# Regular expressions in Ruby on rails

**URL:** <https://www.ruby-forum.com/t/regular-expressions-in-ruby-on-rails/73372>\
**Category:** Rails\
**Created:** [October 24, 2006, 8:23am UTC](https://www.ruby-forum.com/t/regular-expressions-in-ruby-on-rails/73372 "2006-10-24T08:23:31Z")\
**Posts on this page:** 8\
**Page:** 1

<div class="post-metadata">

**Author:** ![darrenevans](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/87869e/32.png) [@darrenevans](https://www.ruby-forum.com/u/darrenevans)\
**Post date:** [October 24, 2006, 8:23am UTC](https://www.ruby-forum.com/t/regular-expressions-in-ruby-on-rails/73372/1 "2006-10-24T08:23:31Z")

</div>

Hi

I hope that it is OK to post this here, please say if not…

I’m pretty new to ruby and regular expressions. I would like to use a  
regular expression to match only numbers contained within square  
brackets. e.g. a sentence may be…

[1] to [2], corresponding to [3] to [4] output using IRP 829 Version  
2XX, [5] to [6] output using IRP 452 Version 3XX

The numbers are refences to specifications in another table. At the  
moment, I use /[\d\*]/ This extracts the numbers including brackets,  
but now can I just extract the numbers by altering the expression? The  
full ruby code I use for this is as follows if this is any use, probably  
also there is a better way than splitting on a space…

Any help would be great and really appreciated.

Many thanks

Darren

\<%if (opt==“display”)%\>  
\<%cycles = 1  
n = 0  
@text\_line = “”  
for part in @translation.text\_line.split(’ ')  
if ((/[\d\*]/).match(part))  
if (@fields[n])  
@unit=@specification.get\_unit(@fields[n].unit\_id).name  
@prefix\_new=@specification.get\_prefix(@fields[n].prefix\_id).name

```
        if (@translation.text_line.split(' ').size==cycles)
            @text_line = "#{@text_line}"+"#{@fields[n].result}"+" 

```

“+”#{@prefix\_new}"+"#{@unit}"  
else  
@text\_line = “#{@text\_line}”+"#{@fields[n].result}"+"  
“+”#{@prefix\_new}"+"#{@unit}"+" "  
end  
end  
n += 1  
else  
if (@translation.text\_line.split(’ ').size==cycles)  
@text\_line = @text\_line+"#{part}"  
else  
@text\_line = @text\_line+"#{part}"+" "  
end  
end  
cycles += 1  
end  
end%\>

---

<div class="post-metadata">

**Author:** ![darrenevans](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/87869e/32.png) [@darrenevans](https://www.ruby-forum.com/u/darrenevans)\
**Post date:** [October 24, 2006, 8:46am UTC](https://www.ruby-forum.com/t/regular-expressions-in-ruby-on-rails/73372/2 "2006-10-24T08:46:37Z")

</div>

On Tue, Oct 24, 2006 at 08:23:31AM +0200, Darren E. wrote:

> 2XX, [5] to [6] output using IRP 452 Version 3XX
> 
> The numbers are refences to specifications in another table. At the  
> moment, I use /[\d\*]/ This extracts the numbers including brackets,  
> but now can I just extract the numbers by altering the expression? The  
> full ruby code I use for this is as follows if this is any use, probably  
> also there is a better way than splitting on a space…
> 
> Any help would be great and really appreciated.

use () around the part of the match you want to extract, i.e.

if part =~ /[(\d\*)]/  
puts $1 # $2 would mean the second group of (), and so on  
else  
…  
end

btw, you really should get that code out of your view, and put it  
into a helper or model…

Jens

–  
Jens Krämer  
removed\_email\_address@domain.invalid

---

<div class="post-metadata">

**Author:** ![darrenevans](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/87869e/32.png) [@darrenevans](https://www.ruby-forum.com/u/darrenevans)\
**Post date:** [October 24, 2006, 10:43am UTC](https://www.ruby-forum.com/t/regular-expressions-in-ruby-on-rails/73372/3 "2006-10-24T10:43:56Z")

</div>

Jens

Thank you very much. I am not that good at sticking to the rules of Ruby  
on Rails and have probably suffered as a result. I have moved this to a  
model.

