gistfile1.rb

LOOKUP_CHAIN = [:params, :user, :session, :http, :default]

def self.set_by(inputs)
  locale = nil
  LOOKUP_CHAIN.each do |lookup|
    locale = send("by_#{lookup}", inputs[lookup])
    break if locale
  end
  return locale
end

Thought about this the other day but just got around to trying it this afternoon. I believe #any? stops when it reaches a truthy result, so how about this:

def self.set_by(inputs)
  locale = nil
  LOOKUP_CHAIN.any? { |lookup| locale = send("by_#{lookup}", inputs[lookup]) }
  return locale
end

Passes the test harness.