Ruby - Regex String Insertion

Question

I need to substitute the value of a string into my regular expression in Ruby. Is there an easy way to do this? For example:

foo = "0.0.0.0"
goo = "here is some other stuff 0.0.0.0" 
if goo =~ /foo's value goes here/
  puts "success!"
end

Answer 1

Use Regexp.new:

if goo =~ Regexp.new(foo) # Evaluates to /0.0.0.0/

Answer 2

probably Regexp.escape(foo) would be a starting point, but is there a good reason you can't use the more conventional expression-interpolation "my stuff #{mysubstitutionvariable}"?

Also, you can just use !goo.match(foo).nil? with a literal string.

Answer 3

Regex.compile(Regex.escape(foo))

Answer 4

Same as string insertion.

if goo =~ /#{Regexp.quote(foo)}/
#...

Answer 5

foo = "0.0.0.0"
goo = "here is some other stuff 0.0.0.0" 

puts "success!" if goo =~ /#{foo}/

Answer 6

Note that the Regexp.quote in Jon L.'s version is important!

if goo =~ /#{Regexp.quote(foo)}/

If you just do the "obvious" version:

if goo =~ /#{foo}/

then the periods in your match text are treated as regexp wildcards, and "0.0.0.0" will match "0x0y0z"...

Note also that if you really just want to check for a substring match, you can simply do

if goo.include?(foo)

which doesn't require an additional quoting or worrying about special characters...