The regular expression works well for long series as I require. However,  
it does not work for ([1]) for example. I would like to say "ignore  
everything before and after the square brackets.

Does anyone have any ideas how to do this? I have tried a lot of  
symbols, but often I am not allowed to put these at the start.

Many thanks

Darren

Jens K. wrote:

> On Tue, Oct 24, 2006 at 08:23:31AM +0200, Darren E. wrote:
> 
> > 2XX, [5] to [6] output using IRP 452 Version 3XX
> > 
> > The numbers are refences to specifications in another table. At the  
> > moment, I use /[\d\*]/ This extracts the numbers including brackets,  
> > but now can I just extract the numbers by altering the expression? The  
> > full ruby code I use for this is as follows if this is any use, probably  
> > also there is a better way than splitting on a space…
> > 
> > Any help would be great and really appreciated.
> 
> use () around the part of the match you want to extract, i.e.
> 
> if part =~ /[(\d\*)]/  
> puts $1 # $2 would mean the second group of (), and so on  
> else  
> …  
> end
> 
> btw, you really should get that code out of your view, and put it  
> into a helper or model…
> 
> Jens
> 
> –  
> Jens Krä­¥r  
> removed\_email\_address@domain.invalid

---

<div class="post-metadata">

**Author:** ![darrenevans](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/87869e/32.png) [@darrenevans](https://www.ruby-forum.com/u/darrenevans)\
**Post date:** [October 24, 2006, 7:09pm UTC](https://www.ruby-forum.com/t/regular-expressions-in-ruby-on-rails/73372/4 "2006-10-24T19:09:48Z")

</div>

Darren E. wrote:

> The regular expression works well for long series as I require. However,  
> it does not work for ([1]) for example. I would like to say "ignore  
> everything before and after the square brackets.

Um … yes it does?

irb(main):001:0\> part = ‘([1])’  
=\> “([1])”  
irb(main):002:0\> part  
=\> “([1])”  
irb(main):003:0\> if part =~ /[(\d\*)]/  
irb(main):004:1\> puts $1  
irb(main):005:1\> end  
1  
=\> nil  
irb(main):006:0\>

Maybe you should post your actual model code so we can try to see why it  
isn’t working for you …

---

<div class="post-metadata">

**Author:** ![darrenevans](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/87869e/32.png) [@darrenevans](https://www.ruby-forum.com/u/darrenevans)\
**Post date:** [October 25, 2006, 7:52am UTC](https://www.ruby-forum.com/t/regular-expressions-in-ruby-on-rails/73372/5 "2006-10-25T07:52:34Z")

</div>

Hi

Then the problem as I see it is with the split, but I don’t know how to  
overcome this. Because of the way the split is handled

[1] - ([2]) corresponding to [3] to [4] output using IQS 452 Version 2XX  
[5] to [6] output using IQS 452 Version 3XX

(stored in the database) becomes

[1] - [2] corresponding to [3] to [4] output using IQS 452 Version 2XX  
[5] to [6] output using IQS 452 Version 3XX

Due to inadequacies in my model.

The second line is a text line displayed (so the user can see what the  
final output will be with specifications and units included), but of  
course the way I do it the brackets around the [2] have disappeared

What I want to do is to take the top line and just replace the [value]  
part but leave the brackets (could be anything else too, a comma, full  
stop etc).

