/ 
HTML-Seamstress-2.0
River stage one • 1 direct dependent • 1 total dependent
/ HTML::Seamstress

NAME

HTML::Seamstress - Perl extension for HTML generation via tree rewriting

SYNOPSIS

HTML "adulterated" with id attributes

<html>
<head>
  <title>Hello World</title>
</head>
<body>
<h1>Hello World</h1>
  <p>Hello, my name is <span id="name">ah, Clem</span>.
  <p>Today's date is <span id="date">Oct 6, 2001</span>.
</body>
</html>

Perl finds nodes in the tree and rewrites them:

use HTML::Seamstress; # HTML::Seamstress isa HTML::TreeBuilder :)
my $tree = HTML::Seamstress->new_from_file($html_file);
$tree->name_handler('bob');
$tree->date_handler(`date`);

sub name_handler {
  my ($tree, $name) = @_;

  my $name_tag = $tree->look_down('id', 'name');
  $name_tag->detach_content; # delete dummy content ("ah, Clem")
  $name_tag->push_content($name);
}

sub date_handler {
  my ($tree, $date) = @_;

  my $name_tag = $tree->look_down('id', 'date');
  $name_tag->detach_content; # delete dummy content ("Oct 6, 2001")
  $name_tag->push_content($date);
}

Or with convenience methods:

use HTML::Seamstress; 
my $tree = HTML::Seamstress->new_from_file($html_file);
$tree->content_handler(name => 'bob');
$tree->content_handler(date => `date`);

DESCRIPTION

From reading HTML::Tree::Scanning, we know that HTML has a tree structure. HTML::Seamstress is a subclass of HTML::TreeBuilder which makes it a little easier to perform common HTML templating operations as tree rewriting.

Text Substitution == Node rewriting

The "SYNOPSIS" gave an example of text substitution. From a tree-writing perspective, text substitution involves an in-place change to the content of a node of an HTML tree.

(Conditional Processing aka if/unless/elsif/else) == Node Deletion

In tree rewriting terms, an if directive is used to decide whether a particular node of the HTML tree is preserved or deleted.

For example, given this Template-style HTML:

[% IF age < 10 %]
      Hello, does your mother know you're 
      using her AOL account?
[% ELSIF age < 18 %]
      Sorry, you're not old enough to enter 
      (and too dumb to lie about your age)
[% ELSE %]
      Welcome
[% END %]

Here is the HTML and Perl for Seamstress:

 <span id=age_handler>
   <span id="under10">
      Hello, does your mother know you're 
      using her AOL account?
   </span>
   <span id="under18">
      Sorry, you're not old enough to enter 
      (and too dumb to lie about your age)
   </span>
   <span id="welcome">
      Welcome
   </span>
 </span>

package HTML::Seamstress
use HTML::Seamstress;
my $tree = HTML::Seamstress->new();
$tree->parse_file($filename);
$tree->age_handler($age);
print $tree->as_HTML;

sub age_handler {
  my ($tree, $age) = @_;
  my $SPAN = $tree->look_down('id', 'age_handler');
  if ($age < 10) {
   $SPAN->look_down('id', $_)->detach for qw(under18 welcome);
  } elsif ($age < 18) {
   $SPAN->look_down('id', $_)->detach for qw(under10 welcome);
 } else {
       $SPAN->look_down('id', $_)->detach for qw(under10 under18);
 }

}

Looping (e.g. able Unrolling) == Child Replication

Sample Model

package Simple::Class;

use Set::Array;

my @name   = qw(bob bill brian babette bobo bix);
my @age    = qw(99  12   44    52      12   43);
my @weight = qw(99  52   80   124     120  230);


sub new {
    my $this = shift;
    bless {}, ref($this) || $this;
}

sub load_data {
    my @data;

    for (0 .. 5) {
	push @data, { 
	    age    => $age[rand $#age] + int rand 20,
	    name   => shift @name,
	    weight => $weight[rand $#weight] + int rand 40
	    }
    }

  Set::Array->new(@data);
}


1;

Sample Usage:

my $data = Simple::Class->load_data;
++$_->{age} for @$data

Inline Code to Unroll a Table

HTML

<html>

  <table id="load_data">

    <tr>  <th>name</th><th>age</th><th>weight</th> </tr>

    <tr id="iterate">

        <td id="name">   NATURE BOY RIC FLAIR  </td>
        <td id="age">    35                    </td>
        <td id="weight"> 220                   </td>

    </tr>

  </table>

</html>

Perl

Program fragment delivered error ``Can't find string terminator "'" anywhere before EOF at lib/HTML/Seamstress.tt line 137, <F> line 47.''

Seamstress API call to Unroll a Table

Program fragment delivered error ``couldnt open file : No such file or directory at ./tt.pl line 18, <F> line 47.''

Looping over Multiple Sample Rows

* HTML

Program fragment delivered error ``syntax error at lib/HTML/Seamstress.tt line 147, near "#line 147 lib/HTML/Seamstress.tt slide_code 'loop/simple-alt.html'"''

* Only one change to last API call.

This:

gi_tr       => 'iterate',

becomes this:

gi_tr       => ['iterate1', 'iterate2']

Whither a Table with No Rows

Use Conditional Processing before Child Replication. In human terms, if (no data) { pop in a no data table } else { pop in the data table }

<span id=no_data>
	<table><tr><td>No Data is Good Data</td></tr></table>
</span>
<span id=load_data>
Program fragment delivered error ``couldnt open file : No such file or directory at ./tt.pl line 18, <F> line 47.''
</span>

EXPORT

None by default.

SEE ALSO

HTML Templating as Tree Rewriting: Part I: "If Statements"

http://perlmonks.org/index.pl?node_id=302606

HTATR II: HTML table generation via DWIM tree rewriting

http://perlmonks.org/index.pl?node_id=303188

Los Angeles Perl Mongers Talk on HTML::Seamstress

http://www.metaperl.com

AUTHOR

Terrence Brannon, <tbone@cpan.org<gt>

COPYRIGHT AND LICENSE

Copyright 2003 by Terrence Brannon.

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