XSLT(not!) with Elegant Dress
You'd swear XSLT is a joke, but it's not. It's cruelty. XSLT is like this: it's good to rid the city of this horrible vermin infestation-- Let's nuke the city. It's an out-of-proportion insanity. It's Turing-complete, and it's XML.
Hmm.
But what it is, is just a set of transformations on fragments of your XML document. The beauty of XSLT (they say), is that XSLT itself is XML, so you can (in principle) use XSLT to transform itself.
Hmm.
Oh I know, how about let's use Ruby?
Transformation Elegant Dress
Honestly, there's not much to it. A Dress
is
just a sequence of transformations you perform on
a DOM tree. Unlike XSLT though, the
transformations are performed directly on the DOM
tree. That is to say, they are destructive.
This is a simple dress,
require 'dress'
doc = "<my><brain></brain></my>"
dress = Dress {
match("brain") do
set("size","pea")
end
}
result = dress.on(doc)
puts result.to_s
# <my><brain "size"="pea"></brain></my>
We can have more matchers,
dress = Dress {
match("brain") do
set("size","pea")
end
match("my") do
each { |e| e.name = "homer"}
end
}
result = dress.on(doc)
puts result.to_s
# <homer><brain "size"="pea"></brain></homer>
Note that match always yield a
Nokogiri::Nodeset
. But sometimes we'd like to
operate on just one node (or the first one we
find). For that there's the at
matcher.
dress = Dress {
at("my") do
me.name = "homer"
end
}
me
is always the object yielded by the matcher
string. For match
it would be a Nodeset, and for
at
, it would be an Element.
We can define helper methods on a Dress. This is one that implements a counter,
dress = Dress {
def count
@count ||= 0
@count += 1
@count
end
match("brain") do
each { |e| e["area"] = count.to_s }
end
}
puts dress.on(Nokogiri.make { my { brain; brain; brain; brain }}).to_s
# <my><brain area="1"></brain><brain area="2"></brain><brain area="3"></brain><brain area="4"></brain></my>
We can combine dresses into lines,
d1 = Dress { ... }
d2 = Dress { ... }
(d1 | d2).on(doc)
We can link lines together,
d3 = Dress { ... }
d4 = Dress { ... }
((d1 | d2) | (d3 | d4)).on(doc)
A dress is a class inheriting from Dress.
class FancyDress < Dress
def helper1
end
def helper2
end
match(...) { ... }
...
end
class PrettyDress < Dress
...
end
Then we can combine these dresses,
(FancyDress | PrettyDress).on(document)
You can of course mix that with dynamic dresses,
(FancyDress | PrettyDress | Dress do ... end).on(doc)
That Wasn't So Hard, Was It?
So Ruby saved us all from XSLT. Minus all the XSLT-inspired buckets of tears, the world is a better place. FTW.
Copyright
Copyright (c) 2009 Howard Yeh. See LICENSE for details.