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Kennedy Clark
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Catalyst::Manual::Tutorial::Intro - Catalyst Tutorial - Part 1: Introduction


This is Part 1 of 10 for the Catalyst tutorial.

Tutorial Overview

  1. Introduction

  2. Catalyst Basics

  3. More Catalyst Basics

  4. Basic CRUD

  5. Authentication

  6. Authorization

  7. Debugging

  8. Testing

  9. Advanced CRUD

  10. Appendices


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, or form management).

You can obtain the code for all the tutorial examples from the catalyst subversion repository by issuing the command:

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

This will download the most recent tarball for each part 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 from the subversion repository to ensure that your system is set up correctly, and that you have not inadvertently made any typographic errors, or accidentally skipped part of the tutorial.

NOTE: You can use any Perl-supported OS and environment to run Catalyst. It should make little or no difference to Catalyst's operation, but this tutorial has been written using the Debian 5 live CD because that represents a quick and easy for most people to try out Catalyst with virtually zero setup time and hassles. Also, the tutorial has been tested to work correctly with the versions of Catalyst and all the supporting modules in Debian 5 (see "VERSIONS AND CONVENTIONS USED IN THIS TUTORIAL" below for the specific versions for some of the key modules), so if you think you might be running into an issue related to versions (for example, a module changed its behavior in a newer version or a bug was introduced), it might be worth giving Debian 5 a try. See the "CATALYST INSTALLATION" section below for more information.

If you're reading this manual online, you can download the example program and all the necessary dependencies to your local machine by installing the Task::Catalyst::Tutorial distribution from CPAN:

     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:

  • A simple application that lists and adds books.

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

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

  • Authentication ("auth").

  • Role-based authorization ("authz").

  • Attempts to provide an example showing current (5.7XXX) Catalyst practices. For example, the use of Catalyst::Action::RenderView, DBIC, Catalyst::Plugin::ConfigLoader with myapp.conf, the use of lib/MyApp/Controller/Root.pm vs. lib/MyApp.pm, etc.

  • The use of Template Toolkit (TT).

  • Useful techniques for troubleshooting and debugging Catalyst applications.

  • The use of SQLite as a database (with code also provided for MySQL and PostgreSQL).

  • The use of HTML::FormFu for automated form processing and validation.

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 in the examples area of the Catalyst Subversion repository at http://dev.catalyst.perl.org/repos/Catalyst/trunk/examples/.


This tutorial was built using the following resources. Please note that you may need to make adjustments for different environments and versions:

  • Debian 5 (Lenny)

  • Catalyst v5.71000

  • Catalyst::Devel v1.08

  • DBIx::Class v0.08012

  • Catalyst Plugins

    The plugins used in this tutorial all have sufficiently stable APIs that you shouldn't need to worry about versions. However, there could be cases where the tutorial is affected by what version of plugins you use. This tutorial has been tested against the following set of plugins:

    • Catalyst::Plugin::Authentication -- v0.10006

    • Catalyst::Plugin::Authorization::Roles -- v0.05

    • Catalyst::Plugin::ConfigLoader -- v0.20

    • Catalyst::Plugin::Session -- v0.19

    • Catalyst::Plugin::Session::State::Cookie -- v0.09

    • Catalyst::Plugin::Session::Store::FastMmap -- v0.05

    • Catalyst::Plugin::StackTrace -- v0.08

    • Catalyst::Plugin::Static::Simple -- v0.20

  • NOTE: You can check the versions you have installed with the following command:

        perl -ME<lt>mod_nameE<gt> -e '"print $E<lt>mod_nameE<gt>::VERSION\n"'

    For example: perl -MCatalyst::Plugin::StackTrace -e 'print "$Catalyst::Plugin::StackTrace::VERSION\n"'

    Since the web browser is being used on the same box where Perl and the Catalyst development server is running, the URL of http://localhost:3000 will be used (the Catalyst development server defaults to port 3000). If you are running Perl on a different box than where your web browser is located (or using a different port number via the -p port_number option to the development server), then you will need to update the URL you use accordingly.

  • Depending on the web browser you are using, you might need to hit Shift+Reload or Ctrl+Reload to pull a fresh page when testing your application at various points (see http://en.wikipedia.org/wiki/Bypass_your_cache for a comprehensive list of options for each browser). Also, the -k keepalive option to the development server can be necessary with some browsers (especially Internet Explorer).


