Regular expression not working when put in an object

Question

Hi!

I'm trying to store regexes in a database but they're not working when used in a .sub(), even though the same regex works when used directly in .sub() as a string.

regex = Class.object.field  // Class.object is an active record containing "\w*\s\/\s"
mystring = "first / second"

mystring.sub(/#{regex}/, '')
// => nil

mystring.sub(/\w*\s\/\s/, '') 
// => second

Any insight appreciated!

Thanks, Matt.

Editing to correct class/object terminology (thanks) & correcting my 2nd example as I had shown #{} wrapped around the working regex (cut & paste SNAFU).

Answer 1

A String is not a Regexp. You have to create a Regexp object first.

regex = Regexp.new("\w*\s\/\s")

Answer 2

To answer your question: It is not quite what kind of thing your Class.object is. If it's an ActiveRecord, it won't work.

Edit: You obviously found that the problem is Rails escaping the regexp.

An ActiveRecord cannot "contain" your regular expression directly; the regexp will be in one of the fields of your record. In which case you'd want to do something like regexp = Class.object.field_containing_the_regexp.

Even if that is not the case, I suspect that the problem is that your regexp is something other than a string. You can quickly test this by using

puts "My regexp: #{regexp}"

The string that you will see in the output will be the one that is used for the regexp.

Answer 3

Turns out my regexp didn't cater for all cases - \w didn't account for symbols. After checking in rails console, and seeing the screwey escaping I was alreasdy half-way down the wrong track.

Thanks for the help.