insightful method missing snippets... eg going into ActiveRecord machinery to understand "magical" find_by_whatever methods

method_missing.rb

 class ActiveRecord::Base
      def method_missing(meth, *args, &block)
        if meth.to_s =~ /^find_by_(.+)$/
          run_find_by_method($1, *args, &block)
        else
          super # You *must* call super if you don't handle the
                # method, otherwise you'll mess up Ruby's method
                # lookup.
        end
      end

      def run_find_by_method(attrs, *args, &block)
        # Make an array of attribute names
        attrs = attrs.split('_and_')

        # #transpose will zip the two arrays together like so:
        #   [[:a, :b, :c], [1, 2, 3]].transpose
        #   # => [[:a, 1], [:b, 2], [:c, 3]]
        attrs_with_args = [attrs, args].transpose

        # Hash[] will take the passed associative array and turn it
        # into a hash like so:
        #   Hash[[[:a, 2], [:b, 4]]] # => { :a => 2, :b => 4 }
        conditions = Hash[attrs_with_args]

        # #where and #all are new AREL goodness that will find all
        # records matching our conditions
        where(conditions).all
      end
    end
    
class Dummy  
  def method_missing(m, *args, &block)  
    puts "There's no method called #{m} here -- please try again."  
  end  
end  

Dummy.new.anything

class Numeric
   
   def method_missing( method_id, *args, &block)
     if method_id.to_s == "milles"
       self * 1000
     else
       super
     end
   end
 
 end