Rails 4's resource parameter name option for Rails 3

action_dispatch_routing_mapper_resources_resource_param.rb

# From https://stackoverflow.com/questions/6592038/change-the-name-of-the-id-parameter-in-routing-resources-for-rails3/13427336#13427336
#
# Unfortuantely, in Rails 3, the :key option for resources was
# removed, so you can no longer easily change the name for routes
# created in this way by just passing in an extra option.
#
# All is not lost, however; it seems in Rails 4, the :param option
# has been added, which seems to do exactly what you're looking for.
# You can take a look at the Rails 3 code compared to the Rails 4
# code.
#
# Rails 3: https://github.com/rails/rails/blob/e359e3ab935d6790d9a1181e6ebe0038ad168b94/actionpack/lib/action_dispatch/routing/mapper.rb#L867
#
# Rails 4: https://github.com/rails/rails/blob/e2334a249aa7b9e18d684fd5cf213e78053a9222/actionpack/lib/action_dispatch/routing/mapper.rb#L1020
#
# This patch backports the :param option.
#
class ActionDispatch::Routing::Mapper::Resources::Resource
  # overridden:

  def member_scope
    "#{path}/:#{param}"
  end

  def nested_scope
    "#{path}/:#{nested_param}"
  end

  # backported:

  def param
    @param ||= (@options[:param] || :id).to_sym
  end

  def nested_param
    :"#{singular}_#{param}"
  end
end

I had to add :param to ActionDispatch::Routing::Mapper::Resources::RESOURCE_OPTIONS to get this patch to work: https://github.com/rails/rails/blob/e359e3ab935d6790d9a1181e6ebe0038ad168b94/actionpack/lib/action_dispatch/routing/mapper.rb#L861

Not the cleanest option but a quick fix:

module ActionDispatch::Routing::Mapper::Resources
  RESOURCE_OPTIONS  = [:as, :controller, :path, :only, :except, :param]
end