String manipulation in Ruby

Question

Given an array :

1.9.2p290 :172 >   tags_array = %w[one two]
 => ["one", "two"] 
1.9.2p290 :173 >

how can operate on it to have back (exactly) the following String ?

[/^one/i, /^two/i]

... i get a try with this :

1.9.2p290 :173 > tags_array.collect! {|tag| "/^"+tag+"/i"}
 => ["/^one/i", "/^two/i"] 
1.9.2p290 :174 >

but I really want [/^one/i, /^two/i] without double quote.

Your expected result doesn't appear to be a string, but an array of regexps. You actual result is also an array of strings, not a string. Can you clarify? — Andrew Marshall
– Andrew Marshall, Commented May 10, 2012 at 22:28
forget any structure, due the first array I want a string back, the string will be composed by each element of the sourcing array, surrounded by the regexes chars (case-insensitive) ... — Luca G. Soave
– Luca G. Soave, Commented May 10, 2012 at 22:33

Pete · Accepted Answer · 2012-05-10 22:31:42Z

4

If you want an array of regexps, you can use string interpolation within a regex literal:

%w[one two].map { |tag| /^#{tag}/i }

answered May 10, 2012 at 22:31

Pete

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Comments

Alberto Moriconi · Accepted Answer · 2012-05-10 22:30:53Z

1

You have to map Regexp::new:

tag_array.collect! { |tag| Regexp.new("^#{tag}", true) }
=> [/^one/i, /^two/i]

Notice true is passed as second parameter to Regexp::new: it means the resulting regular expression should be case insensitive.

answered May 10, 2012 at 22:30

Alberto Moriconi

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2 Comments

Luca G. Soave Over a year ago

I get this back : 1.9.2p290 :187 > tags_array = %w[one two] => ["one", "two"] 1.9.2p290 :188 > tag_array.collect! { |tag| Regexp.new("^#{tag}", true) } => [/^(?i-mx:^(?i-mx:^one))/i, /^(?i-mx:^(?i-mx:^two))/i] 1.9.2p290 :189 >

Alberto Moriconi Over a year ago

That's because you invoked it on an Array that already contained two Regexp objects ;) My answer is just the same as the one the other user supplied, with the only difference i used the explicit constructor: try it on the ["one", "two"] array and it will work just fine.

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