The important view part is as follows:

```
<%unless @translation.text_line.nil?%>
 <%@text_line=@specification.display_text_line(@translation, 

```

@specification, @fields)%\>

##### \<%if (@translation.level==1)%\>**\<%end%\> \<%if (@translation.level==2)%\>\<%end%\> \<%if (@translation.level==3)%\>\<%end%\> \<%if (@translation.level==4)%\>- \<%end%\> \<%if (@translation.level==5)%\>&nbsp - &nbsp\<%end%\> \<%if (@translation.level==6)%\>**
_\<%end%\>  
\<%if (@translation.level==7)%\>\<%if  
 @mode!=“list”%\>\<%else%\>\<%end%\>\<%end%\>  
\<%=@translation.section%\>  
\<%if ((@translation.level==3) || (@translation.level==4) ||  
(@translation.level==5))%\>:&nbsp\<%end%\>  
\<%=@text\_line%\>_

```
 <%end%>

```

Probably, only the part @text\_line is important, the rest is format  
stuff. The model is as follows:

def display\_text\_line(translation, specification, fields)  
cycles = 1  
n = 0  
text\_line = “”  
for part in translation.text\_line.split(’ ')  
if /[(\d\*)]/.match(part)  
if (fields[n])

```
        @unit=specification.get_unit(fields[n].unit_id).name
        @prefix_new=specification.get_prefix(fields[n].prefix_id).name
        if (translation.text_line.split(' ').size==cycles)
            text_line = "#{text_line}"+"#{fields[n].result}"+" 

```

“+”#{@prefix\_new}"+"#{@unit}"  
else  
text\_line = “#{text\_line}”+"#{fields[n].result}"+"  
“+”#{@prefix\_new}"+"#{@unit}"+" "  
end  
end  
n += 1  
else  
if (translation.text\_line.split(’ ').size==cycles)  
text\_line = text\_line+"#{part}"  
else  
text\_line = text\_line+"#{part}"+" "  
end  
end  
cycles += 1  
end  
return text\_line  
end

I hope that someone can help with this, I have tried a lot, but have  
failed to resolve this.

Regards

Darren

Chris G. wrote:

> Darren E. wrote:
> 
> > The regular expression works well for long series as I require. However,  
> > it does not work for ([1]) for example. I would like to say "ignore  
> > everything before and after the square brackets.
> 
> Um … yes it does?
> 
> irb(main):001:0\> part = ‘([1])’  
> =\> “([1])”  
> irb(main):002:0\> part  
> =\> “([1])”  
> irb(main):003:0\> if part =~ /[(\d\*)]/  
> irb(main):004:1\> puts $1  
> irb(main):005:1\> end  
> 1  
> =\> nil  
> irb(main):006:0\>
> 
> Maybe you should post your actual model code so we can try to see why it  
> isn’t working for you …

---

<div class="post-metadata">

**Author:** ![darrenevans](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/87869e/32.png) [@darrenevans](https://www.ruby-forum.com/u/darrenevans)\
**Post date:** [October 26, 2006, 8:05am UTC](https://www.ruby-forum.com/t/regular-expressions-in-ruby-on-rails/73372/6 "2006-10-26T08:05:43Z")

</div>

Hi

I have got to the stage where if I take the string (example):

sadfas112f([1]),fds121a

I want to extract everything after the somenumber]

To do this I have at the moment:

/\D\*$/.match(part)[0]

This gives:

]),fds121a

Now all I want to do is tell the regular expression to ignore the “]”,  
then I’m there. Does anyone know how to “ignore” a “]”.

Many thanks for your help.

Darren

Darren E. wrote:

