WWDC2004 Session 417

Transcript

Kind: captions
Language: en
ladies and gentlemen please welcome
software engineer Sarah Wilkin good
morning everyone so I can probably guess
why you're all here which is I got this
quote from this you know the cocoa
mailing list and someone asks well
that's me am I missing something or if
they're actually no xml object for cocoa
well I mean there isn't until today so
what you've had so far is there's the
sax parser and with that you basically
get a bunch of call back as you go
through your XML and that's useful to an
extent where you want to build your own
custom objects but often you just want
that final thing at the end and then
there's CF XML tree which has a lot of
limitations in particular it doesn't
have any sort of namespace handling so
again these are some more quotes from
the developer list people are asking not
just for an XML objects but they're
asking oh well you know I want xpath and
I'm want xquery and xslt and I wanted to
fix my malformed XML and also I you know
really love if it could do
transformations and all sorts of magical
things so that's what I'm going to give
you today we're going to introduce and s
xml
so what is an f xml well it's a set of
five classes in foundation you can
produce xml from scratch you can read in
an xml document or you can start from
HTML convert it into xml find all your
leaf nodes converted you know pull
things out put other things back in and
then just in one line of code you can
apply xquery which is a new w three
standard or XSL see this is all you need
to know if you know a little bit of
cocoa because i'm going to be showing
you quite a bit of code later on and
this in Safari you can go view source
and say hey you know this is the text
element I'm looking for this is the
attribute I'm looking for then you
should be good to go if you're starting
from scratch also you just should know
something about the DTD or the schema so
you can build valid XML so XML it's
everywhere right everywhere you look so
you have XML to straight XML if you go
to the w3 org website you'll see there's
all these different standards and you
can go all over the web and find this
information everywhere and we want you
to use it right then on top of that you
have that file formats so you know kino
actually stores its data as XML it's not
even export it's actually already xml
and illustrator you can escort as SVG
and final cut pro which we're going to
be showing later on then you have t
lists and also services so scraping I
know you all do it and I'm telling you
try to put a stop to that so you know as
I mentioned you can you can do this
custom parsing which is not that great
but otherwise your left scraping these
strings out and you're trying to create
this XML but you know you're going to
end up forgetting an end tag or you're
going to do something a little bit wrong
and then somebody else wants to use your
xml and it's not formed so please stop
use this instead this is NS XML so the
top level we have NF xmlnode which
everything inherits from so what covers
just your basic things attribute
namespace processing a session and text
and these things may or may not have a
name and they'll have an object value
and say where they are in the tree then
you have NF XML document which holds
everything and it will also have a
version and a character encoding then
there's NS XML element where you have
your list of attributes end to your list
of namespaces very important and for
those of you that are into DT DS we have
NSX ml DT D where you have your system
and public ID and it stores a whole
bunch of dte nodes so they'll tell you
what can be valid or not so before I
talk more about this let's show you some
code so it's really easy you just have
your URL and then there's three
different ways you can start creating
your document you can either in it with
contents of URL and it was data or if
you've created a route elephants from
root element from scratch just use that
so I'm going to show how easy it is by
walking all the way over to this demo
machine
so here I have basically the same lines
of code I was just showing and what I'm
doing is I'm getting this from apple.com
/ RSS so as you may know RSS is really
big saying we just announced Safari RSS
and there's all different information
out there available to you so normally
now that Safari RSS is here if we click
on this we get this cool view but we
just want the data so i saved this URL
and this is it here and then I just
alloc init and I'm turning on pretty
printing which is a special option to
make all the indenting go in and then
there's also a root element on the
document so I'm going to go straight
into the debugger and let's be freakin
make sure you can see this all right all
right so let's say I want to print out I
said I has a character encoding right
well utf-8 we have a version okay and
then there's that route which has a name
and it also has attributes
and then faces
a child count and of course there's all
the things you'd expect like child at
index and replace child index all right
let's go back to slides so instead of
doing this please NS XML is for cocoa
lovers use this be happy instead of
doing this custom parts of a socks we
want you to use these risk us objects
instead of doing all the scraping just
use the methods that we have instead of
being difficult it's easy and instead of
it being error-prone and malformed hey
we'll even fix it up for you so this is
you know instead of apples starting from
scratch obviously we're going to use
these great libraries that are already
out there so already live XML tool is in
the system for passer well now we have
lib xslt and tidy then on top of that we
have this you know all of our standards
so if you go to the w3 home page and
look at their specifications well we've
tried to adhere to that pretty well and
as I mentioned we've got this whole
xquery engine in there which I'm going
