[catagits/Catalyst-Manual.git] / lib / Catalyst / Manual / Tutorial / 01_Intro.pod

=head1 NAME

Catalyst::Manual::Tutorial::01_Intro - Catalyst Tutorial - Chapter 1: Introduction


=head1 OVERVIEW

This is B<Chapter 1 of 10> for the Catalyst tutorial.

L<Tutorial Overview|Catalyst::Manual::Tutorial>

=over 4

=item 1

B<01_Introduction>

=item 2

L<Catalyst Basics|Catalyst::Manual::Tutorial::02_CatalystBasics>

=item 3

L<More Catalyst Basics|Catalyst::Manual::Tutorial::03_MoreCatalystBasics>

=item 4

L<Basic CRUD|Catalyst::Manual::Tutorial::04_BasicCRUD>

=item 5

L<Authentication|Catalyst::Manual::Tutorial::05_Authentication>

=item 6

L<Authorization|Catalyst::Manual::Tutorial::06_Authorization>

=item 7

L<Debugging|Catalyst::Manual::Tutorial::07_Debugging>

=item 8

L<Testing|Catalyst::Manual::Tutorial::08_Testing>

=item 9

L<Advanced CRUD|Catalyst::Manual::Tutorial::09_AdvancedCRUD>

=item 10

L<Appendices|Catalyst::Manual::Tutorial::10_Appendices>

=back


=head1 DESCRIPTION

This tutorial provides a multi-part introduction to the Catalyst Web
Framework. It seeks to provide a rapid overview of many of its most
commonly used features. The focus is on the real-world best practices
required in the construction of nearly all Catalyst applications.

Although the primary target of the tutorial is users new to the Catalyst
framework, experienced users may wish to review specific sections (for
example, how to use DBIC for their model classes, how to add
authentication and authorization to an existing application, and/or
form management).

The most recent code for the tutorial is included on the Tutorial Virtual
Machine you can download from:

L<http://cattut.shadowcat.co.uk/>

See L</STARTING WITH THE TUTORIAL VIRTUAL MACHINE> below for
instructions getting and using the VM.

Should you wish to download the code directly, you get pull it via the
following command (note: will probably be switching to git soon):

    svn co http://dev.catalyst.perl.org/repos/Catalyst/trunk/examples/Tutorial/ CatalystTutorial

This will download the most recent code for each chapter of the
tutorial into the CatalystTutorial directory on your machine.

These reference implementations are provided so that when you follow
the tutorial, you can use the code to ensure that your system is set up
correctly (which shouldn't be an issue if you use the Tutorial Virtual
Machine), :-) and that you have not inadvertently made any typographic
errors, or accidentally skipped part of the tutorial.

B<NOTE: You can use any Perl-supported OS and environment to run
Catalyst.> It should make little or no difference to Catalyst's
operation, B<but this tutorial has been written using the Debian-based
Tutorial Virtual Machine> that you can download and use to work through
the full tutorial step by step.  B<WE STRONGLY RECOMMEND THAT YOU USE
THE VIRTUAL MACHINE IMAGE TO WORK THROUGH THE TUTORIAL> to avoid issues
that may crop up if you are working with a different configuration.  We
have tested the Tutorial Virtual Machine to make sure all of the
examples work correctly, but it is hard to guarantee this on other
platforms and versions.

If you would prefer to install directly from CPAN and not use the
Tutorial Virtual machine, you can download the example program and all
the necessary dependencies to your local machine by installing the
C<Task::Catalyst::Tutorial> distribution:

     cpan Task::Catalyst::Tutorial

This will also test to make sure the dependencies are working.  If you
have trouble installing these, please ask for help on the #catalyst
IRC channel, or the Catalyst mailing list.

Subjects covered by the tutorial include:

=over 4

=item * 

A simple application that lists and adds books.

=item *

The use of L<DBIx::Class> (DBIC) for the model (including
some of the more advanced techniques you will probably want to use in
your applications).

=item * 

How to write CRUD (Create, Read, Update, and Delete) operations in
Catalyst.

=item *

Authentication ("auth").

=item * 

Role-based authorization ("authz").

=item * 

Attempts to provide an example showing current (5.9) Catalyst
practices.