> Hi
> 
> Then the problem as I see it is with the split, but I don’t know how to  
> overcome this. Because of the way the split is handled
> 
> [1] - ([2]) corresponding to [3] to [4] output using IQS 452 Version 2XX  
> [5] to [6] output using IQS 452 Version 3XX
> 
> (stored in the database) becomes
> 
> [1] - [2] corresponding to [3] to [4] output using IQS 452 Version 2XX  
> [5] to [6] output using IQS 452 Version 3XX
> 
> Due to inadequacies in my model.
> 
> The second line is a text line displayed (so the user can see what the  
> final output will be with specifications and units included), but of  
> course the way I do it the brackets around the [2] have disappeared
> 
> What I want to do is to take the top line and just replace the [value]  
> part but leave the brackets (could be anything else too, a comma, full  
> stop etc).
> 
> The important view part is as follows:
> 
> ```
> <%unless @translation.text_line.nil?%>
> <%@text_line=@specification.display_text_line(@translation, 
> 
> ```
> 
> @specification, @fields)%\>
> 
> ##### \<%if (@translation.level==1)%\>**\<%end%\> \<%if (@translation.level==2)%\>\<%end%\> \<%if (@translation.level==3)%\>\<%end%\> \<%if (@translation.level==4)%\>- \<%end%\> \<%if (@translation.level==5)%\>&nbsp - &nbsp\<%end%\> \<%if (@translation.level==6)%\>**
> _\<%end%\>  
> \<%if (@translation.level==7)%\>\<%if  
> @mode!=“list”%\>\<%else%\>\<%end%\>\<%end%\>  
> \<%=@translation.section%\>  
> \<%if ((@translation.level==3) || (@translation.level==4) ||  
> (@translation.level==5))%\>:&nbsp\<%end%\>  
> \<%=@text\_line%\>_
> 
> ```
> <%end%>
> 
> ```
> 
> Probably, only the part @text\_line is important, the rest is format  
> stuff. The model is as follows:
> 
> def display\_text\_line(translation, specification, fields)  
> cycles = 1  
> n = 0  
> text\_line = “”  
> for part in translation.text\_line.split(’ ')  
> if /[(\d\*)]/.match(part)  
> if (fields[n])
> 
> ```
> @unit=specification.get_unit(fields[n].unit_id).name
> @prefix_new=specification.get_prefix(fields[n].prefix_id).name
> if (translation.text_line.split(' ').size==cycles)
> text_line = "#{text_line}"+"#{fields[n].result}"+" 
> 
> ```
> 
> “+”#{@prefix\_new}"+"#{@unit}"  
> else  
> text\_line = “#{text\_line}”+"#{fields[n].result}"+"  
> “+”#{@prefix\_new}"+"#{@unit}"+" "  
> end  
> end  
> n += 1  
> else  
> if (translation.text\_line.split(’ ').size==cycles)  
> text\_line = text\_line+"#{part}"  
> else  
> text\_line = text\_line+"#{part}"+" "  
> end  
> end  
> cycles += 1  
> end  
> return text\_line  
> end
> 
> I hope that someone can help with this, I have tried a lot, but have  
> failed to resolve this.
> 
> Regards
> 
> Darren
> 
> Chris G. wrote:
> 
> > Darren E. wrote:
> > 
> > > The regular expression works well for long series as I require. However,  
> > > it does not work for ([1]) for example. I would like to say "ignore  
> > > everything before and after the square brackets.
> > 
> > Um … yes it does?
> > 
> > irb(main):001:0\> part = ‘([1])’  
> > =\> “([1])”  
> > irb(main):002:0\> part  
> > =\> “([1])”  
> > irb(main):003:0\> if part =~ /[(\d\*)]/  
> > irb(main):004:1\> puts $1  
> > irb(main):005:1\> end  
> > 1  
> > =\> nil  
> > irb(main):006:0\>
> > 
> > Maybe you should post your actual model code so we can try to see why it  
> > isn’t working for you …

---

<div class="post-metadata">

**Author:** ![darrenevans](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/87869e/32.png) [@darrenevans](https://www.ruby-forum.com/u/darrenevans)\
**Post date:** [October 26, 2006, 4:04pm UTC](https://www.ruby-forum.com/t/regular-expressions-in-ruby-on-rails/73372/7 "2006-10-26T16:04:40Z")

</div>

A regular expression like /^(._)[(\d_)](.\*)$/ will let you capture all  
three parts of the string you appear to be interested in. However, are  
you sure you will never have two sets of numbers within square brackets  
(e.g. “[3]”) that are not separated by a space (e.g.  
“abcd[1]efgh[2]ijkl”)? Because a standard regular expression match will  
only match once in a string.

