5 use HTML::Zoom::ZConfig;
6 use HTML::Zoom::ReadFH;
7 use HTML::Zoom::Transform;
8 use HTML::Zoom::TransformBuilder;
11 our $VERSION = '0.009005';
13 $VERSION = eval $VERSION;
16 my ($class, $args) = @_;
18 $new->{zconfig} = HTML::Zoom::ZConfig->new($args->{zconfig}||{});
22 sub zconfig { shift->_self_or_new->{zconfig} }
25 ref($_[0]) ? $_[0] : $_[0]->new
29 bless({ %{$_[0]}, %{$_[1]} }, ref($_[0]));
33 my $self = shift->_self_or_new;
35 initial_events => shift,
40 my $self = shift->_self_or_new;
41 $self->from_events($self->zconfig->parser->html_to_events($_[0]))
45 my $self = shift->_self_or_new;
47 $self->from_html(do { local (@ARGV, $/) = ($filename); <> });
52 die "No events to build from - forgot to call from_html?"
53 unless $self->{initial_events};
54 my $sutils = $self->zconfig->stream_utils;
55 my $stream = $sutils->stream_from_array(@{$self->{initial_events}});
56 $stream = $_->apply_to_stream($stream) for @{$self->{transforms}||[]};
61 HTML::Zoom::ReadFH->from_zoom(shift);
66 [ $self->zconfig->stream_utils->stream_to_array($self->to_stream) ];
76 my ($self, $code) = @_;
82 my ($self, $predicate, $code) = @_;
94 $self->zconfig->producer->html_from_stream($self->to_stream);
99 ref($self)->new($self)->from_html($self->to_html);
103 my $self = shift->_self_or_new;
104 my ($transform) = @_;
107 @{$self->{transforms}||[]},
114 my $self = shift->_self_or_new;
115 my ($selector, $filter) = @_;
116 $self->with_transform(
117 HTML::Zoom::Transform->new({
118 zconfig => $self->zconfig,
119 selector => $selector,
120 filters => [ $filter ]
126 my $self = shift->_self_or_new;
128 return HTML::Zoom::TransformBuilder->new({
129 zconfig => $self->zconfig,
130 selector => $selector,
135 # There's a bug waiting to happen here: if you do something like
137 # $zoom->select('.foo')
138 # ->remove_attribute(class => 'foo')
140 # ->well_anything_really
142 # the second action won't execute because it doesn't match anymore.
143 # Ideally instead we'd merge the match subs but that's more complex to
144 # implement so I'm deferring it for the moment.
148 die "Can't call ->then without a previous transform"
149 unless $self->{transforms};
150 $self->select($self->{transforms}->[-1]->selector);
154 my ($self, $selector, @args) = @_;
155 my $sel = $self->select($selector);
156 my $meth = our $AUTOLOAD;
158 if(my $cr = $sel->_zconfig->filter_builder->can($meth)) {
159 return $sel->$meth(@args);
161 die "We can't do $meth on ->select('$selector')";
169 HTML::Zoom - selector based streaming template engine
175 my $template = <<HTML;
178 <title>Hello people</title>
181 <h1 id="greeting">Placeholder</h1>
184 <p>Name: <span class="name">Bob</span></p>
185 <p>Age: <span class="age">23</span></p>
187 <hr class="between" />
193 my $output = HTML::Zoom
194 ->from_html($template)
195 ->select('title, #greeting')->replace_content('Hello world & dog!')
