Problem with xpath in scrubyt

Ruby
#1

I wrote the below code using scrubyt gem. but it return null value.
But when I run this code using firefox agent it return perfect
results. I do not want to open any agent. Could anyone tell me whats
wrong with the following code.

def self.get_data_from_half_ebay(isbn)
half_ebay_data = Scrubyt::Extractor.define do
fetch “http://search.half.ebay.com/#{isbn}”
henewbooks “//html/body/table[2]/tbody/tr/td/table[4]/tbody/tr/td
[2]/table/tbody/tr/td/table[2]/tbody” do
henb “//tr[@class = ‘tr-border’]” do
henbprice “//span[@class = ‘ItemPrice’]”
henbbuylink “//a[@class = MoreInfo]/@href”
end
end

end
@description = half_ebay_data.to_xml
return @description
end

Regards
Hasinur

#2

On Wed, Jul 15, 2009 at 01:35:10PM +0900, likhon wrote:

henewbooks "//html/body/table[2]/tbody/tr/td/table[4]/tbody/tr/td

end

Firefox adds the “tbody” node. Try your xpath again, but remove
“tbody”.

#3

On Jul 15, 12:32 am, likhon [email protected] wrote:

fetch "http://search.half.ebay.com/#{isbn}"
henewbooks "//html/body/table[2]/tbody/tr/td/table[4]/tbody/tr/td

[2]/table/tbody/tr/td/table[2]/tbody" do
henb “//tr[@class = ‘tr-border’]” do

Positional XPaths like this are fragile. I don’t recommend just taking
the path from Firebug or other DOM inspectors. What happens when
Half.com decides to put a notice in an additional table early in the
page? Your XPath will break.

Instead, think of how a human identifies the item. It’s the table
immediately after the Brand New label, correct? A better XPath would
be:

//table[preceding-sibling::a[1][@name=“itemlist_BRAND_NEW”]]//tr
[@class=“tr-border”]

This does the same thing, but is much less susceptible to unrelated
page changes. If you do a lot of scraping, I recommend really getting
familiar with all that XPath has to offer. DOM inspectors are not
smart enough.

– Mark.