to show you some xquery later on because
I think it's a really powerful language
for processing XML and previously if
you've developed any sherlock channels
that's what we were using it in we were
using xquery and javascript for channels
and last year we had a sherlock session
there was like hey you know why can't I
use xquery outside of Sherlock well here
you go and then msxml encompasses all of
them so we're going to go into a pretty
long demo but before we get there this
is sort of what I think is what you're
regularly going to do with msxml if you
have some data out there you find it
you're you're pulling a little bit out
of it and then you have some sort of
template and you're pushing in that new
data now i'd like to invite Elena do up
to the stage Elena works on final cut
which can now import an export XML with
final cut
our way to do
we're not ready for the demo messina
with your box blood thank you very much
okay let's just say what a problem is
well it's a typical problem you've got
some sort of person an artist that's
done a really great template and then
you have this database or you have all
the information somewhere and you want
to put it in so you know typical sort of
separation of content and display so in
particular I already sold you the itunes
music store RSS and we're going to use
that again for this demo so we won't
have some sort of template where it has
the song name artist name the rank and
we're going to add in some new
information which is the rank change so
you know so I spiders bugs me that I can
check out well what are the top 10 songs
but are they new today or did they
change from yesterday's number one going
down or is it going up so we're going to
add that in to go to the RSS and then
this is what we want to make is a put
this information into the template so
now we'll go to the demo machine and
this one way we could do this is just
make some simple XML and apply a style
sheet to it and so far I can actually
deal with that so you have this
processing instruction that says this is
my style sheet and you don't even need
to bother writing HTML and it can look
great so we've made this demo for you
that will be available at approximately
6 30 this evening so you can try this
out yourselves and we're just going to
modify it a bit to make it better for
stage so we're just going to build and
run this and here we go so this is XM
elves of style fee it's not HTML so
let's just check out view the source
right so we're going to do something
really similar to this but you know the
web it's good to a certain point can we
go back to 5s but really we want to do
something more exciting we want to make
a video so we're going to do something a
final cut pro and
dead so I just want to give you a
summary of sort of the algorithm we're
going to use so you don't get lost along
the way so this is that what the RSS
looks like I briefly showed it or no I'm
just showing it to you now for the first
time so we have a lots of items and this
is namespace itms so instead of just
being straight regular RSS we've added
in this namespace and it contains a
whole bunch of information attached to
it we have the artist name album the
link and we're going to be using the
link as our sort of unique ID to compare
between the two different versions of
the XML then we're going to use xquery
and extract out the information we want
and at the same time make the XML a lot
simpler to understand so this is at the
point that i left the XML for the sample
code that you'll be looking at so this
is sort of as far as you go and then you
apply to stop soon you're done but here
we're going to go a bit further where
we're actually going to go into final
cut pro and export some xml from
template and then pull all those things
together so our data source as i
mentioned xml is everywhere there's lots
of places to find it I really encourage
you to if you find one data source to
keep looking because the coolest
applications of this is really when you
can bring together lots of different
sources so instead of stopping it
showing the top 10 well maybe I should
go look up information on the artist or
you know find related tracks and also
display that we've already found the
data source so we're not going to bother
showing you that on the demo machine
next we are going to extract the
information so here we are going to use
xquery and of course use ex Corey we
need to know a little bit about ex Corey
so xquery at its basic is it
incorporates X half a next path is quite
straightforward so if you're in your
shell and you can move up and down
directories you can do basic
dot is your context item just like it is
in your directory structure if you want
to go dot slash with a name well that
goes one element down the tree so say I
when dot slash a that would give me all
my links if I went dot / /a that would
give me every single link in the tree
instead of just the children names that
match and dot dot goes up so that's
really straightforward but then we can
add these predicates sentence which
makes it much more powerful because
inside a predicate you can have any
excess or ex Corey function you want and
there's really a lot of them which I'll
show you in a minute or two so you can
do string matching including regular
expressions based on the perl-compatible
regular expression library and will help
match based on what kind of element it
is text or attribute so we'll go back to
the demo machine now and show how easy
this can be so with our our itunes RSS
let's here it is in objective-c we could
say oh give me my first child move down
give me my next child walk through the
tree you try to find this try to find
all the items and the items are could
you just scroll down a bit yes so we
have this whole series of items and if
all you have is items as your children
well that's fine but what if there's a
comment in between well now suddenly you