196 ->select('#list')->repeat_content(
199 $_->select('.name')->replace_content('Matt')
200 ->select('.age')->replace_content('26')
203 $_->select('.name')->replace_content('Mark')
204 ->select('.age')->replace_content('0x29')
207 $_->select('.name')->replace_content('Epitaph')
208 ->select('.age')->replace_content('<redacted>')
211 { repeat_between => '.between' }
225 <title>Hello world & dog!</title>
228 <h1 id="greeting">Hello world & dog!</h1>
231 <p>Name: <span class="name">Matt</span></p>
232 <p>Age: <span class="age">26</span></p>
234 <hr class="between" />
236 <p>Name: <span class="name">Mark</span></p>
237 <p>Age: <span class="age">0x29</span></p>
239 <hr class="between" />
241 <p>Name: <span class="name">Epitaph</span></p>
242 <p>Age: <span class="age"><redacted></span></p>
252 is($output, $expect, 'Synopsis code works ok');
256 =head1 DANGER WILL ROBINSON
258 This is a 0.9 release. That means that I'm fairly happy the API isn't going
259 to change in surprising and upsetting ways before 1.0 and a real compatibility
260 freeze. But it also means that if it turns out there's a mistake the size of
261 a politician's ego in the API design that I haven't spotted yet there may be
262 a bit of breakage between here and 1.0. Hopefully not though. Appendages
263 crossed and all that.
265 Worse still, the rest of the distribution isn't documented yet. I'm sorry.
266 I suck. But lots of people have been asking me to ship this, docs or no, so
267 having got this class itself at least somewhat documented I figured now was
268 a good time to cut a first real release.
272 HTML::Zoom is a lazy, stream oriented, streaming capable, mostly functional,
273 CSS selector based semantic templating engine for HTML and HTML-like
276 Which is, on the whole, a bit of a mouthful. So let me step back a moment
277 and explain why you care enough to understand what I mean:
281 HTML::Zoom is the cure for JQuery envy. When your javascript guy pushes a
282 piece of data into a document by doing:
284 $('.username').replaceAll(username);
286 In HTML::Zoom one can write
288 $zoom->select('.username')->replace_content($username);
290 which is, I hope, almost as clear, hampered only by the fact that Zoom can't
291 assume a global document and therefore has nothing quite so simple as the
292 $() function to get the initial selection.
294 L<HTML::Zoom::SelectorParser> implements a subset of the JQuery selector
295 specification, and will continue to track that rather than the W3C standards
296 for the forseeable future on grounds of pragmatism. Also on grounds of their
297 spec is written in EN_US rather than EN_W3C, and I read the former much better.
299 I am happy to admit that it's very, very much a subset at the moment - see the
300 L<HTML::Zoom::SelectorParser> POD for what's currently there, and expect more
301 and more to be supported over time as we need it and patch it in.
303 =head2 CLEAN TEMPLATES
305 HTML::Zoom is the cure for messy templates. How many times have you looked at
308 <form action="/somewhere">
309 [% FOREACH field IN fields %]
310 <label for="[% field.id %]">[% field.label %]</label>
311 <input name="[% field.name %]" type="[% field.type %]" value="[% field.value %]" />
315 and despaired of the fact that neither the HTML structure nor the logic are
316 remotely easy to read? Fortunately, with HTML::Zoom we can separate the two
319 <form class="myform" action="/somewhere">
324 $zoom->select('.myform')->repeat_content([
325 map { my $field = $_; sub {
328 ->add_to_attribute( for => $field->{id} )
330 ->replace_content( $field->{label} )
333 ->add_to_attribute( name => $field->{name} )
335 ->add_to_attribute( type => $field->{type} )
337 ->add_to_attribute( value => $field->{value} )
342 This is, admittedly, very much not shorter. However, it makes it extremely
343 clear what's happening and therefore less hassle to maintain. Especially
344 because it allows the designer to fiddle with the HTML without cutting
345 himself on sharp ELSE clauses, and the developer to add available data to
346 the template without getting angle bracket cuts on sensitive parts.
348 Better still, HTML::Zoom knows that it's inserting content into HTML and
349 can escape it for you - the example template should really have been:
351 <form action="/somewhere">
352 [% FOREACH field IN fields %]
353 <label for="[% field.id | html %]">[% field.label | html %]</label>
354 <input name="[% field.name | html %]" type="[% field.type | html %]" value="[% field.value | html %]" />
358 and frankly I'll take slightly more code any day over *that* crawling horror.