=item * 

The use of Template Toolkit (TT).

=item * 

Useful techniques for troubleshooting and debugging Catalyst
applications.

=item * 

The use of SQLite as a database (with code also provided for MySQL and
PostgreSQL).  (Note: Because we make use of the DBIx::Class Object
Relational Mapping [ORM] layer, out our application will be database
agnostic and can easily be used by any of the databases supported by
DBIx::Class.)

=item * 

The use of L<HTML::FormFu> or L<HTML::FormHandler>
for automated form processing and validation.

=back

This tutorial makes the learning process its main priority.  For
example, the level of comments in the code found here would likely be
considered excessive in a "normal project."  Because of their contextual
value, this tutorial will generally favor inline comments over a
separate discussion in the text.  It also deliberately tries to
demonstrate multiple approaches to various features (in general, you
should try to be as consistent as possible with your own production
code).

Furthermore, this tutorial tries to minimize the number of controllers,
models, TT templates, and database tables.  Although this does result in
things being a bit contrived at times, the concepts should be applicable
to more complex environments.  More complete and complicated example
applications can be found at
L<http://wiki.catalystframework.org/wiki/resources/catalystexamples> and
in the C<examples> area of the Catalyst Subversion repository at
L<http://dev.catalyst.perl.org/repos/Catalyst/trunk/examples/>.


=head1 STARTING WITH THE TUTORIAL VIRTUAL MACHINE

The steps below briefly outline how you can download the Tutorial
Virtual Machine.  This document uses the term "host machine" to refer to
the physical machine where you will run the virtualization software and
boot up the VM.  The terms "guest machine" or just "VM" refer to the
virtual machine itself -- the thing where you actually do the tutorial
(and that you boot up on the "host machine").
B<Note:> Throughout the tutorial, we will shows the UNIX shell prompt
as "C<$>".  If you are using Tutorial VM, the prompt will really be
"C<root@catalyst:~#>", but we will keep it short (and also use "C<$>" in
lieu of "C<#>", since "C<#>" looks too much like a Perl comment).


=over 4

=item 1 

Download a Tutorial Virtual Machine image from
L<http://cattut.shadowcat.co.uk/>

B<A big thanks to Shadowcat Systems for hosting the virtual machines>
B<(and everything else they do for the Perl community)!>

=item 2

Uncompress the image on the "host machine":

    MAINCOMPUTER:~$ tar zxvf CatalystTutorial.tgz

=item 3

Boot the virtual machine using a tool like VMWare Player
L<http://www.vmware.com/products/player> or VirtualBox
L<http://www.virtualbox.org/>.

=item 4

Once you get a login prompt, enter the username B<root> and a password
for C<catalyst>.  You should now be at a prompt that looks like:

    catalyst login: root
    Password: catalyst
    ...
    root@catalyst:~#

=item 5

Type "C<ifconfig>" to get the IP address assigned to the virtual
machine.  You should get output along the lines of:

    eth0  Link encap:Ethernet  HWaddr 00:01:22:3b:45:69
          inet addr:192.168.0.12  Bcast:192.168.0.255  Mask:255.255.255.0
    ...

You want the IP address on the second line below the C<eth0> interface.
The image it design to automatically use a DHCP-assigned address.


Try to ping this IP address from your "host machine" (main desktop):


    MAINCOMPUTER:~$ ping 192.168.0.12
    PING 192.168.0.12 (192.168.0.12) 56(84) bytes of data.
    64 bytes from 192.168.0.12: icmp_req=1 ttl=255 time=4.97 ms
    64 bytes from 192.168.0.12: icmp_req=2 ttl=255 time=3.43 ms
    ...


B<Note:> The ping above is being originated B<from> your B<host machine>
(main desktop) and going B<to> your guest B<virtual machine>, not the
other way around.

If you are not seeing a valid IP address or it's not responding to pings
(for example, you get error messages along the lines of "Request timed
out", "100% packet loss", or "Destination Host Unreachable"), there
could be a few network-related issues you might need to sort out.  See
the section below L</Sorting Out Virtual Machine Network-Related Issues>
for additional information and troubleshooting advice.

B<Note:> Remember this IP address... you will be using it throughout the
tutorial.


