routes.rb

class ShopRoutesConstraint
  def self.matches?(request)
    ! ADMIN_DOMAIN_NAMES.include?(request.host)
  end
end

class AdminRoutesConstraint
  def self.matches?(request)
    ADMIN_DOMAIN_NAMES.include?(request.host)
  end
end

Takeaway::Application.routes.draw do

  constraints(AdminRoutesConstraint) do
    devise_for :shop_admins
  end

  constraints(ShopRoutesConstraint) do
    devise_for :clients
  end
end