Editing How to make a Screen perform Actions (section)

===Processing the actions===
The EPrints processor system calls a specified action in a named package (as detailed above)

For each possible action, two functions needed: <code>allow_''action''</code> and <code>action_''action''</code>... where ''action'' is the key given in the buttons hash above.

====The ''allow'' test====
The EPrints processor will always test to see if the user is permitted to perform an action.
A "True" return will permit the action. 
<pre>
sub allow_cancel 
{
   return 1; # everyone can do this "cancel" action
}

sub allow_update
{
    my( $self ) = @_;
    return $self->can_edit; # Only users who have "can_edit" permissions can do this "update" action
}
</pre>

====The actual ''action'' routines====
Assuming that the user is permitted to do the action, then EPrints processor will call the appropriate action routine:
<pre>
sub action_cancel
{
    my( $self ) = @_;

    # Do stuff

}
</pre>

====Getting the parameters====
The parameters are collected from the session:

  my $oname = $self->{session}->param( 'oarj_oname' );

One could be a bit more conservative:

<pre>
  my %params;

  # Have we got any parameters (should be a yes, actions are set in parameters)
  if ($self->{session}->have_parameters)
  {

     # Get a list of all the parameters passed in
     my @param_list = $self->{session}->param;

     # build up a hash of all the parameters
     foreach my $p (@param_list) {
        $params{$p} = $self->{session}->param( $p );
     }
  };
</pre>

.... of course one would assume that, having written the action handler, you know what parameters to expect, and can just ask for them directly!