360 (addendum: I pick on L<Template Toolkit|Template> here specifically because
361 it's the template system I hate the least - for text templating, I don't
362 honestly think I'll ever like anything except the next version of Template
363 Toolkit better - but HTML isn't text. Zoom knows that. Do you?)
365 =head2 PUTTING THE FUN INTO FUNCTIONAL
367 The principle of HTML::Zoom is to provide a reusable, functional container
368 object that lets you build up a set of transforms to be applied; every method
369 call you make on a zoom object returns a new object, so it's safe to do so
370 on one somebody else gave you without worrying about altering state (with
371 the notable exception of ->next for stream objects, which I'll come to later).
375 my $z2 = $z1->select('.name')->replace_content($name);
377 my $z3 = $z2->select('.title')->replace_content('Ms.');
379 each time produces a new Zoom object. If you want to package up a set of
380 transforms to re-use, HTML::Zoom provides an 'apply' method:
382 my $add_name = sub { $_->select('.name')->replace_content($name) };
384 my $same_as_z2 = $z1->apply($add_name);
386 =head2 LAZINESS IS A VIRTUE
388 HTML::Zoom does its best to defer doing anything until it's absolutely
389 required. The only point at which it descends into state is when you force
390 it to create a stream, directly by:
392 my $stream = $zoom->to_stream;
394 while (my $evt = $stream->next) {
395 # handle zoom event here
400 my $final_html = $zoom->to_html;
402 my $fh = $zoom->to_fh;
404 while (my $chunk = $fh->getline) {
408 Better still, the $fh returned doesn't create its stream until the first
409 call to getline, which means that until you call that and force it to be
410 stateful you can get back to the original stateless Zoom object via:
412 my $zoom = $fh->to_zoom;
414 which is exceedingly handy for filtering L<Plack> PSGI responses, among other
417 Because HTML::Zoom doesn't try and evaluate everything up front, you can
418 generally put things together in whatever order is most appropriate. This
421 my $start = HTML::Zoom->from_html($html);
423 my $zoom = $start->select('div')->replace_content('THIS IS A DIV!');
427 my $start = HTML::Zoom->select('div')->replace_content('THIS IS A DIV!');
429 my $zoom = $start->from_html($html);
431 will produce equivalent final $zoom objects, thus proving that there can be
432 more than one way to do it without one of them being a
433 L<bait and switch|Switch>.
435 =head2 STOCKTON TO DARLINGTON UNDER STREAM POWER
437 HTML::Zoom's execution always happens in terms of streams under the hood
438 - that is, the basic pattern for doing anything is -
440 my $stream = get_stream_from_somewhere
442 while (my ($evt) = $stream->next) {
443 # do something with the event
446 More importantly, all selectors and filters are also built as stream
447 operations, so a selector and filter pair is effectively:
451 my $next_evt = $self->parent_stream->next;
452 if ($self->selector_matches($next_evt)) {
453 return $self->apply_filter_to($next_evt);
459 Internally, things are marginally more complicated than that, but not enough
460 that you as a user should normally need to care.
462 In fact, an HTML::Zoom object is mostly just a container for the relevant
463 information from which to build the final stream that does the real work. A
464 stream built from a Zoom object is a stream of events from parsing the
465 initial HTML, wrapped in a filter stream per selector/filter pair provided
468 The upshot of this is that the application of filters works just as well on
469 streams as on the original Zoom object - in fact, when you run a
470 L</repeat_content> operation your subroutines are applied to the stream for
471 that element of the repeat, rather than constructing a new zoom per repeat
476 $_->select('div')->replace_content('I AM A DIV!');
478 works on both HTML::Zoom objects themselves and HTML::Zoom stream objects and
479 shares sufficient of the implementation that you can generally forget the
480 difference - barring the fact that a stream already has state attached so
481 things like to_fh are no longer available.
483 =head2 POP! GOES THE WEASEL
485 ... and by Weasel, I mean layout.
487 HTML::Zoom's filehandle object supports an additional event key, 'flush',
488 that is transparent to the rest of the system but indicates to the filehandle
489 object to end a getline operation at that point and return the HTML so far.