Although Catalyst installation has been a challenge in the past, the good news is that there are a growing number of options to eliminate (or at least dramatically simplify) this concern. Although a compelling strength of Catalyst is that it makes use of many of the modules in the vast repository that is CPAN, this can complicate the installation process if you approach it in the wrong way. Consider the following suggestions on the most common ways to get started with a Catalyst development environment:

  • Debian

    The Debian 5 live CD represents a great way for newcomers to experiment with Catalyst. As a "live CD," you can simple boot from the CD, run a few commands, and in a matter of minutes you should have a fully function environment in which do this tutorial. The tutorial was fully tested to work under Debian 5. Although it SHOULD work under any Catalyst installation method you might choose, it can be hard to guarantee this.

    • Download one of the ISO files from http://cdimage.debian.org/cdimage/release/current-live/i386/iso-cd/. You can pick any one of the live CD variations will work, but you may wish to consider the following points:

      • "debian-live-500-i386-rescue.iso" is probably the best all-around option for most people because it includes many extra tools such as the GCC compiler, therefore saving RAM (every package you need to install when running from live CD consumes memory because RAM disk is being used in lieu of real disk space). When initially booting under this image, you may see some cryptic warning messages having to do with various diagnostic tools it tries to load or enable, but you should be able to safely ignore these.

      • "debian-live-500-i386-standard.iso" is a great option because of its compact size, but you will probably need approximately 1 GB of RAM in the computer where you will run the tutorial. Because the "standard" live CD comes with with a minimal set of tools, we will have to install extra packages (such as the GCC compiler), all of which will require RAM when running from a live CD.

      • The other ISO images include different flavors of X-Windows desktop managers. You can select one of these if you don't mind the larger download size and prefer a graphical environment. Be aware that these disks do not come with the extra tools found on the "rescue" image, so you will need adequate RAM to be able to install them just as you would under the "standard" image. Use one of the "graphical" ISO images if you want a graphical web browser on the same machine as where you will run the tutorial. (If you are using one of the non- graphical images discussed above, you can still use a graphical web browser from another machine and point it to your Catalyst development machine.)

    • Boot off the CD.

    • Select "Live" from the initial boot menu.

    • Once the system has booted to a "user@debian:~$" prompt, enter the following command to add the more current "unstable" package repository:

          sudo vi /etc/apt/sources.list

      Add the following line to the bottom of this file:

          deb http://ftp.us.debian.org/debian/ unstable main

      If you are not familiar with VI, you can move to the bottom of this file and press the "o" key to insert a new line and type the line above. Then press the "Esc" key followed by a colon (":"), the letters "wq" and then the "Enter" key. The rest of the tutorial will assume that you know how to use some editor that is available from the Linux command-line environment.

    • Install Catalyst:

          sudo aptitude update
          sudo aptitude -y install sqlite3 libdbd-sqlite3-perl libcatalyst-perl \
              libcatalyst-modules-perl libconfig-general-perl libsql-translator-perl \
              libdatetime-perl libdatetime-format-mysql-perl libio-all-perl \

      Let it install (normally about a 30-second operaton) and you are done.

      If you are using an image other than the "rescue" ISO, you will also need to run the following command to install additional packages:

          sudo aptitude -y install gcc make libc6-dev

      If you are running from the Live CD, you probably also want to free up some RAM disk space with the following:

          sudo aptitude clean

      NOTE: While the instructions above mention the Live CD because that makes it easy for people new to Linux, you can obviously pick a different Debian ISO image and install it to your hard drive. Although there are many different ways to download and install Debian, the "netinst" ISO image (such as "debian-500-i386-netinst.iso" represents a great option because it keeps your initial download small (but still let's you install anything you want "over the network").

      Here are some tips if you are running from a live CD and are running out of disk space (which really means you are running out of RAM):

      • Always run "aptitude clean" after you install new packages to delete the original .deb files (the files installed by the .deb package will remain available, just the .deb package itself is deleted).

      • If you are installing modules from CPAN, you can free up some space with "rm -rf /root/.cpan/*".

      • If necessary, you can remove the cached package information with the command "rm -f /var/lib/apt/lists/*". You can later pull this information again via the command "aptitude update".

      • You can save a small amount of space by commenting out the lines in /etc/apt/sources.list that reference "deb-src" and "security.debian.org". If you have already done an "aptitude update" with these repositories enabled, you can use the tip in the previous bullet to free the space up (and then do another "aptitude update").

