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| − | Documentation is available at http://www.tdom.org/doc-index.html
| + | #REDIRECT [[tDOM]] |
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| − | A very helpful tutorial is available at http://wiki.tcl.tk/8984
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| − | ----
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| − | [[ Dossy]]: [http://www.mail-archive.com/[email protected]/msg06871.html Assigning a prefix to the default namespace when using XPath in tDOM] | |
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| − | I don't know how many folks are using tDOM but I'm sure more and more
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| − | are. I keep stumbling into this problem of trying to access child nodes
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| − | which are in the default namespace but the parent is in a named
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| − | namespace ... and trying to write XPath expressions start to look really
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| − | dog-awful, like:
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| − | $root selectNodes {/*[[local-name()='foo']]/*[[local-name()='bar']]/...}
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| − | So, I sat down for a few minutes and thought about the problem, and
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| − | after some head-scratching, it hit me: name the default namespace. Duh.
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| − | So, here's some sample code:
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| − | ### IMPORTANT: This code lets us get at nodes with a null prefix.
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| − | if {[[$root hasAttribute xmlns]]} {
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| − | $root setAttributeNS "" xmlns:default [[$root getAttribute xmlns]]
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| − | }
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| − | So, now, I can rewrite that XPath expression above:
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| − | $root selectNodes /default:foo/default:bar/...
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| − | Man. Life just couldn't get any better.
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| − | If any of you are wondering why this matters, here's a sample XML doc
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| − | and some sample code illustrating the beauty:
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| − | set xml {
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| − | <aaa:duh xmlns="booboo" xmlns:aaa="blort">
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| − | <foo>
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| − | <bar>some text</bar>
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| − | </foo>
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| − | </aaa:duh>
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| − | }
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| − | $doc [[dom parse $xml]]
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| − | set root [[$doc documentElement]]
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| − | Suppose you want to get the text node inside <bar> with an absolute
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| − | XPath expression. You might think you could write:
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| − | [[$root selectNodes /aaa:duh/foo/bar]] text
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| − | Ah, but XPath *SPANKS* us and tells us we're naughty, that <foo> and
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| − | <bar> have a null prefix and live in the unnamed namespace. That line
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| − | of code returns an empty string, not "some text" as we might have
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| − | expected. So, we tell XPath "well, how about you do me a favor and
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| − | pretend like any node in the unnamed namespace really has a name of my
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| − | choosing ..." by doing this:
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| − | $root setAttributeNS "" xmlns:default [[$root getAttribute xmlns]]
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| − | We're telling the processor to name all nodes in the default namespace
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| − | as though they were in the namespace named "default". N.B.: If your
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| − | XML document really *HAS* a namespace named "default", this code will
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| − | likely CLOBBER it and give you really weird behavior. Change
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| − | "xmlns:default" in the above line to a namespace that won't ever exist
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| − | in your document, then.
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| − | Now that we've done this, lets rewrite that XPath expression and try
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| − | again:
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| − | [[$root selectNodes /aaa:duh/default:foo/default:bar]] text
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| − | Ahh! It returned the string "some text" -- exactly what we wanted.
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| − | Notice the injection of "default:" above before "foo" and "bar" -- since
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| − | we just told the processor that nodes in the unnamed namespace (i.e.,
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| − | <foo> and <bar>) now live in the namespace named "default", in order to
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| − | specify them in an XPath expression, we need to say "default:foo" and
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| − | "default:bar". But this is a hell of a lot easier to read than
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| − | "*[local-name()='foo']" and "*[local-name()='bar']", at least on my
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| − | eyes.
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| − | If this is all old news, feel free to ignore this email. I hadn't seen
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| − | it documented anywhere and I know I've puzzled over this for at least an
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| − | hour or two over the past few months, so maybe this write-up might save
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| − | a few people the same agony.
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