Constraints

#lib/startup_constraint.rb
class StartupConstraint
  def matches?(request)
    id = request.path.gsub("/", "")
    Startup.find_by_slug(id)
  end
end

#lib/user_constraint.rb
class UserConstraint
  def matches?(request)
    id = request.path.gsub("/", "")
    User.find_by_slug(id)
  end
end

Routes

  resources :startups

  resources :users

  # The priority is based upon order of creation: first created -> highest priority.
  # See how all your routes lay out with "rake routes".

  # You can have the root of your site routed with "root"
  root 'pages#home'

  constraints(Constrainer::UserConstraint.new) do
    get '/:id', to: "users#show", as: 'short_user'
  end

  constraints(Constrainer::StartupConstraint.new) do
    get '/:id', to: "startups#show", as: 'short_startup'
  end