++ed by:
EGOR ARISTOTLE

2 PAUSE users

Rob N ★
and 1 contributors

NAME

XML::Spice - generating XML has never been so Perly!

SYNOPSIS

    use XML::Spice qw(html head title body h1 p a);

    print
        html(
            head(
                title("my great page"),
            ),
            body(
                h1("my great page"),
                p("this is my great page, made with ", 
                  a("spice", { href => "http://en.wikipedia.org/wiki/Spice/" }),
                ),
            ),
        );

DESCRIPTION

XML::Spice is yet another XML generation module. It tries to take some of the pain out of generating XML by making it more like Perl.

Unless you've got a really good module for producing XML for your particular use (like a module for interfacing with a specific web service), you've probably found that you end up resorting to code like this:

    my $xml = q{<foo><bar><baz /></bar><quux /></foo>};

Of course this works great, and you can't beat it for speed, but it quickly becomes difficult to work with. Your syntax highlighting probably just displays it as a giant string. You can't easily see mismatched brackets or other bugs until your code runs and tries to parse the thing. And, once you start adding attributes and character data into the mix, it rapidly moves towards being impossible to read.

Instead of this, you could use XML::Spice and write the same thing in Perl:

    my $xml = foo(bar(baz()), quux());

You'll can add liberal amounts of whitespace to convey structure without it making your output larger. You get Perl checking to make sure that you haven't left anything out. You can use all the power of Perl to generate and include data without having to pepper your code with interpolated strings or concatenation operators. And you get a guarantee that the XML produced is valid.

BASIC USAGE

If you use (or import) XML::Spice without any arguments, it will export a single function x() into your package. This is the only real function in XML::Spice, and its used to implement everything else.

x() generates a single element, which in turn can contain attributes, character data, sub-elements (via additional calls to x()), and more. The general format for x() is:

    my $xml = x("element", ...);

The first argument is required, and is always the name of the element to generate. So x("foo") produces <foo/>.

Generally though, you'll want to use the more readable named functions to do the work. You get these by providing arguments to XML::Spice when you use it (or call import). For example:

    use XML::Spice qw(foo bar baz);

This will export three functions into your package, foo(), bar() and baz(), and won't import x(). Calling these functions produces the same results as calling x() with the name as the first argument, that is:

    my $xml = foo(...);

produces identical results to:

    my $xml = x("foo", ...);

x() returns an XML::Spice::Chunk object, which when stringified (ie printed or interpolated into a string) produces the XML of its input. Generally you won't care, you'll just stringify it and be done with it. There are however some rather clever things that can be done by having the return value be an object instead of a normal string; see "ADVANCED USAGE" for details.

ARGUMENTS

x() can take zero or more additional arguments. These arguments define what else gets added to the element. What happens depends on what you pass.

attributes

Attributes are added to the element by passing a hash reference, eg:

    img({ src => "hello.jpg" });

produces:

    <img src='hello.jpg' />

If you pass multiple hash references, their contents are combined, with the value from the last hash passed being used in the case of a conflict.

sub-elements

Sub-elements are included in an element by passing the output from another call to x(), eg:

    foo(bar());

produces:

    <foo><bar /></foo>
character data

Character data is added to the element by passing simple strings, eg:

    p("this is my paragraph");

produces:

    <p>this is my paragraph</p>

These arguments can be mixed as much as you like, eg:

    p("Visit my ", a({ href => "http://homepage.com/"}, "homepage"), " for more information.");

produces:

    <p>Visit my <a href='http://homepage.com/'>homepage</a> for more information.</p>

Other things can be passed to x(); those are described in "ADVANCED USAGE".

ADVANCED USAGE

Dynamic tree generation

The most important thing to understand about the XML::Spice::Chunk objects returned by x() is that they do nothing until they are stringified to produce XML output. This makes it possible to pass code references or even other objects to x() and have them dynamically generate data to be included in the produced XML.

If a code reference is passed to x(), it is called when the resultant XML::Spice::Chunk is stringified and its output is included at the position that the code reference was at, eg:

    p("the time is ", sub { scalar localtime });

would produce something like:

    <p>the time is Sat Sep 26 22:32:57 2009</p>

XML::Spice::Chunk will recursively evaluate the result from the code reference until it gets down to basic strings and hash references as described in "BASIC USAGE". This is great for producing lists of things, eg:

    my $list = ul(sub {
        my @results;
        opendir my $dir, "images";
        push @results, li($_) for grep { m/\.png$/ } readdir $dir;
        closedir $dir;
        return @results;
    });

When $list is stringified, the sub will be called and would return a list of XML::Spice::Chunk objects. These in turn will be stringified until eventually only strings are left and output like the following is produced:

    <ul><li>foo.png</li><li>bar.png</li><li>baz.png</li></ul>

Had the sub itself returned a code reference, then that in turn would have been called and its output used.

The code reference is called every time the XML::Spice::Chunk object is stringified. If the computed result will not change, consider caching the result.

To support this, the following things may be passed to x() (and thus returned by code references or objects):

undef

If undef is passed to x(), it is ignored. That is:

    foo("bar", undef, "baz");

is exactly equivalent to:

    foo("bar", "baz");

and produces:

    <foo>barbaz</foo>
array reference

If an array reference is passed to x(), it is flattened. That is:

    foo("bar", [ baz(), "quux" ]);

is exactly equivalent to:

    foo("bar", baz(), "quux");

and produces:

    <foo>bar<baz />quux</foo>

Result cache

A chunk is only evaluated the first time it is stringified. The result is cached and each subsequent stringification will return the cached result. If you wanted to reuse a chunk (eg if it has a coderef in it that does a database lookup), you can call its forget() method to remove the cached result. The next time it is stringified it will be reevaluated from scratch.

PRETTY PRINTING

XML::Spice can produce pretty-printed output. Because the additional whitespace subtly changes the semantics of the generated XML this is only intended as a debugging feature. This also disables the result cache.

To use it, you'll need the XML::Tidy::Tiny module installed. Then to enable it, set (and localise!) $XML::Spice::PRETTY_PRINT to a true value before stringifying a chunk.

TODO

Optimised namespace declarations

If two sub-chunks declare the same namespace, then move the declaration to the parent chunk.

BUGS AND LIMITATIONS

This module guarantees that the XML it produces will be valid and semantically equivalent to the input you give it, but it makes no guarantees and gives no control over things like use of entity encoding vs. CDATA sections, declaration of namespaces and use of prefixes, and so forth. The method used may change between releases, producing different results. If you require exact control over the details of the XML produced, then this module is not for you.

SUPPORT

Bugs / Feature Requests

Please report any bugs or feature requests through the issue tracker at https://github.com/robn/XML-Spice/issues. You will be notified automatically of any progress on your issue.

Source Code

This is open source software. The code repository is available for public review and contribution under the terms of the license.

https://github.com/robn/XML-Spice

  git clone https://github.com/robn/XML-Spice.git

AUTHORS

  • Robert Norris <rob@eatenbyagrue.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2006-2016 by Robert Norris.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.