Question

I need to implement some search functionality within a Rails application. Most of the stuff I have found is generally aimed at simple plain-text search. I am trying to implement something much more specific. The sort of functionality I am looking to create is this (from a C application):

http://andyc.ac/query.gif

The form just submits the data entered by the user. So I need to translate strings like “3..7” into SQL conditions for the where method e.g.

TestLine.where( "test_int >= ? and test_int <= ?", MinInt, MaxInt )

It seems like this is something that already exists somewhere. The exact format expected is not too important, as the users are not shared between the Rails and C applications. How would this be done?

Answer 1

FWIW the specific functionality you describe is actually supported directly. Well.. almost. From the docs:

A range may be used in the hash to use the SQL BETWEEN operator:

Student.where(:grade => 9..12)

Of course then it’s a matter of translating the user’s string input to a Range, which isn’t very complex, e.g.:

def str_to_range str
  str =~ /(\d+)\.\.(\d+)/

  Range.new *$~.captures.map(&:to_i)
end

It would probably make the most sense in a scope on your model. (Of course a shortcut would be to simply eval '9..12' but evaling input from the end user is a really, really bad idea.)