An example:

## Program:

#!/usr/bin/env ruby -w

regexp = /^(._)[(\d_)](.\*)$/

part = ‘sadfas112f([1]),fds121a’  
match = regexp.match(part)  
puts “part = ‘#{part}’”  
puts “match[1] = #{match[1]}”  
puts “match[2] = #{match[2]}”  
puts “match[3] = #{match[3]}”  
puts

part = ‘sadfas112f([1]),fd[2]s121a’  
match = regexp.match(part)  
puts “part = ‘#{part}’”  
puts “match[1] = #{match[1]}”  
puts “match[2] = #{match[2]}”  
puts “match[3] = #{match[3]}”

## Output:

part = ‘sadfas112f([1]),fds121a’  
match[1] = sadfas112f(  
match[2] = 1  
match[3] = ),fds121a

part = ‘sadfas112f([1]),fd[2]s121a’  
match[1] = sadfas112f([1]),fd  
match[2] = 2  
match[3] = s121a

If you’re sure this won’t be an issue for you, then this technique  
should work. If not, you probably want to look at gsub or scan, as  
discussed in this thread: [Ruby Regexp vs Perl and C# - Ruby - Ruby-Forum](http://www.ruby-forum.com/topic/84445)

However, I have to say that the code for your model method looks very  
complicated, and I honestly can’t figure out what it is supposed to do.  
Can you describe what it is does? I (or someone else here) may be able  
to rework it into something simpler and more readable.

---

<div class="post-metadata">

**Author:** ![darrenevans](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/87869e/32.png) [@darrenevans](https://www.ruby-forum.com/u/darrenevans)\
**Post date:** [October 26, 2006, 5:12pm UTC](https://www.ruby-forum.com/t/regular-expressions-in-ruby-on-rails/73372/8 "2006-10-26T17:12:08Z")

</div>

Dear Chris

Thank you very much for this advice. I have something that works now how  
I want it to (using your regular expression), even if it’s not the  
prettiest code in the world.

I may come back later with a description of what I have done if that is  
OK with you? There must be an easier way to do this (but it is fairly  
complex anyway).

It’s my first effort with Ruby on Rails (with very limited support),  
though I do have a reasonable amount of experience with php. My code  
starts to look like php too often at the moment, I know that & will work  
on it.

Thanks again, it’s really appreciated.

Regards

Darren

Chris G. wrote:

> A regular expression like /^(._)[(\d_)](.\*)$/ will let you capture all  
> three parts of the string you appear to be interested in. However, are  
> you sure you will never have two sets of numbers within square brackets  
> (e.g. “[3]”) that are not separated by a space (e.g.  
> “abcd[1]efgh[2]ijkl”)? Because a standard regular expression match will  
> only match once in a string.
> 
> An example:
> 
> ## Program:
> 
> #!/usr/bin/env ruby -w
> 
> regexp = /^(._)[(\d_)](.\*)$/
> 
> part = ‘sadfas112f([1]),fds121a’  
> match = regexp.match(part)  
> puts “part = ‘#{part}’”  
> puts “match[1] = #{match[1]}”  
> puts “match[2] = #{match[2]}”  
> puts “match[3] = #{match[3]}”  
> puts
> 
> part = ‘sadfas112f([1]),fd[2]s121a’  
> match = regexp.match(part)  
> puts “part = ‘#{part}’”  
> puts “match[1] = #{match[1]}”  
> puts “match[2] = #{match[2]}”  
> puts “match[3] = #{match[3]}”
> 
> ## Output:
> 
> part = ‘sadfas112f([1]),fds121a’  
> match[1] = sadfas112f(  
> match[2] = 1  
> match[3] = ),fds121a
> 
> part = ‘sadfas112f([1]),fd[2]s121a’  
> match[1] = sadfas112f([1]),fd  
> match[2] = 2  
> match[3] = s121a
> 
> If you’re sure this won’t be an issue for you, then this technique  
> should work. If not, you probably want to look at gsub or scan, as  
> discussed in this thread: [Ruby Regexp vs Perl and C# - Ruby - Ruby-Forum](http://www.ruby-forum.com/topic/84445)
> 
> However, I have to say that the code for your model method looks very  
> complicated, and I honestly can’t figure out what it is supposed to do.  
> Can you describe what it is does? I (or someone else here) may be able  
> to rework it into something simpler and more readable.