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

Provided by: libtext-micromason-perl_2.23-1_all

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 );

NAME

SYNOPSIS

DESCRIPTION

SEE ALSO