class ActionDispatch::Routing::Mapper

root to: 'dashboard#show'

end
end
root to: 'devise/registrations#new'
as :user do
unauthenticated do

You can optionally specify which scope.
Allow you to route based on whether a scope is *not* authenticated.

def unauthenticated(scope = nil)
  constraint = lambda do |request|
    not request.env["warden"].authenticate? scope: scope
  end
  constraints(constraint) do
    yield
  end
end