Help with regular expression

Rails
1

Someone helped me earlier today with a method to remove the “pre” tag
block and replace it with ‘’. This is because when I’m showing snippets
of a post, I don’t want a piece of code to be in the snippet. Anyway,
here’s what I’m doing:

works perfect (only for pre)

def strip_pre_block
text.gsub(/

[^<]*</pre>/,’’)

end

Now, I want to do the same with blockquote.  How can I combine the two?

Something like this:


doesn’t work at all (for either one)


def strip_pre_and_quote_blocks

text.gsub(/(^
[^<]</pre>$|^
.
</blockquote>$)/,’’)

end

When I try that, it doesn’t replace either one of the “pre” or

“blockquote” blocks with ‘’, but the first method works perfect for the

“pre” block only.  I can’t even get the blockquote one to work by

itself.


Can someone help out with this???  Thanks in advance…
2

I should note, the format of my blockquotes look like this:

Quote goes here

I may have been ignoring the “p” tags so it didn’t work.

Still can’t get it. Any help is greatly appreciated.

3

ryan wrote:

doesn’t work at all (for either one)

def strip_pre_and_quote_blocks
text.gsub(/(^

[^<]</pre>$|^

.</blockquote>$)/,‘’)

end




Here are some general suggestions. Write a test case for this regexp,

have

it print out a result, and run it over and over again as you

incrementally

add elements. I note this because you appear to have leapt directly from

a

simple to a complex regexp without incrementally examining the reaction

to

each individual symbol. Get used to writing test cases as experiments,

and

frequently running them (with one keystroke preferrably).


Next, put the ^ and $ outside the (), on principle.


Next, try (
|
).


Next, [^<]* is always tempting, but you can get less greedy IIRC with

.*?.

That will look-ahead a little more.


Next, post this to a Ruby or Regex newsgroup, because it’s not about

Rails.


Next, treat your HTML as XHTML and parse it with REXML. You can use

XPath to

reach in and nab each pre, and change its tag or contents to whatever

you

want. Then write it all back as XHTML.


Next, each < probably needs an escape, like <




When I try that, it doesn’t replace either one of the “pre” or

“blockquote” blocks with ‘’, but the first method works perfect for the

“pre” block only.  I can’t even get the blockquote one to work by

itself.




You could run two gsubs; one with 


 and one with 
.


To strip, you could just yank all 4 items with 4 gsubs, too.


–

Phlip

Redirecting... ← NOT a blog!!!
4

On Dec 7, 2006, at 10:05 PM, Phlip wrote:

incrementally
Next, try (

|
).

reach in and nab each pre, and change its tag or contents to


You could run two gsubs; one with 


 and one with 
.


To strip, you could just yank all 4 items with 4 gsubs, too.


–

Phlip

Redirecting... ← NOT a blog!!!




If you’re trying to get rid of just the tags, then this might work.

However, if you intend to remove the content between the tags, too

(“The 
stuff doesn’t
 work” => “The  work”), then you either

need to specifically match the newlines or just use the ‘m’ modifier

on your regexp to use multi-line mode.


If you want to remove 
 and 
 along with the contents

(inner_html) of those, then you can try something like this:


irb>> regexp =  %r{<(pre|blockquote)\b[^>]>.?</\1>}m

=> /<(pre|blockquote)\b[^>]>.?</\1>/m


irb>> html_fragment = <<EOF

And then someone said:



When I try that, it doesn't replace either one of the "pre" or
"blockquote" blocks with '', but the first method works perfect for the
"pre" block only.  I can't even get the blockquote one to work by
itself.


So I told them to use this code:

   regexp = %r{<(pre|blockquote)\\b[^>]*>.*?}m
   my_string = <<-EOS
And then someone said:


When I try that, it doesn't replace either one of the "pre" or
"blockquote" blocks with '', but the first method works perfect for the
"pre" block only.  I can't even get the blockquote one to work by
itself.


   EOS
   my_string.gsub!(regexp, '...')




When I try that, it doesn't replace either one of the "pre" or
"blockquote" blocks with '', but the first method works perfect for the
"pre" block only.  I can't even get the blockquote one to work by
itself.


So I told them to use this code:

   regexp = %r{<(pre|blockquote)\\b[^>]*>.*?}m
   my_string = <<-EOS
And then someone said:


When I try that, it doesn't replace either one of the "pre" or
"blockquote" blocks with '', but the first method works perfect for the
"pre" block only.  I can't even get the blockquote one to work by
itself.


   EOS
   my_string.gsub!(regexp, '...')


EOF
=> "And then someone said:\n
\nWhen I try that, it doesn't
replace either one of the \"pre\" or\n\"blockquote\" blocks with '',
but the first method works perfect for the\n\"pre\" block only.  I
can't even get the blockquote one to work by\nitself.\n

\nSo I told them to use this code:\n
\n  regexp = %
r{<(pre|blockquote)\\b[^>]*>.*?}m\n  my_string = <<-EOS\nAnd
then someone said:\n
\nWhen I try that, it doesn't replace
either one of the \"pre\" or\n\"blockquote\" blocks with '', but the
first method works perfect for the\n\"pre\" block only.  I can't even
get the blockquote one to work by\nitself.\n
\n  EOS\n
my_string.gsub!(regexp, '...')\n
\n"

irb>> html_fragment.gsub(regexp, ‘…’)

=> “And then someone said:\n…\nSo I told them to use this code:\n…

\n”


irb>> puts _

And then someone said:

…

So I told them to use this code:

…

=> nil


irb>>


In addition to using an XML parser as Philip suggests, you might want

to actually read about regular expressions.  You can start with the

pickaxe (Programming Ruby, The Pragmatic Programmers’ Guide, 2nd ed.)

pages 68-70, 324-328, 600-603.


-Rob


Rob B.		http://agileconsultingllc.com

[email protected]
5

Ryan,

I agree with Phlip. This has crossed into territory better served by a
real HTML parser. Something like this (untested):

require ‘hpricot’
doc =
Hpricot(“Keep

Toss
Keep
Toss

Toss

Toss
”)

doc.search("//pre").each do |pre|
pre.remove
end

doc.search("//blockquote").each do |bq|
bq.remove
end

puts doc