script or utility to transform a string w embedded spaces into a sym

I need to transform strings like "Instructor ID" or "Lovely Ice tree"
into sym :instructor_id , :lovely_ice_tree
I tried to do the following :
downcase all string components the unique the spaces and replace w an
underscore

is there a better and faster way to do it ?

thanks fy feedback

string.downcase.tr(' ', '_')

maybe.

I have a little monkey-patch called "dehumanize" which is *almost*
what you want:

module ActiveSupport::Inflector
  # does the opposite of humanize.... mostly. Basically does a
  # space-substituting .underscore
  def dehumanize(string_value)
    result = string_value.to_s.dup
    result.downcase.gsub(/ +/,'_')
  end
end
class String
  def dehumanize
    ActiveSupport::Inflector.dehumanize(self)
  end
end

you could then call:
  String.dehumanize.to_sym

Thanks , I'll use this patch ..

thanks , part of the solution as per Michael's patch