Avoiding Demeter violations in Rails

demeter.rb

class Example < ActiveRecord::Base

  # The rest of the class .....


  def get_object_and_method method_name
    assoc_methods = [
      :push,
      :concat,
      :build,
      :create,
      :create!,
      :size,
      :length,
      :count,
      :sum,
      :empty?,
      :clear,
      :delete,
      :delete_all,
      :destroy_all,
      :find,
      :find_first,
      :exists?,
      :uniq,
      :reset
    ]

    method_string = method_name.to_s

    #Iterate over association method names
    assoc_methods.map(&:to_s).each do |assoc_method|
      #if the missing method starts with the association method
      if method_string.starts_with? assoc_method
        assoc = method_string.sub(assoc_method, '').sub('_', '')
        #and this object responds to the name of the remainder
        #of the string or its pluralized form
        if self.respond_to? assoc
          #then return the object and method names
          return [assoc, assoc_method]
        elsif self.respond_to? assoc.pluralize
          return [assoc.pluralize, assoc_method]
        end
      end
    end
    [nil, nil]
  end

  def method_missing method_name, *args, &block
    other_object, other_method = get_object_and_method(method_name)

    #if a valid object and method name was derived
    if other_object && other_method
      #then delegate
      send(other_object).send(other_method, *args, &block)
    else
      super
    end
  end

  def respond_to? method_name, include_private=false
    other_object, other_method = get_object_and_method(method_name)
    if other_object && other_method
      true
    else
      super
    end
  end
end

I had to move the call to super to the end of respond_to? because super may call a callback - seemed safer to leave it at the end (if a bit less efficient).

Description: Convert calls of the form model.association.find to model.find_association.