491 This means that in an environment where streaming output is available, such
492 as a number of the L<Plack> PSGI handlers, you can add the flush key to an
493 event in order to ensure that the HTML generated so far is flushed through
494 to the browser right now. This can be especially useful if you know you're
495 about to call a web service or a potentially slow database query or similar
496 to ensure that at least the header/layout of your page renders now, improving
497 perceived user responsiveness while your application waits around for the
500 This is currently exposed by the 'flush_before' option to the collect filter,
501 which incidentally also underlies the replace and repeat filters, so to
502 indicate we want this behaviour to happen before a query is executed we can
503 write something like:
505 $zoom->select('.item')->repeat(sub {
506 if (my $row = $db_thing->next) {
507 return sub { $_->select('.item-name')->replace_content($row->name) }
511 }, { flush_before => 1 });
513 which should have the desired effect given a sufficiently lazy $db_thing (for
514 example a L<DBIx::Class::ResultSet> object).
516 =head2 A FISTFUL OF OBJECTS
518 At the core of an HTML::Zoom system lurks an L<HTML::Zoom::ZConfig> object,
519 whose purpose is to hang on to the various bits and pieces that things need
520 so that there's a common way of accessing shared functionality.
522 Were I a computer scientist I would probably call this an "Inversion of
523 Control" object - which you'd be welcome to google to learn more about, or
524 you can just imagine a computer scientist being suspended upside down over
525 a pit. Either way works for me, I'm a pure maths grad.
527 The ZConfig object hangs on to one each of the following for you:
531 =item * An HTML parser, normally L<HTML::Zoom::Parser::BuiltIn>
533 =item * An HTML producer (emitter), normally L<HTML::Zoom::Producer::BuiltIn>
535 =item * An object to build event filters, normally L<HTML::Zoom::FilterBuilder>
537 =item * An object to parse CSS selectors, normally L<HTML::Zoom::SelectorParser>
539 =item * An object to build streams, normally L<HTML::Zoom::StreamUtils>
543 In theory you could replace any of these with anything you like, but in
544 practice you're probably best restricting yourself to subclasses, or at
545 least things that manage to look like the original if you squint a bit.
547 If you do something more clever than that, or find yourself overriding things
548 in your ZConfig a lot, please please tell us about it via one of the means
549 mentioned under L</SUPPORT>.
551 =head2 SEMANTIC DIDACTIC
553 Some will argue that overloading CSS selectors to do data stuff is a terrible
554 idea, and possibly even a step towards the "Concrete Javascript" pattern
555 (which I abhor) or Smalltalk's Morphic (which I ignore, except for the part
556 where it keeps reminding me of the late, great Tony Hart's plasticine friend).
558 To which I say, "eh", "meh", and possibly also "feh". If it really upsets
559 you, either use extra classes for this (and remove them afterwards) or
560 use special fake elements or, well, honestly, just use something different.
561 L<Template::Semantic> provides a similar idea to zoom except using XPath
562 and XML::LibXML transforms rather than a lightweight streaming approach -
563 maybe you'd like that better. Or maybe you really did want
564 L<Template Toolkit|Template> after all. It is still damn good at what it does,
567 So far, however, I've found that for new sites the designers I'm working with
568 generally want to produce nice semantic HTML with classes that represent the
569 nature of the data rather than the structure of the layout, so sharing them
570 as a common interface works really well for us.
572 In the absence of any evidence that overloading CSS selectors has killed
573 children or unexpectedly set fire to grandmothers - and given microformats
574 have been around for a while there's been plenty of opportunity for
575 octagenarian combustion - I'd suggest you give it a try and see if you like it.
577 =head2 GET THEE TO A SUMMARY!
581 HTML::Zoom is a lazy, stream oriented, streaming capable, mostly functional,
582 CSS selector based semantic templating engine for HTML and HTML-like
585 But I said that already. Although hopefully by now you have some idea what I
586 meant when I said it. If you didn't have any idea the first time. I mean, I'm
587 not trying to call you stupid or anything. Just saying that maybe it wasn't
588 totally obvious without the explanation. Or something.
