts->pager->next_page } } ) %>
  % }

Now fire up your Jifty webserver again. Go create a post by browsing /post on your webserver. Create more than 15 posts, and notice how Jifty gives you AJAX Next Page and Previous Page buttons for you. Turn off javascript or view the page in lynx, and notice how the AJAX automatically falls-back to page loads for you. All for free, thanks to Jifty!

Hey, where'd that class come from?

If you're paying attention, you may have wondered about MyWeblog::Model::PostCollection, since there's no file called PostCollection.pm. By default, Jifty uses Jifty::ClassLoader to auto-generate a bunch of classes for you. Of course, you can override these definitions if you like. See Jifty::ClassLoader for more details.

Navigation

Of course, having to remember the URL to get to the posting page is a bit annoying. To get a Post button in the menu, you need to override the default menus.

Jifty's default menus live in _elements/nav in the default application template (along with the Pony). For now, override _elements/nav. (We're working on ways to make this better.)

Inside your applications share/web/templates directory, create a directory called _elements.

  mkdir share/web/templates/_elements

You may want to start with the stock jifty template, in which case you only need to add the $top->child( Post... part

  cat $(perl -MJifty::Util -e 'print Jifty::Util->share_root' \
    )/web/templates/_elements/nav > share/web/templates/_elements/nav

Otherwise, inside _elements, open up a new file called nav in your text editor and insert:

  <%init>
  my $top = Jifty->web->navigation;
  $top->child( Home => url => "/");
  $top->child( Post => url => "/post", 
                       label => "Post Article");
  </%init>

For more information about the menu system, see the documentation in Jifty::Web::Menu.

That's it!

That's just about everything you need to get started building Jifty applications. We're working hard to make Jifty even easier to use and to obsolete the hard bits of this tutorial as quickly as we can.

Please join us on the jifty-devel mailing list to talk about how you're using Jifty or what you find difficult or hard to use about it.

GETTING HELP ^

Online Help

The jifty command-line application comes with builtin help.

  jifty help

  jifty help <command>

If your server is running with administration mode enabled (the configuration file AdminMode setting is missing or non-zero), you can click the "Online Docs" link in your browser for an extensive list of per-module Jifty documentation.

Joining the mailing list

jifty-devel@lists.jifty.org is where we discuss how we're building Jifty, what we're having trouble with and so on.

To join the list, send mail to jifty-devel-subscribe@lists.jifty.org.

Browsing the wiki

We have a wiki! (Actually, the wiki is Jifty's primary website)

Please visit http://jifty.org/, browse and contribute.

The wiki is powered by Wifty, a Wiki built on Jifty. Its code is freely available from the jifty subversion repository.

REPORTING BUGS ^

At this incredibly early stage in its life, please report bugs in Jifty to jifty-devel@lists.jifty.org.

FUTURE TUTORIALS ^

Future tutorials include:

syntax highlighting: