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 $AUTOLOAD;
158 if (ref($selector) eq 'HASH') {
160 $ret = $ret->_do($_, $meth, @{$selector->{$_}}) for keys %$selector;
163 $self->_do($selector, $meth, @args);
168 my ($self, $selector, $meth, @args) = @_;
169 my $sel = $self->select($selector);
170 if( my $cr = $sel->_zconfig->filter_builder->can($meth)) {
171 return $sel->$meth(@args);
173 die "We can't do $meth on ->select('$selector')";
183 HTML::Zoom - selector based streaming template engine
189 my $template = <<HTML;
192 <title>Hello people</title>
195 <h1 id="greeting">Placeholder</h1>
198 <p>Name: <span class="name">Bob</span></p>
199 <p>Age: <span class="age">23</span></p>
201 <hr class="between" />
207 my $output = HTML::Zoom
208 ->from_html($template)
209 ->select('title, #greeting')->replace_content('Hello world & dog!')
210 ->select('#list')->repeat_content(
213 $_->select('.name')->replace_content('Matt')
214 ->select('.age')->replace_content('26')
218 $_->replace_content({'.name' => ['Mark'],'.age' => ['0x29'] })
220 #alternate alternate form
222 $_->replace_content('.name' => 'Epitaph')
223 ->replace_content('.age' => '<redacted>')
226 { repeat_between => '.between' }
240 <title>Hello world & dog!</title>
243 <h1 id="greeting">Hello world & dog!</h1>
246 <p>Name: <span class="name">Matt</span></p>
247 <p>Age: <span class="age">26</span></p>
249 <hr class="between" />
251 <p>Name: <span class="name">Mark</span></p>
252 <p>Age: <span class="age">0x29</span></p>
254 <hr class="between" />
256 <p>Name: <span class="name">Epitaph</span></p>
257 <p>Age: <span class="age"><redacted></span></p>
267 is($output, $expect, 'Synopsis code works ok');
271 =head1 DANGER WILL ROBINSON
273 This is a 0.9 release. That means that I'm fairly happy the API isn't going
274 to change in surprising and upsetting ways before 1.0 and a real compatibility
275 freeze. But it also means that if it turns out there's a mistake the size of
276 a politician's ego in the API design that I haven't spotted yet there may be
277 a bit of breakage between here and 1.0. Hopefully not though. Appendages
278 crossed and all that.
280 Worse still, the rest of the distribution isn't documented yet. I'm sorry.
281 I suck. But lots of people have been asking me to ship this, docs or no, so
282 having got this class itself at least somewhat documented I figured now was
283 a good time to cut a first real release.
287 HTML::Zoom is a lazy, stream oriented, streaming capable, mostly functional,
288 CSS selector based semantic templating engine for HTML and HTML-like
291 Which is, on the whole, a bit of a mouthful. So let me step back a moment
292 and explain why you care enough to understand what I mean:
296 HTML::Zoom is the cure for JQuery envy. When your javascript guy pushes a
297 piece of data into a document by doing:
299 $('.username').replaceAll(username);
301 In HTML::Zoom one can write
303 $zoom->select('.username')->replace_content($username);
305 which is, I hope, almost as clear, hampered only by the fact that Zoom can't
306 assume a global document and therefore has nothing quite so simple as the
307 $() function to get the initial selection.
309 L<HTML::Zoom::SelectorParser> implements a subset of the JQuery selector
310 specification, and will continue to track that rather than the W3C standards
311 for the forseeable future on grounds of pragmatism. Also on grounds of their
312 spec is written in EN_US rather than EN_W3C, and I read the former much better.
314 I am happy to admit that it's very, very much a subset at the moment - see the
315 L<HTML::Zoom::SelectorParser> POD for what's currently there, and expect more
316 and more to be supported over time as we need it and patch it in.
318 =head2 CLEAN TEMPLATES
320 HTML::Zoom is the cure for messy templates. How many times have you looked at
323 <form action="/somewhere">
324 [% FOREACH field IN fields %]
325 <label for="[% field.id %]">[% field.label %]</label>
326 <input name="[% field.name %]" type="[% field.type %]" value="[% field.value %]" />
330 and despaired of the fact that neither the HTML structure nor the logic are
331 remotely easy to read? Fortunately, with HTML::Zoom we can separate the two
334 <form class="myform" action="/somewhere">
339 $zoom->select('.myform')->repeat_content([
340 map { my $field = $_; sub {
343 ->add_to_attribute( for => $field->{id} )
345 ->replace_content( $field->{label} )
348 name => $field->{name},
349 type => $field->{type},
350 value => $field->{value}
355 This is, admittedly, very much not shorter. However, it makes it extremely
356 clear what's happening and therefore less hassle to maintain. Especially
357 because it allows the designer to fiddle with the HTML without cutting
358 himself on sharp ELSE clauses, and the developer to add available data to
359 the template without getting angle bracket cuts on sensitive parts.
361 Better still, HTML::Zoom knows that it's inserting content into HTML and
362 can escape it for you - the example template should really have been:
364 <form action="/somewhere">
365 [% FOREACH field IN fields %]
366 <label for="[% field.id | html %]">[% field.label | html %]</label>
367 <input name="[% field.name | html %]" type="[% field.type | html %]" value="[% field.value | html %]" />
371 and frankly I'll take slightly more code any day over *that* crawling horror.
373 (addendum: I pick on L<Template Toolkit|Template> here specifically because
374 it's the template system I hate the least - for text templating, I don't
375 honestly think I'll ever like anything except the next version of Template
376 Toolkit better - but HTML isn't text. Zoom knows that. Do you?)
378 =head2 PUTTING THE FUN INTO FUNCTIONAL
380 The principle of HTML::Zoom is to provide a reusable, functional container
381 object that lets you build up a set of transforms to be applied; every method
382 call you make on a zoom object returns a new object, so it's safe to do so
383 on one somebody else gave you without worrying about altering state (with
384 the notable exception of ->next for stream objects, which I'll come to later).
388 my $z2 = $z1->select('.name')->replace_content($name);
390 my $z3 = $z2->select('.title')->replace_content('Ms.');
392 each time produces a new Zoom object. If you want to package up a set of
393 transforms to re-use, HTML::Zoom provides an 'apply' method:
395 my $add_name = sub { $_->select('.name')->replace_content($name) };
397 my $same_as_z2 = $z1->apply($add_name);
399 =head2 LAZINESS IS A VIRTUE
401 HTML::Zoom does its best to defer doing anything until it's absolutely
402 required. The only point at which it descends into state is when you force
403 it to create a stream, directly by:
405 my $stream = $zoom->to_stream;
407 while (my $evt = $stream->next) {
408 # handle zoom event here
413 my $final_html = $zoom->to_html;
415 my $fh = $zoom->to_fh;
417 while (my $chunk = $fh->getline) {
421 Better still, the $fh returned doesn't create its stream until the first
422 call to getline, which means that until you call that and force it to be
423 stateful you can get back to the original stateless Zoom object via:
425 my $zoom = $fh->to_zoom;
427 which is exceedingly handy for filtering L<Plack> PSGI responses, among other
430 Because HTML::Zoom doesn't try and evaluate everything up front, you can
431 generally put things together in whatever order is most appropriate. This
434 my $start = HTML::Zoom->from_html($html);
436 my $zoom = $start->select('div')->replace_content('THIS IS A DIV!');
440 my $start = HTML::Zoom->select('div')->replace_content('THIS IS A DIV!');
442 my $zoom = $start->from_html($html);
444 will produce equivalent final $zoom objects, thus proving that there can be
445 more than one way to do it without one of them being a
446 L<bait and switch|Switch>.
448 =head2 STOCKTON TO DARLINGTON UNDER STREAM POWER
450 HTML::Zoom's execution always happens in terms of streams under the hood
451 - that is, the basic pattern for doing anything is -
453 my $stream = get_stream_from_somewhere
455 while (my ($evt) = $stream->next) {
456 # do something with the event
459 More importantly, all selectors and filters are also built as stream
460 operations, so a selector and filter pair is effectively:
464 my $next_evt = $self->parent_stream->next;
465 if ($self->selector_matches($next_evt)) {
466 return $self->apply_filter_to($next_evt);
472 Internally, things are marginally more complicated than that, but not enough
473 that you as a user should normally need to care.
475 In fact, an HTML::Zoom object is mostly just a container for the relevant
476 information from which to build the final stream that does the real work. A
477 stream built from a Zoom object is a stream of events from parsing the
478 initial HTML, wrapped in a filter stream per selector/filter pair provided
481 The upshot of this is that the application of filters works just as well on
482 streams as on the original Zoom object - in fact, when you run a
483 L</repeat_content> operation your subroutines are applied to the stream for
484 that element of the repeat, rather than constructing a new zoom per repeat
489 $_->select('div')->replace_content('I AM A DIV!');
491 works on both HTML::Zoom objects themselves and HTML::Zoom stream objects and
492 shares sufficient of the implementation that you can generally forget the
493 difference - barring the fact that a stream already has state attached so
494 things like to_fh are no longer available.
496 =head2 POP! GOES THE WEASEL
498 ... and by Weasel, I mean layout.
500 HTML::Zoom's filehandle object supports an additional event key, 'flush',
501 that is transparent to the rest of the system but indicates to the filehandle
502 object to end a getline operation at that point and return the HTML so far.
504 This means that in an environment where streaming output is available, such
505 as a number of the L<Plack> PSGI handlers, you can add the flush key to an
506 event in order to ensure that the HTML generated so far is flushed through
507 to the browser right now. This can be especially useful if you know you're
508 about to call a web service or a potentially slow database query or similar
509 to ensure that at least the header/layout of your page renders now, improving
510 perceived user responsiveness while your application waits around for the
513 This is currently exposed by the 'flush_before' option to the collect filter,
514 which incidentally also underlies the replace and repeat filters, so to
515 indicate we want this behaviour to happen before a query is executed we can
516 write something like:
518 $zoom->select('.item')->repeat(sub {
519 if (my $row = $db_thing->next) {
520 return sub { $_->select('.item-name')->replace_content($row->name) }
524 }, { flush_before => 1 });
526 which should have the desired effect given a sufficiently lazy $db_thing (for
527 example a L<DBIx::Class::ResultSet> object).
529 =head2 A FISTFUL OF OBJECTS
531 At the core of an HTML::Zoom system lurks an L<HTML::Zoom::ZConfig> object,
532 whose purpose is to hang on to the various bits and pieces that things need
533 so that there's a common way of accessing shared functionality.
535 Were I a computer scientist I would probably call this an "Inversion of
536 Control" object - which you'd be welcome to google to learn more about, or
537 you can just imagine a computer scientist being suspended upside down over
538 a pit. Either way works for me, I'm a pure maths grad.
540 The ZConfig object hangs on to one each of the following for you:
544 =item * An HTML parser, normally L<HTML::Zoom::Parser::BuiltIn>
546 =item * An HTML producer (emitter), normally L<HTML::Zoom::Producer::BuiltIn>
548 =item * An object to build event filters, normally L<HTML::Zoom::FilterBuilder>
550 =item * An object to parse CSS selectors, normally L<HTML::Zoom::SelectorParser>
552 =item * An object to build streams, normally L<HTML::Zoom::StreamUtils>
556 In theory you could replace any of these with anything you like, but in
557 practice you're probably best restricting yourself to subclasses, or at
558 least things that manage to look like the original if you squint a bit.
560 If you do something more clever than that, or find yourself overriding things
561 in your ZConfig a lot, please please tell us about it via one of the means
562 mentioned under L</SUPPORT>.
564 =head2 SEMANTIC DIDACTIC
566 Some will argue that overloading CSS selectors to do data stuff is a terrible
567 idea, and possibly even a step towards the "Concrete Javascript" pattern
568 (which I abhor) or Smalltalk's Morphic (which I ignore, except for the part
569 where it keeps reminding me of the late, great Tony Hart's plasticine friend).
571 To which I say, "eh", "meh", and possibly also "feh". If it really upsets
572 you, either use extra classes for this (and remove them afterwards) or
573 use special fake elements or, well, honestly, just use something different.
574 L<Template::Semantic> provides a similar idea to zoom except using XPath
575 and XML::LibXML transforms rather than a lightweight streaming approach -
576 maybe you'd like that better. Or maybe you really did want
577 L<Template Toolkit|Template> after all. It is still damn good at what it does,
580 So far, however, I've found that for new sites the designers I'm working with
581 generally want to produce nice semantic HTML with classes that represent the
582 nature of the data rather than the structure of the layout, so sharing them
583 as a common interface works really well for us.
585 In the absence of any evidence that overloading CSS selectors has killed
586 children or unexpectedly set fire to grandmothers - and given microformats
587 have been around for a while there's been plenty of opportunity for
588 octagenarian combustion - I'd suggest you give it a try and see if you like it.
590 =head2 GET THEE TO A SUMMARY!
594 HTML::Zoom is a lazy, stream oriented, streaming capable, mostly functional,
595 CSS selector based semantic templating engine for HTML and HTML-like
598 But I said that already. Although hopefully by now you have some idea what I
599 meant when I said it. If you didn't have any idea the first time. I mean, I'm
600 not trying to call you stupid or anything. Just saying that maybe it wasn't
601 totally obvious without the explanation. Or something.
605 Maybe we should just move on to the method docs.
611 my $zoom = HTML::Zoom->new;
613 my $zoom = HTML::Zoom->new({ zconfig => $zconfig });
615 Create a new empty Zoom object. You can optionally pass an
616 L<HTML::Zoom::ZConfig> instance if you're trying to override one or more of
617 the default components.
619 This method isn't often used directly since several other methods can also
620 act as constructors, notable L</select> and L</from_html>
624 my $zconfig = $zoom->zconfig;
626 Retrieve the L<HTML::Zoom::ZConfig> instance used by this Zoom object. You
627 shouldn't usually need to call this yourself.
631 my $zoom = HTML::Zoom->from_html($html);
633 my $z2 = $z1->from_html($html);
635 Parses the HTML using the current zconfig's parser object and returns a new
636 zoom instance with that as the source HTML to be transformed.
640 my $zoom = HTML::Zoom->from_file($file);
642 my $z2 = $z1->from_file($file);
644 Convenience method - slurps the contents of $file and calls from_html with it.
648 my $stream = $zoom->to_stream;
650 while (my ($evt) = $stream->next) {
653 Creates a stream, starting with a stream of the events from the HTML supplied
654 via L</from_html> and then wrapping it in turn with each selector+filter pair
655 that have been applied to the zoom object.
659 my $fh = $zoom->to_fh;
661 call_something_expecting_a_filehandle($fh);
663 Returns an L<HTML::Zoom::ReadFH> instance that will create a stream the first
664 time its getline method is called and then return all HTML up to the next
665 event with 'flush' set.
667 You can pass this filehandle to compliant PSGI handlers (and probably most
674 Runs the zoom object's transforms without doing anything with the results.
676 Normally used to get side effects of a zoom run - for example when using
677 L<HTML::Zoom::FilterBuilder/collect> to slurp events for scraping or layout.
681 my $z2 = $z1->apply(sub {
682 $_->select('div')->replace_content('I AM A DIV!') })
685 Sets $_ to the zoom object and then runs the provided code. Basically syntax
686 sugar, the following is entirely equivalent:
689 shift->select('div')->replace_content('I AM A DIV!') })
692 my $z2 = $sub->($z1);
696 my $html = $zoom->to_html;
698 Runs the zoom processing and returns the resulting HTML.
702 my $z2 = $z1->memoize;
704 Creates a new zoom whose source HTML is the results of the original zoom's
705 processing. Effectively syntax sugar for:
707 my $z2 = HTML::Zoom->from_html($z1->to_html);
709 but preserves your L<HTML::Zoom::ZConfig> object.
713 my $zoom = HTML::Zoom->with_filter(
714 'div', $filter_builder->replace_content('I AM A DIV!')
717 my $z2 = $z1->with_filter(
718 'div', $filter_builder->replace_content('I AM A DIV!')
721 Lower level interface than L</select> to adding filters to your zoom object.
723 In normal usage, you probably don't need to call this yourself.
727 my $zoom = HTML::Zoom->select('div')->replace_content('I AM A DIV!');
729 my $z2 = $z1->select('div')->replace_content('I AM A DIV!');
731 Returns an intermediary object of the class L<HTML::Zoom::TransformBuilder>
732 on which methods of your L<HTML::Zoom::FilterBuilder> object can be called.
734 In normal usage you should generally always put the pair of method calls
735 together; the intermediary object isn't designed or expected to stick around.
739 my $z2 = $z1->select('div')->add_to_attribute(class => 'spoon')
741 ->replace_content('I AM A DIV!');
743 Re-runs the previous select to allow you to chain actions together on the
746 =head1 AUTOLOAD METHODS
748 L<HTML::Zoom> AUTOLOADS methods against L</select> so that you can reduce a
749 certain amount of boilerplate typing. This allows you to replace:
751 $z->select('div')->replace_content("Hello World");
755 $z->replace_content(div => "Hello World");
757 Besides saving a few keys per invocations, you may feel this looks neater
758 in your code and increases understanding.
762 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
780 Copyright (c) 2010-2011 the HTML::Zoom L</AUTHOR> and L</CONTRIBUTORS>
785 This library is free software, you can redistribute it and/or modify
786 it under the same terms as Perl itself.