Catalyst - The Elegant MVC Web Application Framework


Catalyst - The Elegant MVC Web Application Framework


See the the Catalyst::Manual manpage distribution for comprehensive documentation and tutorials.

    # Install Catalyst::Devel for helpers and other development tools
    # use the helper to create a new application MyApp
    # add models, views, controllers
    script/ model MyDatabase DBIC::Schema create=dynamic dbi:SQLite:/path/to/db
    script/ view MyTemplate TT
    script/ controller Search
    # built in testserver -- use -r to restart automatically on changes
    # --help to see all available options
    # command line testing interface
    script/ /yada
    ### in lib/
    use Catalyst qw/-Debug/; # include plugins here as well
    ### In lib/MyApp/Controller/ (autocreated)
    sub foo : Global { # called for /foo, /foo/1, /foo/1/2, etc.
        my ( $self, $c, @args ) = @_; # args are qw/1 2/ for /foo/1/2
        $c->stash->{template} = ''; # set the template
        # lookup something from db -- stash vars are passed to TT
        $c->stash->{data} = 
          $c->model('Database::Foo')->search( { country => $args[0] } );
        if ( $c->req->params->{bar} ) { # access GET or POST parameters
            $c->forward( 'bar' ); # process another action
            # do something else after forward returns            
    # The TT template can use the stash data from the database
    [% WHILE (item = %]
        [% %]
    [% END %]
    # called for /bar/of/soap, /bar/of/soap/10, etc.
    sub bar : Path('/bar/of/soap') { ... }
    # called for all actions, from the top-most controller downwards
    sub auto : Private { 
        my ( $self, $c ) = @_;
        if ( !$c->user_exists ) { # Catalyst::Plugin::Authentication
            $c->res->redirect( '/login' ); # require login
            return 0; # abort request and go immediately to end()
        return 1; # success; carry on to next action
    # called after all actions are finished
    sub end : Private { 
        my ( $self, $c ) = @_;
        if ( scalar @{ $c->error } ) { ... } # handle errors
        return if $c->res->body; # already have a response
        $c->forward( 'MyApp::View::TT' ); # render template
    ### in MyApp/Controller/
    # called for /foo/bar
    sub bar : Local { ... }
    # called for /blargle
    sub blargle : Global { ... }
    # an index action matches /foo, but not /foo/1, etc.
    sub index : Private { ... }
    ### in MyApp/Controller/Foo/
    # called for /foo/bar/baz
    sub baz : Local { ... }
    # first Root auto is called, then Foo auto, then this
    sub auto : Private { ... }
    # powerful regular expression paths are also possible
    sub details : Regex('^product/(\w+)/details$') {
        my ( $self, $c ) = @_;
        # extract the (\w+) from the URI
        my $product = $c->req->captures->[0];

See the Catalyst::Manual::Intro manpage for additional information.


Catalyst is a modern framework for making web applications without the pain usually associated with this process. This document is a reference to the main Catalyst application. If you are a new user, we suggest you start with the Catalyst::Manual::Tutorial manpage or the Catalyst::Manual::Intro manpage.

See the Catalyst::Manual manpage for more documentation.

Catalyst plugins can be loaded by naming them as arguments to the ``use Catalyst'' statement. Omit the Catalyst::Plugin:: prefix from the plugin name, i.e., Catalyst::Plugin::My::Module becomes My::Module.

    use Catalyst qw/My::Module/;

If your plugin starts with a name other than Catalyst::Plugin::, you can fully qualify the name by using a unary plus:

    use Catalyst qw/

Special flags like -Debug and -Engine can also be specified as arguments when Catalyst is loaded:

    use Catalyst qw/-Debug My::Module/;

The position of plugins and flags in the chain is important, because they are loaded in the order in which they appear.

The following flags are supported:


Enables debug output. You can also force this setting from the system environment with CATALYST_DEBUG or <MYAPP>_DEBUG. The environment settings override the application, with <MYAPP>_DEBUG having the highest priority.


Forces Catalyst to use a specific engine. Omit the Catalyst::Engine:: prefix of the engine name, i.e.:

    use Catalyst qw/-Engine=CGI/;


Forces Catalyst to use a specific home directory, e.g.:

    use Catalyst qw[-Home=/usr/mst];

This can also be done in the shell environment by setting either the CATALYST_HOME environment variable or MYAPP_HOME; where MYAPP is replaced with the uppercased name of your application, any ``::'' in the name will be replaced with underscores, e.g. MyApp::Web should use MYAPP_WEB_HOME. If both variables are set, the MYAPP_HOME one will be used.


Specifies log level.


Enables statistics collection and reporting. You can also force this setting from the system environment with CATALYST_STATS or <MYAPP>_STATS. The environment settings override the application, with <MYAPP>_STATS having the highest priority.


   use Catalyst qw/-Stats=1/




Returns a the Catalyst::Action manpage object for the current action, which stringifies to the action name. See the Catalyst::Action manpage.


Returns the namespace of the current action, i.e., the URI prefix corresponding to the controller of the current action. For example:

    # in Controller::Foo::Bar
    $c->namespace; # returns 'foo/bar';



Returns the current the Catalyst::Request manpage object, giving access to information about the current client request (including parameters, cookies, HTTP headers, etc.). See the Catalyst::Request manpage.


$c->forward( $action [, \@arguments ] )

$c->forward( $class, $method, [, \@arguments ] )

Forwards processing to another action, by its private name. If you give a class name but no method, process() is called. You may also optionally pass arguments in an arrayref. The action will receive the arguments in @_ and $c->req->args. Upon returning from the function, $c->req->args will be restored to the previous values.

Any data returned from the action forwarded to, will be returned by the call to forward.

    my $foodata = $c->forward('/foo');
    $c->forward(qw/MyApp::Model::DBIC::Foo do_stuff/);

Note that forward implies an <eval { }> around the call (actually execute does), thus de-fatalizing all 'dies' within the called action. If you want die to propagate you need to do something like:

    die $c->error if $c->error;

Or make sure to always return true values from your actions and write your code like this:

    $c->forward('foo') || return;

$c->detach( $action [, \@arguments ] )

$c->detach( $class, $method, [, \@arguments ] )


The same as forward, but doesn't return to the previous action when processing is finished.

When called with no arguments it escapes the processing chain entirely.



Returns the current the Catalyst::Response manpage object, see there for details.


Returns a hashref to the stash, which may be used to store data and pass it between components during a request. You can also set hash keys by passing arguments. The stash is automatically sent to the view. The stash is cleared at the end of a request; it cannot be used for persistent storage (for this you must use a session; see the Catalyst::Plugin::Session manpage for a complete system integrated with Catalyst).

    $c->stash->{foo} = $bar;
    $c->stash( { moose => 'majestic', qux => 0 } );
    $c->stash( bar => 1, gorch => 2 ); # equivalent to passing a hashref
    # stash is automatically passed to the view for use in a template
    $c->forward( 'MyApp::View::TT' );


$c->error($error, ...)


Returns an arrayref containing error messages. If Catalyst encounters an error while processing a request, it stores the error in $c->error. This method should only be used to store fatal error messages.

    my @error = @{ $c->error };

Add a new error.

    $c->error('Something bad happened');


Contains the return value of the last executed action.


Clear errors. You probably don't want to clear the errors unless you are implementing a custom error screen.

This is equivalent to running




Gets a the Catalyst::Controller manpage instance by name.


If the name is omitted, will return the controller for the dispatched action.


Gets a the Catalyst::Model manpage instance by name.


Any extra arguments are directly passed to ACCEPT_CONTEXT.

If the name is omitted, it will look for - a model object in $c->stash{current_model_instance}, then - a model name in $c->stash->{current_model}, then - a config setting 'default_model', or - check if there is only one model, and return it if that's the case.


Returns the available names which can be passed to $c->controller


Gets a the Catalyst::View manpage instance by name.


Any extra arguments are directly passed to ACCEPT_CONTEXT.

If the name is omitted, it will look for - a view object in $c->stash{current_view_instance}, then - a view name in $c->stash->{current_view}, then - a config setting 'default_view', or - check if there is only one view, and return it if that's the case.


Returns the available names which can be passed to $c->model


Returns the available names which can be passed to $c->view



Gets a component object by name. This method is not recommended, unless you want to get a specific component by full class. $c->controller, $c->model, and $c->view should be used instead.



Returns or takes a hashref containing the application's configuration.

    __PACKAGE__->config( { db => 'dsn:SQLite:foo.db' } );

You can also use a YAML, XML or Config::General config file like myapp.yml in your applications home directory. See the Catalyst::Plugin::ConfigLoader manpage.

    db: dsn:SQLite:foo.db


Returns the logging object instance. Unless it is already set, Catalyst sets this up with a the Catalyst::Log manpage object. To use your own log class, set the logger with the __PACKAGE__->log method prior to calling __PACKAGE__->setup.