have to walk through all of the children
just looking for the ones of their items
so xquery lets you know cuts out this
whole stuff so sweet go to the xquery
tab we want to find all the items all we
type is dot slash slash items
and there they are and say we want all
of these song names on those items well
that's itms colon song okay there's all
of our song names and say we want the
song links will we decide on link so
it's really it's that simple I mean
that's a lot easier probably than
whatever you've been doing so if we can
go back to slides now now if we want to
so as mentioning all the functions here
some of them there's around 144 of them
I really encourage you to use ex Corey
when when dealing with XML is a more
fully fledged language so if we want to
do something to each of those items that
we need some sort of iterate or right
and then ex Corey that's called the
flower statement so it's really similar
to an SQL your you know select order by
I think that's going on forever I like
hex queria long so your flower statement
here you have for let order by where and
return and a lot of xquery you'll see
we'll just have a whole bunch of foreign
let statements so for is your iterator
and let is your assignment statement
then you've ordered by and you always
need to have a return which is sometimes
confusing for new people to the language
you can't go let let and return what you
have you have to have the return you
have a really big ex Corey file we also
encourage you to put it in a separate
file which will be doing whereas if you
just have a one-line xpath you should
just write it straight within the code
go back to our demo
so I'm back in NSX in my browser we just
want to show a simple flower statement
before we get into the code here so if
we want to loop over all of the items
you don't say for dollar items dollars
the way of denoting variables next query
and we're going to grab each of the song
name and also get the album title and
then concatenate them together and just
return that and then join the whole
sequence together with returns so if we
run that there we go so in an ex Corey
everything is a sequence even if it's
mine item it's still sequence of one and
you can't nefse quences so in our return
statement if we'd written a return of a
sequence there it would just end up
appending them all together just a
little dot shot that you want to be
watch out for so now we're going to go
straight into the code and go back to I
talked about Steph one but we didn't
show the code because the code is so
similar to what i did in the first demo
so here we are getting our old RSS and
our new RSS and these are sort of
pre-canned versions I saved I think one
of them is from last Friday and one is
on Monday so that will be the two lists
that we're comparing and we go to step
two step two is where we're at actually
applying the xquery so here we're
getting as I mentioned we want to store
it in a separate file because her ex
Corey is quite large which we're going
to go through another minute the NS
bundle we're describing it and then the
next thing you'll notice is this
Constance dictionary so ex Corey as I
mentioned since it's just a one line
function call it can only be really
apply to your current you know that one
object that you're calling it on so we
can say new RSS object
for xquery but we need some way of
getting the old document in there so to
do that we have this constant dictionary
and this key is going to match something
that we declare in the xquery so it's a
way of just passing information in
between four from objective-c and text
query and then our the last line is our
one line that we do to actually apply
the xquery and we're going to get back
this big sequence of items so now I'm
instead of looking at the xquery in
Xcode which has no X query syntax
coloring we're just going to look at a
canned RTF file there it is so X great
comments are these really cute smiley
faces so you're only happy when you're
working on xquery so this is what I saw
him about the first line here this is
where we're bringing in that object that
we declared in our objective c so now
we've got these two documents one is the
context item which is doc and then the
other one is dollar old Doc's then we're
going to loop through so this is like
just a really big version of the small
snippet of X quarter showed you just a
couple of minutes ago so we're getting a
few more attributes than we did before
in addition to the song and song link we
have the artist album and you'll see
here where it goes / text parenthesis
that's matching a text node so you can
also have / attribute / element so it's
really easy to pick out will say I want
all the comments I go fast comment then
we want to find how the old list
comparison in your list so there's that
song link remember which we can use is
the unique ID so we're using this
predicate statement but based on the
song link in that entire array of old
items it's going to find just the one
that matches and of course there's the
chance that doesn't match
longest brand new and we'll deal with
that so then we have this little if
statement you know standard stuff and
we're just building up this string that
says well did the song go up a notch or
down to is it brand new or is unchanged
then the last thing we do if you can see
that far helaina join us move the whole
thing up a bit whole window great up
ok
there we go
so another great thing about xquery is
instead of having to write in line you
know left blah blah blah right and make
sure you match your start and end names
is they have these constructors so I did
this is an element constructor it's
going to build an element with some
attributes and our attributes for giving
special names here because we're going
to use these to match the names that are
in Final Cut Pro and here also anything
above it can be destructive is you can
