# Test content string with regex **URL:** \ **Category:** Ruby\ **Created:** [November 19, 2006, 10:20pm UTC](https://www.ruby-forum.com/t/test-content-string-with-regex/76513 "2006-11-19T22:20:58Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![jeanluca](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/74df32/32.png) [@jeanluca](https://www.ruby-forum.com/u/jeanluca)\ **Post date:** [November 19, 2006, 10:20pm UTC](https://www.ruby-forum.com/t/test-content-string-with-regex/76513/1 "2006-11-19T22:20:58Z")
Hi All I just tried to test the content of a string, something like this: c = “1234AA” if c.scan( /1234567890/ ) p “OK” else p “NO” end This always returns “OK” ☹ Any suggestions what goes wrong here. And is this the way to check the content of a string ? Thanks a lot LuCa ---
**Author:** ![jeanluca](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/74df32/32.png) [@jeanluca](https://www.ruby-forum.com/u/jeanluca)\ **Post date:** [November 20, 2006, 9:19am UTC](https://www.ruby-forum.com/t/test-content-string-with-regex/76513/2 "2006-11-20T09:19:20Z")
Luca S. wrote: > Hi All > > I just tried to test the content of a string, something like this: > > c = “1234AA” > > if c.scan( /1234567890/ ) > p “OK” > else > p “NO” > end > > This always returns “OK” ☹ > > Any suggestions what goes wrong here. And is this the way to check the > content of a string ? > > Thanks a lot > LuCa (i think) the reason you always get OK, is because the if c.scan always returns a true value (the scan method always takes place) (i.e, it never returns nil/false)…i don’t know exactly what method you need, but first of all check out [http://rubycentral.com/book/ref\_c\_string.html#String.scan](http://rubycentral.com/book/ref_c_string.html#String.scan) to see that it returns either an array or a string, and second of all maybe, check out, Regexp#=~ , maybe that is better? hth, harp ---
**Author:** ![jeanluca](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/74df32/32.png) [@jeanluca](https://www.ruby-forum.com/u/jeanluca)\ **Post date:** [November 20, 2006, 2:45pm UTC](https://www.ruby-forum.com/t/test-content-string-with-regex/76513/3 "2006-11-20T14:45:46Z")
“Luca S.” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote in message news:removed\_email\_address@domain.invalid… > p “NO” > > – because of this irb(main):008:0\> a=c.scan( /1234567890/ ) =\> [] c.scan is returning an empty array, not nil, so your ‘if’ statement passes. I prefer to do a regex for what you seem to be trying to do. if (c =~(/1234567890/ )) then or if((index=c=~/23211/)) then =~ returns nil for no match. Otherwise you get the index of the content. Jared [http://jaredrichardson.net](http://jaredrichardson.net) ---
**Author:** ![jeanluca](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/74df32/32.png) [@jeanluca](https://www.ruby-forum.com/u/jeanluca)\ **Post date:** [November 20, 2006, 2:46pm UTC](https://www.ruby-forum.com/t/test-content-string-with-regex/76513/4 "2006-11-20T14:46:24Z")
Luca S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > p “NO” > end > > This always returns “OK” ☹ > > Any suggestions what goes wrong here. And is this the way to check the > content of a string ? What exactly do you want to check? If you want to make sure that a string solely consists of digits this is what you would do: c = “1234AA” if /\A\d+\z/ =~ c puts “ok” else puts “nok” end Kind regards ``` robert ``` ---
**Author:** ![jeanluca](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/74df32/32.png) [@jeanluca](https://www.ruby-forum.com/u/jeanluca)\ **Post date:** [November 20, 2006, 2:45pm UTC](https://www.ruby-forum.com/t/test-content-string-with-regex/76513/5 "2006-11-20T14:45:50Z")
Alle 22:21, domenica 19 novembre 2006, Luca S. ha scritto: > p “NO” > end > > This always returns “OK” ☹ > > Any suggestions what goes wrong here. And is this the way to check the > content of a string ? > > Thanks a lot > LuCa Even when there’s no match, String#scan returns an array, so your is always true. To make it work, you should use if !c.scan(/1234567890/).empty? As for your second question, it depends on what exactly you want to do. It is the correct form if you need to get all the numbers in the string, regardless of their position or any other thing (by the way, if you want to match a digit in a regexp, you can use /\d/). If you simply want to check whether the string contains a digit, you can use String#match or =~ with the /\d/ regexp. If you need more control on the scanning, you can use the StringScanner class. I hope this helps Stefano ---
**Author:** ![jeanluca](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/74df32/32.png) [@jeanluca](https://www.ruby-forum.com/u/jeanluca)\ **Post date:** [November 21, 2006, 3:14am UTC](https://www.ruby-forum.com/t/test-content-string-with-regex/76513/6 "2006-11-21T03:14:38Z")
Bernard K. wrote: > this is a ruby gotcha > > the only thing that returns false or false or nil > > 0 , ‘0’, ‘’’’, an empty array, or an empty hash all evaluate to true Saying it’s a “gotcha” makes it sound like the behavior is wrong. Some would say that only false should be false. Me, I like that nil is false, but I sure as hell don’t want 0 or ‘’ or [] or {} to be false. It behaves well – that’s not a gotcha – that’s just good common sense. I can’t quite tell what you’re looking for exactly, but String#match is probably it. (I don’t like the =~ perlism myself). ---
**Author:** ![jeanluca](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/74df32/32.png) [@jeanluca](https://www.ruby-forum.com/u/jeanluca)\ **Post date:** [November 21, 2006, 5:21am UTC](https://www.ruby-forum.com/t/test-content-string-with-regex/76513/7 "2006-11-21T05:21:21Z")
Hi – On Mon, 20 Nov 2006, Robert K. wrote: > > else > > solely consists of digits this is what you would do: > > c = “1234AA” > > if /\A\d+\z/ =~ c Or: unless /\D/ =~ c 🙂 David ---
**Author:** ![jeanluca](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/74df32/32.png) [@jeanluca](https://www.ruby-forum.com/u/jeanluca)\ **Post date:** [November 21, 2006, 1:32am UTC](https://www.ruby-forum.com/t/test-content-string-with-regex/76513/8 "2006-11-21T01:32:57Z")
----- Original Message ----- From: “Jared R.” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Newsgroups: comp.lang.ruby To: “ruby-talk ML” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Sent: Sunday, November 19, 2006 4:45 PM Subject: Re: test content string with regex > > if c.scan( /1234567890/ ) > > c.scan is returning an empty array, not nil, so your ‘if’ statement > Jared > [http://jaredrichardson.net](http://jaredrichardson.net) > > the OP asked why it was always true this is a ruby gotcha the only thing that returns false or false or nil 0 , ‘0’, ‘’‘’, an empty array, or an empty hash all evaluate to true ---
**Author:** ![jeanluca](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/74df32/32.png) [@jeanluca](https://www.ruby-forum.com/u/jeanluca)\ **Post date:** [November 21, 2006, 5:23am UTC](https://www.ruby-forum.com/t/test-content-string-with-regex/76513/9 "2006-11-21T05:23:22Z")
Hi – On Tue, 21 Nov 2006, El Gato wrote: > false, but I sure as hell don’t want 0 or ‘’ or [] or {} to be false. > It behaves well – that’s not a gotcha – that’s just good common sense. > > I can’t quite tell what you’re looking for exactly, but String#match is > probably it. (I don’t like the =~ perlism myself). I don’t either, but I’ve reluctantly had to accept that it’s faster than #match, at least in the comparisons I’ve seen. Of course that doesn’t matter unless it matters, so to speak. David