=item 6

B<From your main desktop machine>, open an SSH client and connect to the
IP address found in the previous step.  You should get a login prompt
(accept the SSH key if you get a warning message about that).  Login
with the same username and password as we used in Step 4: B<root> /
B<catalyst>

    catalyst login: root
    Password: catalyst
    ...
    root@catalyst:~#


=item 7

B<Using the SSH session>, change to the sample code directory for
Chapter 3 included with the Tutorial Virtual Machine and start the
Catalyst Development Server:

    $ cd Final/Chapter03/MyApp
    $ perl scripts/myapp_server

=item 8

B<From your main desktop machine> (the "host machine"), open a web
browser and go to B<http://A.B.C.D:3000/>, where C<A.B.C.D> is the IP
address to your virtual machine that you looked up in Step 5.  For
example, if your virtual machine is using the IP address
C<192.168.0.12>, you would put the following URL into your web browser:

    http://192.168.0.12:3000/

Make sure you don't forget the B<:3000> to use port 3000 instead of the
usual port 80 that is used by HTTP by default.

You should get a Catalyst Welcome Screen.  If you do, feel free to jump
right in to L<Chapter 2|Catalyst::Manual::Tutorial::02_CatalystBasics>
of the tutorial.  If you don't go get the Catalyst Welcome Screen, go
back and carefully check each of the steps above.

=item 9

B<Optional:> Also, to reduce download size, the Tutorial VM just
includes a minimal command-line environment.  You are free to use
Debian's very capable C<apt> package manager to install other packages.
You will first want to pull the apt cache files with C<aptitude update>
(or C<apt-get update> if you prefer apt-get).

The VI/VIM editor is already installed on the Tutorial Virtual Machine.
In order to reduce the size of the download, Emacs is not pre-installed.
Since people obviously have very strong opinions about which editor is
best, :-) fortunately it's very easy to install Emacs:

    $ aptitude update
    $ aptitude install emacs

In general, it is expected that people will
boot up the Tutorial VM on their main desktop (the "host machine" using
the terminology above) and then use that main desktop machine to SSH and
web browse into the "guest VM" as they work through the tutorial.  If
you wish to install X Windows (or any other packages), just use the
C<aptitude> (or C<apt-get>) Debian commands.  For example, to install
X Windows with the Gnome desktop manager, you can do:

    $ aptitude update
    $ aptitude install gnome iceweasel

Or, if you prefer KDE:

    $ aptitude update
    $ aptitude install kde iceweasel

You can then start X Windows with:

    $ startx


=back


You may note that the Tutorial Virtual Machine uses L<local::lib> so
that the Perl modules are run from ~/perl5 (in this case, /root/perl5)
vs. the usual location of your "system Perl".  We recommend that you
also consider using this very handy module.  It can greatly ease the
process of maintaining and testing different combinations or Perl
modules across development, staging, and production servers.  (The
"relocatable Perl" feature can also be used to to run both the modules
B<and> Perl itself from your home directory [or any other directory you
chose]).

B<Note>: Please provide feedback on how the Virtual Machine approach for
the tutorial works for you.  If you have suggestions or comments, you
can reach the author through the email address at the bottom of this
page or via an RT ticket at
L<https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.



=head2 Sorting Out Virtual Machine Network-Related Issues

In general, using a virtual machine to work through the tutorial is
*much* easier than trying to do it in other environments, especially if
you are new to Catalyst (or Perl or CPAN or ...).  However, it's
possible that you could run into a few network-related issues.  The good
news is that there is lots of information about the issue available via
search engines on the Internet.  Here is some background information to
get you started.

In Step 5 of the prior section above, we assumed that a "Bridged Mode"
configuration and DHCP will work (it should for most people).  If DHCP
is not working or is not available in your location, most virtual
machine "host" environments let you select between one of several
different types of networking between the "guest" and the "host"
machine.

    1) Bridged
    2) NAT
    3) Local host only

The Tutorial Virtual Machine defaults to "Bridged" -- this should result
in the VM acting like another device on your network that will get a
different DHCP IP address than the host machine.  The advantage of this
approach, is that you can easily SSH and web browse to the guest virtual
machine.  In general, this is the best option if you want to be able to
boot up the VM and then use your SSH client and web browser from your
main machine to connect into the virtual machine.