put any variable you want in there it's
I mean it's not like hard-coded XML
alright so the very end of this hour
loop is done we've created this list
it's a list of items which have these
four attributes which contain
information from the original RSS plus
the rank change and now if we can go
back to floods so now Final Cut Pro we
want to create our template so again
there's lots of different ways of
creating this template if you look at
applications now they can do so much XML
that it's crazy and when you go and
illustrator and you've created this
beautiful graphic and then you can
export it as SVG and programmatically
you know turn it into whatever you want
and like I'm really excited about that
because that's one of the annoying
things for me if you get into this
program and instantly you want to do
something really repetitive especially
in Final Cut Pro and now you can just
export the whole thing use a little bit
of NS xml and xquery and import it back
in and it's all done for you so this is
a couple things we're going to be
looking for in our exported Final Cut
Pro XML a generator item is going to be
our text elements and then the item will
be vegetable text go back to the demo
machine
here we are in final cut pro I know for
most of you like me this was my first
time using final cut pro for this
presentation and it was really fun and
it wasn't that difficult to get
something going and then once I had this
little snippet there well then I could
manipulate it with my mad objective c
programming skills and you don't build
this whole really cool presentation so
here we have our template item and we've
got these for text elements each on
their own track so this is important to
keep in mind because what we're going to
do is duplicate each of these along the
track so we're moving forward in time
and we're going to change this to
actually be a real countdown and then
there needs to be up a little bit of
audio and a little bit of video to spice
it up so we can just export this and
final cut pro it actually exports
everything that you do in it you think
well maybe you know I'm doing this
really cool transition and it's not
going to be able to describe in XML but
you know helaina and others have done
such an excellent job it's all there so
we'll just take a look at what the
exported file looks like so we're giving
it this name that we want to remember
when we're back in our code and we're
just going to search for one of those
strings there it is so if we scroll up a
bit until we hit a generator item so
there's that generator item this is our
generated piece of text and above that
is track so that's the track that the
generated item is on so what we want to
do is take out this template item
because we really don't want something
that says song name and change something
inside it then push it back in multiple
times for each of the four things on
there for different tracks now if we can
go back to slides
okay this is our last step I'm realizing
now you'll be out quite early so we're
going to insert our change coffees so we
had our xml that we created from xquery
and we have this xml that we've exported
from Final Cut Pro then we're going to
put it all together we're going to use
some of these n FX and malfunctions so
on the left-hand side you have all the
sort of attributes of your things and
then on the right-hand side you have
everything dealing with children so I
mean as you can probably guess these
things end up being kvo compliant so
we'll go back to the demo now all right
so oh I forgot of stuff step 3 okay
after we exported the Final Cut Pro XML
and I showed you where that generator
item and the track are now we want to
find those so we're importing the
template then we have our array with the
four keys and remember we named in Final
Cut Pro we named our text with the same
names with the attribute names that we
export from xquery so we're just going
to loop through each of those four
things and we want to build one array
it's the generator items and another
array of the tracks because ultimately
the generator items are going to
disappear from the original and we want
to assert things into the tracks
there's that little bit of xpath there
what tries to explain so we want to find
within that big exported file just that
one particular generator item right and
to do that we go you look for all the
generator items then we have this
predicate we're inside there we look for
a text element that matches based on the
name of wherever we are inside our array
then we add the generator object and
also its parent to text notes and track
notes the last thing we do in the loop
is detached it which is you know
obviously another msxml question which
just takes something right out of the
tree basically setting it's apparent to
nail and deleting it from the from the
parent okay step 4 slow last up so you
see lengths there this is so we can move
ahead of time we're going around 30
frames with back down we want each thing
to play for two seconds then we get that
first item so we've got these ten items
from ex Corey remember so that's current
then we're looping through our for
special keys and the first thing we do
flick it is the actual generator item
because that's the lonely one with serve
our new text in then we come up with our
replacement string which is the
attribute with the same name matching
one of those keys and now we find just
the text node so we do a little bit more
xpath just to find the text no because
remember we don't want to replace the
whole text of the generator item we just
want our place that the text and where
it belongs so we set the string value
and then that dot saw start and dot
slash ends those are certain end times
we want to make sure that we have to
move forward in time and don't end up
with our ten clips on top of each other
then we add our child
and release it and we're done so I mean
that's that's really all there is to it
