Question

Well this seems like it should be a simple thing but I can’t seem to find what I need. Currently I have two variables: frequency and period. frequency is set to a number (eg 1) and period is set to “month” or “year”. What I want to do is is use these variables to calculate x months from now.

I’ve seen the 1.month.from_now and 1.year.from_now but what I need is something like:

eval("#{frequency}.#{period.downcase}.from_now")

but I’m not sure about the use of eval as I’m new to Rails/Ruby and in PHP the use of eval usually means you’re doing something wrong.

Is eval evil in Rails?

Answer 1

eval is pretty slow. You can use Object#send:

irb(main):003:0> frequency = 1
irb(main):004:0> period = "month"
irb(main):005:0> frequency.send(period).from_now
=> Mon, 30 May 2011 16:57:12 UTC +00:00

And you can read about the speed here.