NAME

       Text::MicroMason::Filters - Add Output Filters like "|h" and "|u"

SYNOPSIS

       Instead of using this class directly, pass its name to be mixed in:

           use Text::MicroMason;
           my $mason = Text::MicroMason->new( -Filters );

       Use the standard compile and execute methods to parse and evaluate templates:

         print $mason->compile( text=>$template )->( @%args );
         print $mason->execute( text=>$template, @args );

       Enables filtering of template expressions using syntax similar to that available in HTML::Mason v1:

           <%args> $name </%args>
           Welcome, <% $name |h %>!
           <a href="more.masn?name=<% $name |u %>">Click for More</a>

       You can set default filters, and shut them off using the "n" flag:

           my $mason = Text::MicroMason->new( -Filters, default_filters => 'h' );

           <%args> $name </%args>
           Welcome, <% $name %>!
           <a href="more.masn?name=<% $name |nu %>">Click for More</a>

       You can tell MicroMason to always override default filters instead of combining them:

           my $mason = Text::MicroMason->new( -Filters, default_filters => 'h', default_policy => 'override' );

           <%args> $name </%args>
           Welcome, <% $name %>!
           <a href="more.masn?name=<% $name |u %>">Click for More</a>

       You can define additional filters and stack them:

           my $mason = Text::MicroMason->new( -Filters );
           $mason->filter_functions( myfilter => \&function );
           $mason->filter_functions( uc => sub { return uc( shift ) } );

           <%args> $name </%args>
           Welcome, <% $name |uc,myfilter %>!

DESCRIPTION

       This module enables the filtering of expressions before they are output, using syntax similar to that
       available in HTML::Mason v1.

       Several filter functions come standard with Text::MicroMason. If HTML::Entities available, the "h" filter
       is set up to do HTML encoding. If URI::Escape is available, the "u" filter is set up to provide URI
       escaping. If those modules can not be loaded, no error message is produced but the corresponding filter
       will be unavailable.

       The "p" filter is set up to escape non-ascii characters using Perl backslash notation to make them
       printable. This filter is retained for backwards compatibility, but it is not recommended because it may
       destroy Unicode or other non-ascii byte streams.

       Use "filter_functions()" to define custom filter functions and associate them with filter names.

       Attempting to use an unknown filter name will croak with a message stating "No definition for a filter
       named 'h'".

       When specifying "default_filters()" or using filters in a MicroMason interpolation, there are two ways to
       specify multiple filters. You can only use one of these techinques in a filter specification, but default
       filters and inline filters can be specified differently.

       Up to 5 single character filters can be combined without delimiters:

         <% $name |hu %> Apply the "h" and "u" filters in that order.

       Any number of filter names of any length can be combined with commas and/or spaces:

         <% $name |u,js uc , h %> Apply the "u", "js", "uc", and "h" filters in that order.

       If the "n" filter is specified, all previously specified filters (including default filters) are skipped.

         <% $name |u,h,uc,n,js %> Apply the "js" filter only.
         <% $name |nu %> Skip default filters and apply the "u" filter.

   Public Methods
       filter_functions
           Gets and sets values from the hash mapping filter flags to functions.

           If called with no arguments, returns a hash of all available filter flags and functions:

             %functions = $mason->filter_functions();

           If called with a filter flag returns the associated function, or if provided with a reference to an
           array of flag names returns a list of the functions:

             $function  = $mason->filter_functions( $flag );
             @functions = $mason->filter_functions( \@flags );

           If called with one or more pairs of filter flags and associated functions, adds them to the hash.
           (Any filter that might have existed with the same flag name is overwritten.)

             $mason->filter_functions( $flag => $function, ... );

   Supported Attributes
       default_filters
           Optional comma-separated string of filter flags to be applied to all output expressions unless
           overridden by the "n" flag.

       default_policy
           Optional. Valid values are "combine" and "override"; default is "combine".  This attribute specifies
           what happens when both default_filters and inline filters are provided.

           If "default_policy" is "combine" (the default), then both default filters and inline filters are
           applied (in that order). If "default_policy" is "override", default filters are only applied when no
           inline filters are specified.

           "combine" is the default for backwards compatibility purposes, but new uses of the module probably
           want to use "override" instead.

   Private Methods
       assemble()
           This method goes through the lexed template tokens looking for uses of filter flags, which it then
           rewrites as appropriate method calls before passing the tokens on to the superclass.

       parse_filters
           Parses one or more strings containing any number of filter flags and returns a list of flags to be
           used.

             @flags = $mason->parse_filters( @filter_strings );

           Flags should be separated by commas, except that the commas may be omitted when using a combination
           of single-letter flags. Flags are applied from left to right. Any use of the "n" flag wipes out all
           flags defined to the left of it.

       get_filter_functions
           Accepts filter flags or function references and returns a list of the corresponding functions. Dies
           if an unknown filter flag is used.

             @functions = $mason->get_filter_functions( @flags_or_functions );

       filter
           Applies one or more filters to the provided content string.

             $result = $mason->filter( @flags_or_functions, $content );

SEE ALSO

       For an overview of this templating framework, see Text::MicroMason.

       This is a mixin class intended for use with Text::MicroMason::HTMLMason.

       For distribution, installation, support, copyright and license information, see
       Text::MicroMason::Docs::ReadMe.