592 Maybe we should just move on to the method docs.
598 my $zoom = HTML::Zoom->new;
600 my $zoom = HTML::Zoom->new({ zconfig => $zconfig });
602 Create a new empty Zoom object. You can optionally pass an
603 L<HTML::Zoom::ZConfig> instance if you're trying to override one or more of
604 the default components.
606 This method isn't often used directly since several other methods can also
607 act as constructors, notable L</select> and L</from_html>
611 my $zconfig = $zoom->zconfig;
613 Retrieve the L<HTML::Zoom::ZConfig> instance used by this Zoom object. You
614 shouldn't usually need to call this yourself.
618 my $zoom = HTML::Zoom->from_html($html);
620 my $z2 = $z1->from_html($html);
622 Parses the HTML using the current zconfig's parser object and returns a new
623 zoom instance with that as the source HTML to be transformed.
627 my $zoom = HTML::Zoom->from_file($file);
629 my $z2 = $z1->from_file($file);
631 Convenience method - slurps the contents of $file and calls from_html with it.
635 my $stream = $zoom->to_stream;
637 while (my ($evt) = $stream->next) {
640 Creates a stream, starting with a stream of the events from the HTML supplied
641 via L</from_html> and then wrapping it in turn with each selector+filter pair
642 that have been applied to the zoom object.
646 my $fh = $zoom->to_fh;
648 call_something_expecting_a_filehandle($fh);
650 Returns an L<HTML::Zoom::ReadFH> instance that will create a stream the first
651 time its getline method is called and then return all HTML up to the next
652 event with 'flush' set.
654 You can pass this filehandle to compliant PSGI handlers (and probably most
661 Runs the zoom object's transforms without doing anything with the results.
663 Normally used to get side effects of a zoom run - for example when using
664 L<HTML::Zoom::FilterBuilder/collect> to slurp events for scraping or layout.
668 my $z2 = $z1->apply(sub {
669 $_->select('div')->replace_content('I AM A DIV!') })
672 Sets $_ to the zoom object and then runs the provided code. Basically syntax
673 sugar, the following is entirely equivalent:
676 shift->select('div')->replace_content('I AM A DIV!') })
679 my $z2 = $sub->($z1);
683 my $html = $zoom->to_html;
685 Runs the zoom processing and returns the resulting HTML.
689 my $z2 = $z1->memoize;
691 Creates a new zoom whose source HTML is the results of the original zoom's
692 processing. Effectively syntax sugar for:
694 my $z2 = HTML::Zoom->from_html($z1->to_html);
696 but preserves your L<HTML::Zoom::ZConfig> object.
700 my $zoom = HTML::Zoom->with_filter(
701 'div', $filter_builder->replace_content('I AM A DIV!')
704 my $z2 = $z1->with_filter(
705 'div', $filter_builder->replace_content('I AM A DIV!')
708 Lower level interface than L</select> to adding filters to your zoom object.
710 In normal usage, you probably don't need to call this yourself.
714 my $zoom = HTML::Zoom->select('div')->replace_content('I AM A DIV!');
716 my $z2 = $z1->select('div')->replace_content('I AM A DIV!');
718 Returns an intermediary object of the class L<HTML::Zoom::TransformBuilder>
719 on which methods of your L<HTML::Zoom::FilterBuilder> object can be called.
721 In normal usage you should generally always put the pair of method calls
722 together; the intermediary object isn't designed or expected to stick around.
726 my $z2 = $z1->select('div')->add_to_attribute(class => 'spoon')
728 ->replace_content('I AM A DIV!');
730 Re-runs the previous select to allow you to chain actions together on the
733 =head1 AUTOLOAD METHODS
735 L<HTML::Zoom> AUTOLOADS methods against L</select> so that you can reduce a
736 certain amount of boilerplate typing. This allows you to replace:
738 $z->select('div')->replace_content("Hello World");
742 $z->replace_content(div => "Hello World");
744 Besides saving a few keys per invocations, you may feel this looks neater
745 in your code and increases understanding.
749 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
767 Copyright (c) 2010-2011 the HTML::Zoom L</AUTHOR> and L</CONTRIBUTORS>
772 This library is free software, you can redistribute it and/or modify
773 it under the same terms as Perl itself.