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**Category:** Ruby\
**Created:** [September 1, 2008, 2:14pm UTC](https://www.ruby-forum.com/t/gsub-html-sanitizer/147402 "2008-09-01T14:14:37Z")\
**Posts on this page:** 6\
**Page:** 1
**Author:**  [@chelseas](https://www.ruby-forum.com/u/chelseas)\
**Post date:** [September 1, 2008, 2:14pm UTC](https://www.ruby-forum.com/t/gsub-html-sanitizer/147402/1 "2008-09-01T14:14:37Z")
I’m new to Ruby and a bit confused about how gsub works. I’ve read the
documentation, searched ruby-forum, and tried numerous google searches,
but can’t seem to figure out how to do something that should be simple.
This is just an example, but say I have a string “apple cat flower”. I’d
like to replace all instances of the pattern “apple” with the string
“fruit,” “cat” with the string “animal,” and “flower” with the string
“plant.” Meaning I have more than 1 pattern to replace, each with a
specific string to replace.
So I want “apple cat flower” to be converted into “fruit animal plant”.
I hope this isn’t too confusing. Help is appreciated 🙂
---
**Author:**  [@chelseas](https://www.ruby-forum.com/u/chelseas)\
**Post date:** [September 1, 2008, 2:25pm UTC](https://www.ruby-forum.com/t/gsub-html-sanitizer/147402/2 "2008-09-01T14:25:37Z")
You could just chain this up to make it neater?
orig=“apple cat flower”
orig.gsub(“apple”,“fruit”).gsub(“cat”,“animal”).gsub(“flower”,“plant”)
=\> “fruit animal plant”
There might be a ‘smarter’ way of doing this: I’m only just learning
Ruby myself , but I know from other domains (“gsub” is an old ‘awk’
command for instance) that generally speaking when doing regex
search/replace stuff you would tend to actually do this in “n”
iterations rather than coming up with a complex ‘or’ regex…
Also, I know in regex you can use the ‘&’ character to mean “The
resulting matched character(s)” - but in this case you are literally
looking for three distinct patterns…so I’m not sure this is even a
possibility…
The above is just my opinion about using regexes - I would certainly
break this up into three separate gsubs: and I might be missing a trick
or two here…so wait for other posts I would say…
You could write yourself a little ‘method’ here which took two arrays
perhaps, and then iterate over one with the other ? dunno…
John
Chealsea S. wrote:
> I’m new to Ruby and a bit confused about how gsub works. I’ve read the
> documentation, searched ruby-forum, and tried numerous google searches,
> but can’t seem to figure out how to do something that should be simple.
>
> This is just an example, but say I have a string “apple cat flower”. I’d
> like to replace all instances of the pattern “apple” with the string
> “fruit,” “cat” with the string “animal,” and “flower” with the string
> “plant.” Meaning I have more than 1 pattern to replace, each with a
> specific string to replace.
>
> So I want “apple cat flower” to be converted into “fruit animal plant”.
>
> I hope this isn’t too confusing. Help is appreciated 🙂
---
**Author:**  [@chelseas](https://www.ruby-forum.com/u/chelseas)\
**Post date:** [September 1, 2008, 2:26pm UTC](https://www.ruby-forum.com/t/gsub-html-sanitizer/147402/3 "2008-09-01T14:26:50Z")
[TYPO correction: I didn’t mean to quote ‘method’ in my reply…I was in
the middle of editing and pressed send to quick , sorry for any
confusion]
---
**Author:**  [@chelseas](https://www.ruby-forum.com/u/chelseas)\
**Post date:** [September 1, 2008, 2:31pm UTC](https://www.ruby-forum.com/t/gsub-html-sanitizer/147402/4 "2008-09-01T14:31:19Z")
2008/9/1 Chealsea S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid):
> So I want “apple cat flower” to be converted into “fruit animal plant”.
>
> I hope this isn’t too confusing. Help is appreciated 🙂
As long as the number of strings is not too large you can use
Regexp.union:
irb(main):004:0\> replacements =
{“apple”=\>“fruit”,“cat”=\>“animal”,“flower”=\>“plant”}
=\> {“cat”=\>“animal”, “apple”=\>“fruit”, “flower”=\>“plant”}
irb(main):005:0\> Regexp.union replacements.keys
=\> /cat|apple|flower/
irb(main):006:0\> “apple cat
flower”.gsub(Regexp.union(replacements.keys)) {|m| replacements[m]}
=\> “fruit animal plant”
If the number increases you probably rather want something like this
irb(main):007:0\> “apple cat flower”.gsub(/\w+/) {|m| replacements[m] ||
m}
=\> “fruit animal plant”
Kind regards
robert
---
**Author:**  [@chelseas](https://www.ruby-forum.com/u/chelseas)\
**Post date:** [September 1, 2008, 2:50pm UTC](https://www.ruby-forum.com/t/gsub-html-sanitizer/147402/5 "2008-09-01T14:50:49Z")
Thanks everyone for the replies. They were extremely useful.
---
**Author:**  [@chelseas](https://www.ruby-forum.com/u/chelseas)\
**Post date:** [September 1, 2008, 2:31pm UTC](https://www.ruby-forum.com/t/gsub-html-sanitizer/147402/6 "2008-09-01T14:31:55Z")
On Mon, Sep 1, 2008 at 2:09 PM, Chealsea S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:
> So I want “apple cat flower” to be converted into “fruit animal plant”.
>
> I hope this isn’t too confusing. Help is appreciated 🙂
If you don’t mind a loop, you could gsub each pattern one at a time.
irb(main):002:0\> patterns = {“apple” =\> “fruit”, “cat” =\> “animal”,
“flower” =\> “plant”}
=\> {“cat”=\>“animal”, “apple”=\>“fruit”, “flower”=\>“plant”}
irb(main):003:0\> s = “apple cat flower”
=\> “apple cat flower”
irb(main):004:0\> patterns.each {|p,r| s.gsub!(p, r)}
=\> {“cat”=\>“animal”, “apple”=\>“fruit”, “flower”=\>“plant”}
irb(main):005:0\> s
=\> “fruit animal plant”
You could also build a big regexp and let gsub do the loop:
irb(main):008:0\> s = “apple cat flower”
=\> “apple cat flower”
irb(main):009:0\> re = Regexp.new(“(#{patterns.keys.join(”|“)})”)
=\> /(cat|apple|flower)/
irb(main):010:0\> s.gsub(re) {patterns[$1]}
=\> “fruit animal plant”
Hope this helps,
Jesus.