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 -"

Answer 1

Here's an elegant solution to your problem:

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

Answer 2

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 -"