I am trying to figure out how I can filter out key and value pairs from one filter into another For example I want to take this hash x = { "one" => "one", "two" => "two", "three" => "three"} y = x.some_function y == { "one" => "one", "two" => "two"} Thanks for your help EDIT: should probably mention that in this example, I want it to behave as a whitelist filter. That is, I know what I want, not w