 __PACKAGE__->log( MyLogger->new );

And later:

    $c->log->info( 'Now logging with my own logger!' );

Your log class should implement the methods described in the Catalyst::Log manpage.


Overload to enable debug messages (same as -Debug option).

Note that this is a static method, not an accessor and should be overloaded by declaring ``sub debug { 1 }'' in your, not by calling $c->debug(1).


Returns the dispatcher instance. Stringifies to class name. See the Catalyst::Dispatcher manpage.


Returns the engine instance. Stringifies to the class name. See the Catalyst::Engine manpage.



Merges @path with $c->config->{home} and returns a the Path::Class::Dir manpage object.

For example:

    $c->path_to( 'db', 'sqlite.db' );

$c->plugin( $name, $class, @args )

Helper method for plugins. It creates a classdata accessor/mutator and loads and instantiates the given class.

    MyApp->plugin( 'prototype', 'HTML::Prototype' );


Initializes the dispatcher and engine, loads any plugins, and loads the model, view, and controller components. You may also specify an array of plugins to load here, if you choose to not load them in the use Catalyst line.

    MyApp->setup( qw/-Debug/ );

$c->uri_for( $path, @args?, \%query_values? )

Merges path with $c->request->base for absolute URIs and with $c->namespace for relative URIs, then returns a normalized the URI manpage object. If any args are passed, they are added at the end of the path. If the last argument to uri_for is a hash reference, it is assumed to contain GET parameter key/value pairs, which will be appended to the URI in standard fashion.

Instead of $path, you can also optionally pass a $action object which will be resolved to a path using $c->dispatcher->uri_for_action; if the first element of @args is an arrayref it is treated as a list of captures to be passed to uri_for_action.


Returns the Catalyst welcome HTML page.


These methods are not meant to be used by end users.


Returns a hash of components.


Returns or sets the context class.


Returns a hashref containing coderefs and execution counts (needed for deep recursion detection).


Returns the number of actions on the current internal execution stack.


Dispatches a request to actions.


Returns or sets the dispatcher class.


Returns a list of 2-element array references (name, structure) pairs that will be dumped on the error page in debug mode.


Returns or sets the engine class.

$c->execute( $class, $coderef )

Execute a coderef in given class and catch exceptions. Errors are available via $c->error.

$c->_localize_fields( sub { }, \%keys );


Finalizes the request.


Finalizes body.


Finalizes cookies.


Finalizes error.


Finalizes headers.


An alias for finalize_body.


Finalizes the input after reading is complete.


Finalizes uploads. Cleans up any temporary files.

$c->get_action( $action, $namespace )

Gets an action in a given namespace.

$c->get_actions( $action, $namespace )

Gets all actions of a given name in a namespace and all parent namespaces.

$c->handle_request( $class, @arguments )

Called to handle each HTTP request.

$c->prepare( @arguments )

Creates a Catalyst context from an engine-specific request (Apache, CGI, etc.).


Prepares action. See the Catalyst::Dispatcher manpage.


Prepares message body.

$c->prepare_body_chunk( $chunk )

Prepares a chunk of data before sending it to the HTTP::Body manpage.

See the Catalyst::Engine manpage.


Prepares body parameters.


Prepares connection.


Prepares cookies.


Prepares headers.


Prepares parameters.


Prepares path and base.


Prepares query parameters.


Prepares the input for reading.


Prepares the engine request.


Prepares uploads.


Prepares the output for writing.


Returns or sets the request class.


Returns or sets the response class.

$c->read( [$maxlength] )

Reads a chunk of data from the request body. This method is designed to be used in a while loop, reading $maxlength bytes on every call. $maxlength defaults to the size of the request if not specified.

You have to set MyApp->config->{parse_on_demand} to use this directly.

Warning: If you use read(), Catalyst will not process the body, so you will not be able to access POST parameters or file uploads via $c->request. You must handle all body parsing yourself.


Starts the engine.

$c->set_action( $action, $code, $namespace, $attrs )

Sets an action in a given namespace.


Sets up actions for a component.


Sets up components. Specify a setup_components config option to pass additional options directly to the Module::Pluggable manpage. To add additional search paths, specify a key named search_extra as an array reference. Items in the array beginning with :: will have the application class name prepended to them.



Sets up dispatcher.


Sets up engine.


Sets up the home directory.