      • Although you can free up space by removing packages you installed since you last booted (check out "aptitude remove _pkg_name"), don't bother trying to remove packages already available at the time of boot. Instead of freeing up space, it will actual consume some space. (The live CD uses these "burn in" packages right from the CD disk vs. first loading them on the virtual RAM disk. However, if you remove them, the system has to update various files, something that does consume some space on the virtual RAM disk.)

  • Ubuntu

    Ubuntu is an extremely popular offshoot of Debian. It provides cutting edge versions of many common tools, application and libraries in an easy-to-run live CD configuration (and because a single download option can be used for both live CD and install-to-disk usage, it keeps your download options nice and simple). As with Debian 5, you should be able to generate a fully function Catalyst environment in a matter of minutes. Here are quick instructions on how to use Ubuntu to prepare for the tutorial:

    • Download the Ubuntu Desktop edition and boot from the CD and/or image file, select your language, and then "Try Ubuntu without any changes to your computer."

    • Open a terminal session (click "Applications" in the upper-left corner, then "Accessories," then "Terminal").

    • Add the 'universe' repositories:

          sudo gedit /etc/apt/sources.list

      And remove the comments from the lines under the comments about the 'universe' repositories.

    • Install Catalyst:

          sudo aptitude update
          sudo aptitude install libdbd-sqlite3-perl libcatalyst-perl libcatalyst-modules-perl libconfig-general-perl

      Accept all of the dependencies. Done.

      If you are running from the Live CD, you probably also want to free up some disk space with the following:

          sudo aptitude clean

      NOTE: While the instructions above mention the live CD because that makes it easy for people new to Linux, you can obviously also use one of the options to install Ubuntu on your drive.

  • Matt Trout's cat-install

    Available at http://www.shadowcatsystems.co.uk/static/cat-install, cat-install can be a fairly painless way to get Catalyst up and running. Just download the script from the link above and type perl cat-install. Depending on the speed of your Internet connection and your computer, it will probably take 30 to 60 minutes to install because it downloads, makes, compiles, and tests every module. But this is an excellent way to automate the installation of all the latest modules used by Catalyst from CPAN.

  • Other Possibilities

For additional information and recommendations on Catalyst installation, please refer to Catalyst::Manual::Installation.


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 Appendix.

Note: One of the advantages of the MVC design patterns is that applications become much more database independent. As such, you will notice that only the .sql files used to initialize the database change between database systems: the Catalyst code generally remains the same.


Each part of the tutorial has complete code available as a tarball in the main Catalyst Subversion repository (see the note at the beginning of each part for the appropriate svn command to use).

NOTE: You can run the test cases for the final code through Part 8 with the following commands:

    sudo cpan Catalyst::Model::DBIC::Schema Time::Warp DBICx::TestDatabase \
        DBIx::Class::DynamicDefault DBIx::Class::TimeStamp
    wget http://dev.catalyst.perl.org/repos/Catalyst/trunk/examples/Tutorial/MyApp_Part8.tgz
    tar zxvf MyApp_Part8.tgz
    cd MyApp
    CATALYST_DEBUG=0 prove --lib lib  t

If you wish to include the HTML::FormFu section in your tests, substitute MyApp_Part9_FormFu.tgz for MyApp_Part8.tgz in the URL above. However, you will also need to run the following additional commands:

    sudo aptitude -y install libhtml-formfu-perl libmoose-perl \
        libregexp-assemble-perl libhtml-formfu-model-dbic-perl
    sudo aptitude clean
    sudo cpan Catalyst::Component::InstancePerContext Catalyst::Controller::HTML::FormFu

You can also fire up the application under the development server that is conveniently built in to Catalyst. Just issue this command from the MyApp directory where you ran the test suite above:


And the application will start. You can try out the application by pulling up http://localhost:3000 in your web browser (as mentioned earlier, change localhost to a different IP address or DNS name if you are running your web browser and your Catalyst development on different boxes). We will obviously see more about how to use the application as we go through the remaining parts of the tutorial, but for now you can log in using the username "test01" and a password of "mypass".


Kennedy Clark, hkclark@gmail.com

Please report any errors, issues or suggestions to the author. The most recent version of the Catalyst Tutorial can be found at http://dev.catalyst.perl.org/repos/Catalyst/Catalyst-Manual/5.70/trunk/lib/Catalyst/Manual/Tutorial/.

Copyright 2006-2008, Kennedy Clark, under Creative Commons License (http://creativecommons.org/licenses/by-sa/3.0/us/).