Performance Impact of Generating 100's of Dynamic Methods in Ruby?

Question

What are the performance issues associated with generating 100's of dynamic methods in Ruby?

I've been interested in using the Ruby Preferences Gem and noticed that it generates a bunch of helper methods for each preference you set.

For instance:

class User < ActiveRecord::Base
  preference :hot_salsa
end

...generates something like:

user.prefers_hot_salsa?         # => false
user.prefers_hot_salsa          # => false

If there are 100's of preferences like this, how does this impact the application? I assume it's not really a big deal but I'm just wondering, theoretically.

Answer 1

Almost every Ruby program does this sort of thing like crazy — this is what the standard attr_ family of methods do, which are used with impunity in pretty much every Ruby program ever. Many programs also do this in other places — it's incredibly common with method_missing hacks, for instance. I've never timed to see exactly how it performs, but it's common enough that if it were a significant problem, it should have been noticed by now.