Sets up log.


Sets up plugins.


Sets up timing statistics class.


Returns a sorted list of the plugins which have either been stated in the import list or which have been added via MyApp->plugin(@args);.

If passed a given plugin name, it will report a boolean value indicating whether or not that plugin is loaded. A fully qualified name is required if the plugin name does not begin with Catalyst::Plugin::.

 if ($c->registered_plugins('Some::Plugin')) {


Returns an arrayref of the internal execution stack (actions that are currently executing).


Returns or sets the stats (timing statistics) class.


Returns 1 when stats collection is enabled. Stats collection is enabled when the -Stats options is set, debug is on or when the <MYAPP>_STATS environment variable is set.

Note that this is a static method, not an accessor and should be overloaded by declaring ``sub use_stats { 1 }'' in your, not by calling $c->use_stats(1).

$c->write( $data )

Writes $data to the output stream. When using this method directly, you will need to manually set the Content-Length header to the length of your output data, if known.


Returns the Catalyst version number. Mostly useful for ``powered by'' messages in template systems.


Catalyst uses internal actions like _DISPATCH, _BEGIN, _AUTO, _ACTION, and _END. These are by default not shown in the private action table, but you can make them visible with a config parameter.

    MyApp->config->{show_internal_actions} = 1;


By default Catalyst is not case sensitive, so MyApp::C::FOO::Bar is mapped to /foo/bar. You can activate case sensitivity with a config parameter.

    MyApp->config->{case_sensitive} = 1;

This causes MyApp::C::Foo::Bar to map to /Foo/Bar.


The request body is usually parsed at the beginning of a request, but if you want to handle input yourself, you can enable on-demand parsing with a config parameter.

    MyApp->config->{parse_on_demand} = 1;

Many production servers operate using the common double-server approach, with a lightweight frontend web server passing requests to a larger backend server. An application running on the backend server must deal with two problems: the remote user always appears to be and the server's hostname will appear to be localhost regardless of the virtual host that the user connected through.

Catalyst will automatically detect this situation when you are running the frontend and backend servers on the same machine. The following changes are made to the request.

    $c->req->address is set to the user's real IP address, as read from 
    the HTTP X-Forwarded-For header.
    The host value for $c->req->base and $c->req->uri is set to the real
    host, as read from the HTTP X-Forwarded-Host header.

Obviously, your web server must support these headers for this to work.

In a more complex server farm environment where you may have your frontend proxy server(s) on different machines, you will need to set a configuration option to tell Catalyst to read the proxied data from the headers.

    MyApp->config->{using_frontend_proxy} = 1;
If you do not wish to use the proxy support at all, you may set:
    MyApp->config->{ignore_frontend_proxy} = 1;


Catalyst has been tested under Apache 2's threading mpm_worker, mpm_winnt, and the standalone forking HTTP server on Windows. We believe the Catalyst core to be thread-safe.

If you plan to operate in a threaded environment, remember that all other modules you are using must also be thread-safe. Some modules, most notably the DBD::SQLite manpage, are not thread-safe.



    Join #catalyst on

Mailing Lists:




the Task::Catalyst manpage - All you need to start with Catalyst

the Catalyst::Manual manpage - The Catalyst Manual

the Catalyst::Component manpage, the Catalyst::Base manpage - Base classes for components

the Catalyst::Engine manpage - Core engine

the Catalyst::Log manpage - Log class.

the Catalyst::Request manpage - Request object

the Catalyst::Response manpage - Response object

the Catalyst::Test manpage - The test suite.


Andy Grundman

Andy Wardley

Andreas Marienborg

Andrew Bramble

Andrew Ford

Andrew Ruthven

Arthur Bergman

Autrijus Tang

Brian Cassidy

Carl Franks

Christian Hansen

Christopher Hicks

Dan Sully

Danijel Milicevic

David Kamholz

David Naughton

Drew Taylor

Gary Ashton Jones

Geoff Richards

Jesse Sheidlower

Jesse Vincent

Jody Belka

Johan Lindstrom

Juan Camacho

Leon Brocard

Marcus Ramberg

Matt S Trout

Robert Sedlacek

Sam Vilain

Sascha Kiefer

Sebastian Willert

Tatsuhiko Miyagawa

Ulf Edvinsson

Yuval Kogman


Sebastian Riedel,


This library is free software, you can redistribute it and/or modify it under the same terms as Perl itself.

 Catalyst - The Elegant MVC Web Application Framework