Return substring from map variable using Ruby

Question

I have one variable that comes from a map, I'm trying to get a specific part between square brackets

(e.g."dmfkdmfk[IWANTTHISPART]mlkm")

but it isn't working by the way I did. I'm trying as same way used here.

Original Code:

query_values = activities.map do |activity|
  '(' +
  "#{activity['note']}"
  +')'

end

I tried:

query_values = activities.map do |activity|
  '(' +
  "#{activity['note'].[/#{"["}(.*?)#{"]"}/m, 1]}" 
  +')'

end

Error log:

syntax error, unexpected '[', expecting '('
      '(' + "#{activity['note'].[/#{"["}(.*?)#{"]"}/m, 1]},""'" +')'
                                 ^
quase.rb:40: syntax error, unexpected keyword_end, expecting tSTRING_DEND

How can I go through? Many Thanks.

It's unclear what relevance the "Original Code" has to the question. Is that also non-working code that you tried? Keep n mind that we're not supposed to have to follow any links to understand the question, if there is additional information in the link that would clarify the question, it's best to edit that information into the question itself. — Wayne Conrad
– Wayne Conrad, Commented May 19, 2016 at 12:50
@WayneConrad Original code is the one working but not implemented the question issue. — Julinho da Adelaide
– Julinho da Adelaide, Commented May 19, 2016 at 16:57

Cary Swoveland · Accepted Answer · 2016-05-19 06:55:35Z

6

str = "(dmfkdmfk[IWANTTHISPART]mlkm)"

#1 Use a regex with lookarounds

R0 = /
     (?<=\[) # match a left bracket in a positive lookbehind
     .+      # match one or more of any character
     (?=\])  # match a right bracket in a positive lookahead
     /x      # free-spacing regex definition mode

(same as R0 = /(?<=\[).+(?=\])/)

str[R0] #=> "IWANTTHISPART"

#2 Split string on a left or right bracket

R1 = /
     [\[\]] # match a left or right bracket
     /x

(same as R1 = /[\[\]]/)

str.split(R1)[1]
  #=> "IWANTTHISPART"

#3 No regex

str[str.index('[')+1..str.index(']')-1]
  #=> "IWANTTHISPART"

edited May 19, 2016 at 6:55

answered May 19, 2016 at 3:39

Cary Swoveland

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1 Comment

tadman Over a year ago

Could also use scan here to find all instances of things inside square brackets.

sawa · Accepted Answer · 2016-05-19 01:35:27Z

2

You cannot have a period after the receiver when using [] in its syntax-sugar form. The following is ungrammatical:

string.[regex, parameter]

Use either the ordinary method invocation form:

string.[](regex, parameter)

or the syntax-sugar form:

string[regex, parameter]

edited May 19, 2016 at 1:35

answered May 19, 2016 at 1:30

sawa

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4 Comments

Julinho da Adelaide Over a year ago

But how can I use this? I'm not sure how to use the regex.

sawa Over a year ago

@JulinhodaAdelaide You already have a regex. Aren't you trying to use that? The parameter can follow the regex.

Julinho da Adelaide Over a year ago

Does it work with map variable? I tried it all way but no success. Can you help me?

sawa Over a year ago

"#{activity['note'][/#{"["}(.*?)#{"]"}/m, 1]}"

Mori · Accepted Answer · 2016-05-19 01:32:59Z

1

/\[(.*)\]/.match( "dmfkdmfk[IWANTTHISPART]mlkm" )[1]
=> "IWANTTHISPART"

answered May 19, 2016 at 1:32

Mori

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4 Comments

Julinho da Adelaide Over a year ago

Should I use like : ""' /[(.*)]/.match( #{activity['type']} )[1]""' ??

Mori Over a year ago

@JulinhodaAdelaide, learn by trying! Your Rails console or IRB can answer that as fast as you can type it.

tadman Over a year ago

@JulinhodaAdelaide There's also Rubular which is handy for debugging regular expressions.

Cary Swoveland Over a year ago

Good answer. A variant (which I don't like as well) is ("dmfkdmfk[IWANTTHISPART]mlkm" =~ /\[(.*)\]/) && $1.

Gagan Gami · Accepted Answer · 2016-05-19 04:51:41Z

1

You can use String#[] with a regular expression:

> a = "dmfkdmfk[IWANTTHISPART]mlkm"
> a[/\[.*?\]/][1..-2]
#=> "IWANTTHISPART"

answered May 19, 2016 at 4:51

Gagan Gami

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