In some environments, you might have better luck with "NAT" (Network
Address Translation) mode.  With this configuration, the guest VM shares
the same IP address as the host machine.  The downside of this approach
is that special configuration is required if you want to be able to SSH
or web browse to the guest VM.  The NAT option should automatically
allow the VM "outbound connection" (e.g., to the Internet if you want to
install additional Debian packages), but it requires special
configuration if you want to get "inbound connections" that go from some
other machine (including the "host machine") into the VM.  Some virtual
machine host environments let you configure a "static NAT" or "port
forwarding" to reach the guest OS, but others omit this functionality.

"Local host only" mode let's the guest VM and the host machine talk on a
"private subnet" that other devices in your network cannot reach.  This
can work as long as you don't need to go from the VM to the Internet
(for example, to install other Debian packages).

Consult the documentation on your virtual machine host environment for
help configuring the options above.  Here are some links that might
help:

=over 4

=item *

L<http://vmfaq.com/entry/34/>

=item *

L<http://www.vmware.com/support/pubs/player_pubs.html>

=item *

L<http://www.virtualbox.org/manual/ch06.html>

=back




=head1 VERSIONS AND CONVENTIONS USED IN THIS TUTORIAL

This tutorial was built using the following resources. Please note that
you may need to make adjustments for different environments and versions
(note that trailing zeros in version numbers are not significant and may
get dropped with some techniques for viewing them; for example, Catalyst
v5.80020 might show up as 5.8002):

=over 4

=item * 

Debian 6 (Squeeze)

=item * 

Catalyst v5.90002

=item *

Catalyst::Devel v1.34

=item * 

DBIx::Class v0.08195

=item *

Catalyst::Model::DBIC::Schema v0.54

=item *

Template Toolkit v2.22


=item *

HTML::FormFu -- v0.09004

=item * 

B<NOTE:> You can check the versions you have installed with the
following command (note the slash before the space):

    perl -M<_mod_name_>\ 999

or:

    perl -M<_mod_name_> -e 'print "$<_mod_name_>::VERSION\n"'

For example:

    perl -MCatalyst::Devel\ 999

or:

    perl -MCatalyst::Devel -e 'print "$Catalyst::Devel::VERSION\n";'

=item * 

This tutorial will show URLs in the format of C<http://localhost:3000>,
but if you are running your web browser from outside the Tutorial
Virtual Machine, you will want to substitute the IP address of your VM
for the C<localhost> in the URLs (again, you can get the IP address for
eth0 from the C<ifconfig> command).  For example, if your VM has an
IP address of 192.168.0.12, you will want to use a base URL of
C<http://192.168.0.12:3000>.  Note that the development server
defaults to port 3000 (you can change with with the "-p" option on the
command line.

B<Please Note:> Depending on the web browser you are using, you might
need to hit C<Shift+Reload> or C<Ctrl+Reload> to pull a fresh page when
testing your application at various points (see
L<http://en.wikipedia.org/wiki/Wikipedia:Bypass_your_cache> for a
comprehensive list of options for each browser).

Also, the C<-k> B<keepalive option> to the development server can be
necessary with some browsers (B<especially Internet Explorer>).

=back


=head1 DATABASES

This tutorial will primarily focus on SQLite because of its simplicity
of installation and use; however, modifications in the script required
to support MySQL and PostgreSQL will be presented in the Appendix.

B<Note:> One of the advantages of using tools like Catalyst and DBIC is
that applications become much more database independent.  As such, you
will notice that only the C<.sql> files used to initialize the database
change between database systems: most of the code generally remains the
same.


You can jump to the next chapter of the tutorial here:
L<Catalyst Basics|Catalyst::Manual::Tutorial::02_CatalystBasics>


=head1 AUTHOR

Kennedy Clark, C<hkclark@gmail.com>

Feel free to contact the author for any errors or suggestions, but the
best way to report issues is via the CPAN RT Bug system at
L<https://rt.cpan.org/Public/Dist/Display.html?Name=Catalyst-Manual>.

Copyright 2006-2011, Kennedy Clark, under the
Creative Commons Attribution Share-Alike License Version 3.0
(L<http://creativecommons.org/licenses/by-sa/3.0/us/>).