NAME

TaglibHelper - module to make it easier to write a taglib

SYNOPSIS

    package My::Taglib;

    use Apache::AxKit::Language::XSP::TaglibHelper;

    @ISA = qw( Apache::AxKit::Language::XSP::TaglibHelper );

    ## Edit $NS to be the namespace URI you want
    $NS = 'http://apache.org/xsp/testtaglib/v1';

    ## Edit @EXPORT_TAGLIB as needed
    @EXPORT_TAGLIB = (
        'func1($arg1)',
        'func2($arg1,$arg2)',
        'func3($arg1,$arg2;$optarg)',
        'func4($arg1,*treearg)',
        'func4($arg1,*treearg):listtag=mylist:itemtag=item',
    );

    use strict;

    sub func1 {
        my ( $arg1 ) = @_ ;
        ...
        return $scalar_or_reference;
    }

...

1;

the functions with the same names as listed in @EXPORT_TAGLIB.

DESCRIPTION

The TaglibHelper module is intended to make it much easier to build a taglib module than had previously existed. When you create a library that uses TaglibHelper, you need only to write ``regular'' functions that take string arguments (optional arguments are supported) and return standard Perl data structures like strings and hashrefs.

FUNCTION SPECIFICATIONS

The @EXPORT_TAGLIB global variable is where you list your exported functions. It is of the format:

  funcname(arguments)[:options]

The <arguments> section contains arguments of the form:

$argument: An argument that is expected to be a plain string

An argument that can take a XML tree in hashref form

@argument

An argument that is expected to be an array of plain strings or an array of hashrefs if the subtag has attributes
@argument: An argument that is expected to be an array of plain strings or an array of hashrefs if the subtag has attributes

These arguments are separated by commas, and optional args are separated from required ones by a semicolon. For example, $field1,$field2;$field3,$field4 has required parameters field1 and field2, and optional parameters field3 and field4.

The options are colon-separated and give extra hints to TaglibHelper in places where the default behavior isn't quite what you want. All options are key/value pairs, formatted as key1=value1:key2=value2, etc. Currently recognized options are:

listtag: For functions that return arrays, use the indicated wrapper tag for the list instead of <funcname>-list
itemtag: For functions that return arrays of strings, use the indicated wrapper tag for the list items instead of <funcname>-item
forcearray: For functions that always return an array, you should generally set this option to ``1''. the reason is that if your array-returning function only returns one value in its array, the result won't be treated as an array otherwise.
conditional: The function's return value will not be printed, and instead will be used to conditionally execute child tags. NOTE that arguments to the function cannot be brought in via child tags, but instead must come in via attributes.
isreally: This function specification is actually an alias for a perl function of a different name. For example, a specification of "person($name):isreally=get_person" allows you to have a tag <ns:person name=``Joe''/> that will resolve to Perl code ``get_person('Joe')''.
as_xml: Set this to true and return a well-balanced chunk of XML, and it will be parsed and added to the output.
array_uses_hash: Set this to true to use the preceding hash key as the prefix to array tag names. In the situation where complex data structures of hashes pointing to arrays are returned, then this makes the xml output more meaningful. Otherwise the default of the itemtag or <funcname>-item is used.

EXAMPLE

if you had these two functions:

  sub hello ($) {
    my ($name) = @_;
    return "Hello, $name!";
  }

  sub get_person ($) {
    my ($name) = @_;
    return { 
        person => { 
        name => $name,
        age => 25,
        height => 200,
        }
    }
  }

...and you called them with this xsp fragment:

  <test:hello>
    <test:name>Joe</test:name>
  </test:hello>

  <test:get-person name="Bob"/>

...you would get this XML result:

  Hello, Joe!
  <person>
    <height>200</height>
    <age>25</age>
  <name>Bob</name></person>

If your function returned deeper result trees, with hashes containing hashrefs or something similar, that would be handled fine. There are some limitations with arrays, however, described in the BUGS AND LIMITATIONS section.

STRUCTURED INPUT EXAMPLE

If you wish to send structured data (i.e. not just a scalar) to a taglib function, use ``*'' instead of ``$'' for a variable. The input to a taglib function specified as ``insert_person($pid,*extra)'' might be:

  <test:insert-person pid="123">
  <test:extra>
      <weight>123</weight>
      <friends>    
       <pid>3</pid>
       <pid>5</pid>
       <pid>13</pid>
      </friends>
  </test:extra>
  </test:insert-person>

The function call would be the same as:

  insert_function("123", { 
    weight => 123, 
    friends => [ 3, 5, 13 ]
    }
  );

The <friends> container holds repeating tags, notice, and TaglibHelper figured out automatically that it needs to use an arrayref instead of hashref for the values. But you'll get unexpected results if you mix repeating tags and nonrepeating ones:

  <test:extra>
    <weight>123</weight>
    <friend>3</friend>
    <friend>5</friend>
    <friend>13</friend>
  </test:extra>

Just wrap your singular repeated tags with a plural-form tag, in this case <friends>.

ARRAY INPUT EXAMPLE

If you wish to send an arbitrary number of values to a taglib function's parameter, use ``@'' instead of ``$'' for the variable in the EXPORT_TAGLIB header array (but still declare it with ``$'' in the function declaration). The parameter will end up turning into an arrayref. For example, you might have a TaglibHelper header:

  listbox($name;$pretty_name,@option,$default,$multiple,$size,$required)

and a Perl declaration:

  sub listbox ($$$$$$$) {
    my ($name, $pretty_name, $options, $default, $multiple, $size, $required) = @_;
        ...
  }

and an XSP file that calls it:

  <test:listbox name="country" pretty_name="Pick a Country" default="" required="1">
    <test:option name="Please choose a country" value=""/>
    <test:option name="United States" value="US"/>
    <test:option name="Canada" value="CA"/>
  </test:listbox>

It would turn into this function call:

  listbox("country", "Pick a Country", [
    { name => "Please choose a country", value => "" },
        { name => "United States", value => "" },
        { name => "Canada", value => "CA" },
  ],  "", undef, undef, 1);

Hopefully the example is clear enough.

BUGS AND LIMITATIONS

Arrays and arrayrefs are generally difficult to work with because the items within the array have no keys other than the index value. As a result, if you want items within an array to be identified correctly, you must currently make all array items point to a hashref that contains the item's key or you must use the optional arguments to give TaglibHelper enough ``hints'' to be able to represent the XML tree the way you want.

AUTHOR

Steve Willer, steve@willer.cc