SVN::Web::action(3p)

NAME
SVN::Web::action - base class for SVN::Web::actions

DESCRIPTION
This is the base class for all SVN::Web actions. It provides a constructor and some useful utility methods that actions may find useful. It also contains documentation for anyone interested in writing new SVN::Web actions.

OVERVIEW
SVN::Web actions are Perl modules loaded by SVN::Web. They are expected to retrieve some information from the Subversion repository, and return that information ready for the user's browser, optionally via formatting by a Template::Toolkit template.

Action names are listed in the SVN::Web configuration file, config.yaml, in the "actions:" clause. Each entry specifies the class that implements the action, and any options that are set globally for that action.

  actions:
    ...
    new_action:
      class: Class::That::Implements::Action
      opts:
        option1: value1
        option2: value2
    ...

Each action is a class that must implement a run() method.

SUBCLASSING
Actions should derive from SVN::Web::action. This gives them a default constructor that generates a hash based object.

  use base 'SVN::Web::action';

METHODS

  run()
The "run" method is where the action carries out its work.

Parameters

The method is passed a single parameter, the standard $self hash ref. This contains numerous useful keys.

$self->{opts}
    The options for this action from config.yaml. Using the example from the OVERVIEW, this would lead to:

      $self->{opts} = { 'option1' => 'value1',
                        'option2' => 'value2',
                      };

$self->{cgi}
    An instance of a CGI object corresponding to the current request. This is normally an object from either the CGI or CGI::Fast modules, although it is possible to specify another class with the "cgi_class" directive in config.yaml.

    You can use this object to retrieve the values of any parameters passed to your action.

    For example, if your action takes a "rev" parameter, indicating the repository revision to work on;

      my $rev = $self->{cgi}->param('rev');

$self->{path}
    The path in the repository that was passed to the action.

$self->{navpaths}
    A reference to an array of path components, one for each directory (and possible final file) in $self->{path}. Equivalent to "[ split('/', $self->{path}) ]"

$self->{config}
    The config hash, as read by YAML from config.yaml. Directives from the config file are second level hash keys. For example, the "actions" configuration directive contains a list of valid actions.

      my @valid_actions = @{ $self->{config}->{actions} };

$self->{reposname}
    The symbolic name of the repository being accessed.

$self->{repos}
    A instance of the SVN::Repos class, corresponding to the repository being accessed. This repository has already been opened.

    For example, to find the youngest (i.e., most recent) revision of the repository;

      my $yr = $self->{repos}->fs()->youngest_rev();

$self->{action}
    The action that has been requested. It's possible for multiple action names to be mapped to a single class in the config file, and this lets you differentiate between them.

$self->{script}
    The URL for the currently running script.

Return value

The return value from run() determines how the data from the action is displayed.

Using a template

If run() wants a template to be displayed containing formatted data from the method then the hash ref should contain two keys.

template
    This is the name of the template to return. By convention the template and the action share the same name.

data
    This is a hash ref. The hash keys become variables of the same name in the template.

The character set and MIME type can also be specified, in the "charset" and "mimetype" keys. If these values are not specified then they default to "UTF-8" and "text/html" respectively.

E.g., for an action named "my_action", using a template called "my_action" that looks like this:

  <p>The youngest interesting revision of [% file %] is [% rev %].</p>

then this code would be appropriate.

  # $rev and $file set earlier in the method
  return { template => 'my_action',
           data     => { rev  => $rev,
                         file => $file,
                       },
         };

Returning data with optional charset and MIME type

If the action does not want to use a template and just wants to return data, but retain control of the character set and MIME type, run() should return a hash ref. This should contain a key called "body", the value of which will be sent directly to the browser.

The character set and MIME type can also be specified, in the "charset" and "mimetype" keys. If these values are not specified then they default to "UTF-8" and "text/html" respectively.

E.g., for an action that generates a PNG image from data in the repository (perhaps using SVN::Churn);

  # $png contains the PNG image, created earlier in the method
  return { mimetype => 'image/png',
           body     => $png
         };

Returning HTML with default charset and MIME type

If the action just wants to return HTML in UTF-8, it can return a single scalar that contains the HTML to be sent to the browser.

  return "<p>hello, world</p>";

UTILITY METHODS
The following methods are intended to share common code among actions.

  recent_interesting_rev($path, $rev)
Given a repository path, and a revision number, returns the most recent interesting revision for the path that is the same as, or older (i.e., smaller) than the revision number.

  get_revs()
Returns a list of 4 items. In order, they are:

Explicit rev
    The value of any CGI "rev" parameter passed to the action ($exp_rev).

Youngest rev
    The repository's youngest revision ($yng_rev) for the current path. This is not necessarily the same as the repositories youngest revision.

Actual rev
    The actual revision ($act_rev) that will be acted on. This is the explicit rev, if it's defined, otherwise it's the youngest rev.

Head
    A boolean value indicating whether or not we can be considered to be at the HEAD of the repository ($at_head).

  format_svn_timestamp()
Given a cstring that represents a Subversion time, format the time using POSIX::strftime() and the current settings of the "timedate_format" and "timezone" configuration directives.

CACHING
If the output from the action can usefully be cached then consider implementing a "cache_key" method.

This method receives the same parameters as the run() method, and must use those parameters to generate a unique key for the content generated by the run() method.

For example, consider the standard "Revision" action. This action only depends on a single parameter -- the repository revision number. So that makes a good cache key.

  sub cache_key {
      my $self = shift;

      return $self->{cgi}->param('rev');
  }

Other actions may have more complicated keys.

ERRORS AND EXCEPTIONS
If your action needs to fail for some reason -- perhaps the parameters passed to it are incorrect, or the user lacks the necessary permissions, then throw an exception.

Exceptions, along with examples, are described in SVN::Web::X.