so let's go back let's let's run this so
it see the variance that we just write
it back to a file
okay and then we can go back and find
without pro and import this and it
should have our 10 bits from the RSS in
Final Cut moving along in time
there they are so we can see we've we've
added that additional information of you
know whether it's unchanged or moved up
and down so let's I just switch to our
app reek and rendered version of this
and play it back if your looks like
[Music]
yeah made a whole movie with XML at
what's the name of the band again be
expendable from Santa Cruz they're
really nice they lent us this footage
and their music so we're not stepping on
anyone's feet now let's say I go back to
flood so in addition to everything i
just showed you i just want to show you
a few more header highlights so in
addition to exporting xml we're also can
export XHTML or HTML and at this point i
will encourage you to read the release
notes because there's some things that
aren't quite finished and there's a
couple knowing bugs that we don't want
you are hitting upon but there's
generally workarounds that are known you
can also set string value resolving
entities so this is something that i
mean i really like because it means in
your DTD you can just say hey this
string should resolve to this other
string and then pass it in with entity
and have it resolve for you so you don't
have to parse through your string and
replace it later on i showed you objects
for ex Corey there's also object by
applying excess ltd which is you know
another great language / technology it's
sort of in theory similar to ex Corey
that I think X squares a bit more
powerful an xslt you can also do some
other things like you can export RTF or
you can export PDF depending on how you
write your xslt so that's why I'm its
object by applying xslt instead of
document because you can get either
enough data back or you can get an NS
XML document then there's also resolved
namespace for name as I mentioned we put
a lot of work into having the namespaces
just work so when you add something and
we'll actually go and find the
namespaces associated with which means
you can say hey what's the name space
for barca land baths and
we'll say oh sh t TR com then we have
fidelity which for those of you that are
using straight lib XML to right now is
something I know you're not getting
because it was quite a bit of work to
get this in there so what I mean by
fidelity is just that your input you
know you probably want it to look like
your output so if you've got white space
in between your elements you might want
to keep that if you use single quotes or
double quotes on your attributes you
know you might have some reason that you
want to keep those around and prefixes
entities so all of this stuff also keep
in mind though that this will be a
performance hit I've tested this if you
turn on all of these options you'll get
a boat of fifty percent performance it
on per se so just use the ones that you
really need and bindings so you briefly
saw the little NS XML application and
since we have a minute i'm just going to
show you a little bit more of it if we
go to the demo machine so there's a
whole tab here which i didn't show you
which is where the whole TV oq vc comes
in so we have our source here and
there's this editor tab and you can just
move down the tree those up the tree and
edit things here you can see there's
some name station attributes and find
the information about the document and
it really didn't take me long to put
this together it was an exercise and
seeing if her bindings works and they do
I mean it's great it's basically you
know you can build a whole XML editor
really quickly and it also wouldn't take
much effort if you guys went to the
what's new and cocoa talk they said that
there's new bindings for trees you
should be able to just put an extra
class in there that steps to this and be
able to do an outline view editor you
know in a day and let's go back to
slides
so
that's it I want to see what you can do
we're giving you all of the stuff it you
know there's that option NS XML document
tidy HTML which takes your HTML and
converts it into validate XML you can
also tidy up XML and that you may have
guessed we're using natural HTML tidy
library if you've heard of it salsa
vailable deviated there's are five
classes and ass XML document node
element DTD and dte node and one of the
first ex Corey engines as i mentioned
xquery is now its final call happened in
February so it's really getting to be a
stabilized language we don't expect
major things happening like they have
been the past couple years and please
file bugs I know of a bunch but you're
probably going to find a bunch more so I
can't find out about them unless you
file them so get on your bug reporter
follow them in also enhancements we know
that we haven't covered everything they
are interested in I'm especially
interested in hearing what people want
more from the DTD stuff and validation a
Matthew formica is our cocoa evangelist
he should be your first sort of email
contact and then there's jungle NZ who
you probably met at the H hi talk we
have a bunch of great documentation that
Terry put together who you'll see in QA
in addition to the regular foundation
web page in a way you'll see the new
classes there's also this whole you know
prose based hey what's msxml and it goes
into how xml browser was put together
how the bindings go together little code
snippets and there's the two things I
showed you the top 40 that first version
with CSS and XML browser which I just
showed you a little bit more of the full
code is available for that it will be up
on the server around six-thirty today
and w3 is really the definitive resource
for all of this because xquery is a
pretty new line
good you should really go to them for
but more tutorials or coming up I'd like
to thank you very much