Inserting a Variable into a String using Regex - Ruby

Question

I'm having trouble inserting an outside variable into a string using regular expressions.

I have a string which looks like:

    string = "7  -"

And I want to insert a integer as a string into the space between the "7" and the "-", and I've tried to use interpolation, like so:

    variable = "15"
    string = string.gsub(/(\S?\d+)(\s)(\s)(\D)/, '\1\2#{variable}\3\4')

(the \S? is to account for any " - " attached to a digit for whether it is positive or negative)

The output is a string looking like this:

    "7 \#{variable} -"

But I want the output to look like this:

    "7 15 -"

MrPizzaFace · Accepted Answer · 2014-01-26 04:53:23Z

1

Here's an elegant solution to your problem:

s = "7  -"
v = 15
string = s.gsub(/\d\s/, "#{s.delete("-").strip} #{v}")
#=> "7 15 -"

answered Jan 26, 2014 at 4:53

MrPizzaFace

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2 Comments

Nick Meehan Over a year ago

How would delete and strip work in this case? I'm having a tough time following along.

MrPizzaFace Over a year ago

s.delete("-").strip is: delete is removing the hyphen and strip is removing the white space from the instance of s as is: s = "7 -" The space is returned to the string here: ...ip}_\s_#{v}" Understand?

falsetru · Accepted Answer · 2014-01-26 04:20:08Z

0

Use double quote. Single-quoted string does not interpolate.

string = "7  -"
variable = "15"
string = string.gsub(/(\S?\d+)(\s)(\s)(\D)/, "\\1\\2#{variable}\\3\\4")
string # => "7 15 -"

answered Jan 26, 2014 at 4:20

falsetru

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1 Comment

Nick Meehan Over a year ago

Works like a charm, thanks! I'm just learning Ruby, and usually use double quotes. Is it best practice to use double quotes most times? Or just when dealing with regex?

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