英文:
Having difficulty with CSS selector for multiple possibilities
问题
I'm having difficulty getting a CSS selector to work with Nokogiri. I'm trying
to search for all <tr> nodes that are direct descendants of a
<table> or are direct descendants of a <thead> that is a direct
descendants of a <table>. The following code will clarify the issue:
#!/usr/bin/ruby -w
require 'nokogiri'
puts RUBY_VERSION #=> 2.7.0
puts Nokogiri::VERSION #=> 1.13.6
html = <<~HTML
<html>
<body>
<table>
<thead>
<tr>
<th>city</th>
<th>state</th>
<th>classification</th>
</tr>
</thead>
<tr>
<th>Blacksburg</th>
<td>Virginia</td>
<td>College</td>
</tr>
</table>
</body>
</html>
HTML
doc = Nokogiri::HTML(html)
table = doc.at('table')
puts table.search('> tr').length #=> 1
puts table.search('> thead > tr').length #=> 1
puts table.search('> tr, > thead > tr').length #=> barf
The first two searches work. The third search is what I actually want to do, but
unless I've really forgotten how CSS selectors work (entirely possible) then it
seems to me that third selector should work too. Instead I get this error
message:
Traceback (most recent call last):
12: from ./parse.rb:36:in `<main>'
11: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/xml/searchable.rb:54:in `search'
10: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/xml/searchable.rb:54:in `map'
9: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/xml/searchable.rb:55:in `block in search'
8: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/xml/searchable.rb:245:in `xpath_query_from_css_rule'
7: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/xml/searchable.rb:245:in `map'
6: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/xml/searchable.rb:246:in `block in xpath_query_from_css_rule'
5: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/css.rb:46:in `xpath_for'
4: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/css/parser_extras.rb:78:in `xpath_for'
3: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/css/parser_extras.rb:68:in `parse'
2: from (eval):3:in `do_parse'
1: from (eval):3:in `_racc_do_parse_c'
/var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/css/parser_extras.rb:86:in `on_error': unexpected '>' after ',' (Nokogiri::CSS::SyntaxError)
Ruby version is 2.7.0 and Nokogiri is 1.13.6. Any idea what I'm doing wrong?
英文:
I'm having difficulty getting a CSS selector to work with Nokogiri. I'm trying
to search for all <tr> nodes that are direct descendants of a
<table> or are direct descendants of a <thead> that is a direct
descendants of a <table>. The following code will clarify the issue:
#!/usr/bin/ruby -w
require 'nokogiri'
puts RUBY_VERSION #=> 2.7.0
puts Nokogiri::VERSION #=> 1.13.6
html = <<~'HTML'
<html>
<body>
<table>
<thead>
<tr>
<th>city</th>
<th>state</th>
<th>classification</th>
</tr>
</thead>
<tr>
<th>Blacksburg</th>
<td>Virginia</td>
<td>College</td>
</tr>
</table>
</body>
</html>
HTML
doc = Nokogiri::HTML(html)
table = doc.at('table')
puts table.search('> tr').length #=> 1
puts table.search('> thead > tr').length #=> 1
puts table.search('> tr, > thead > tr').length #=> barf
The first two searches work. The third search is what I actually want to do, but
unless I've really forgotten how CSS selectors work (entirely possible) then it
seems to me that third selector should work too. Instead I get this error
message:
Traceback (most recent call last):
12: from ./parse.rb:36:in `<main>'
11: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/xml/searchable.rb:54:in `search'
10: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/xml/searchable.rb:54:in `map'
9: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/xml/searchable.rb:55:in `block in search'
8: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/xml/searchable.rb:245:in `xpath_query_from_css_rule'
7: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/xml/searchable.rb:245:in `map'
6: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/xml/searchable.rb:246:in `block in xpath_query_from_css_rule'
5: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/css.rb:46:in `xpath_for'
4: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/css/parser_extras.rb:78:in `xpath_for'
3: from /var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/css/parser_extras.rb:68:in `parse'
2: from (eval):3:in `do_parse'
1: from (eval):3:in `_racc_do_parse_c'
/var/lib/gems/2.7.0/gems/nokogiri-1.13.6-x86_64-linux/lib/nokogiri/css/parser_extras.rb:86:in `on_error': unexpected '> ' after ', ' (Nokogiri::CSS::SyntaxError)
Ruby version is 2.7.0 and Nokogiri is 1.13.6. Any idea what I'm doing wrong?
答案1
得分: 0
以下是翻译好的内容：
自然而然，直到我首先向某人提问，我才找到答案。这是一种奇怪的终身模式。无论如何，我将发布答案以供后人参考。答案是要为搜索提供多个参数：
puts table.search('> tr', '> thead > tr').length
英文:
Well naturally I couldn't find the answer myself until I asked someone first. It's a bizarre lifelong pattern. Anyway, I'll post the answer for posterity. The answer is to give multiple arguments to search:
puts table.search('> tr', '> thead > tr').length
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