Identify extract & replace part of a string in ruby

Question

I've been having difficulty trying to figureout how to go about solving this issue. I have 2 kinds of URLs in which I need to be able to update/increment the number value for the page.

Url 1:

forum-351-page-2.html

In the above, I would like to modify this url for n pages. So I'd like to generate new urls with a given range of say page-1 to page-30. But that's all I'd like to change. page-n.html

Url 2:

href="forumdisplay.php?fid=115&page=3

The second url is different but I feal it's easier visit.

Cary Swoveland · Accepted Answer · 2016-11-02 03:05:16Z

1

R = /
    (?:             # begin non-capture group
      (?<=-page-)   # match string in a positive lookbehind
      \d+           # match 1 or more digits
      (?=\.html)    # match period followed by 'html' in a positive lookahead
    )               # close non-capture group
    |               # or
    (?:             # begin non-capture group
      (?<=&page=)   # match string in a positive lookbehind
      \d+           # match 1 or more digits
      \z            # match end of string
    )               # close non-capture group
    /x              # free-spacing regex definition mode

def update(str, val)
  str.sub(R, val.to_s)
end

update("forum-351-page-2.html", 4)
  #=> "forum-351-page-4.html"
update("forumdisplay.php?fid=115&page=3", "4")
  #=> "forumdisplay.php?fid=115&page=4"

edited Nov 2, 2016 at 3:05

answered Nov 2, 2016 at 1:45

Cary Swoveland

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2 Comments

Doublespeed Over a year ago

+1 Thank you this is awesome. Thank you for breaking down the way this works. What's a good resource I can use to learn Regex in Ruby? With problems/solutions so I can practice? I'm sadly oblivious to it.

Cary Swoveland Over a year ago

You might want to have a look at this tutorial.

davidhu · Accepted Answer · 2016-11-02 01:16:06Z

1

For the first url

url1 = "forum-351-page-2.html"

(1..30).each do |x|
  puts url1.sub(/page-\d*/, "page-#{x}")
end

This will output

"forum-351-page-1.html"
"forum-351-page-2.html"
"forum-351-page-3.html"
...
"forum-351-page-28.html"
"forum-351-page-29.html"
"forum-351-page-30.html"

You can do the same thing for the second url.

url1.sub(/page=\d*$/, "page=#{x}")

answered Nov 2, 2016 at 1:16

davidhu

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1 Comment

Doublespeed Over a year ago

+1 for the simplicity. I gave the other answer the win since it breaks down the regex individual pieces. Thank you for your help.

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