Ruby 1.8: SimpleDelegator is very slow

If you're still working on ruby 1.8, you should know that using SimpleDelegator is often prohibitively slow. I have seen SimpleDelegator.new(myActiveRecordModel) take 50ms+ per instantiation.

The reason is that SimpleDelegator actually loops through all methods of an object and does a define_method. Which is not exactly fast.

To speed up your code, you can often simply replace

class MyUserDecorator < SimpleDelegator
   ...
end

with

class MyUserDecorator < DelegateClass(User)
   ...
end

This will obviously not work if you pass in anything else than a user object, and hence you can no longer easily chain delegators.