Rails Routing Constraints

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title: “Constraints de roteamento no Rails” date: 2021-04-05 09:00:20 +0300 categories: rails routing tags: rails routing constraints —-

Quando usar routing constraints no Rails

Constraints permitem ao roteador decidir para onde enviar a request sem empurrar a lógica para controllers. Útil para roteamento por subdomínio, home diferente para guest/logado, controle de formato e proxys.

Abordagem base (controller)

Você pode redirecionar no controller, mas o router continua fazendo trabalho extra:

# app/controllers/home_controller.rb
class HomeController < ApplicationController
  before_action :redirect_to_dashboard_if_signed_in

  def index; end

  private

  def redirect_to_dashboard_if_signed_in
    redirect_to dashboard_path if signed_in?
  end
end

# config/routes.rb
Rails.application.routes.draw do
  resource :dashboard, only: [:index]
  resource :home, only: [:index]
end

Use routing constraints

Mantenha decisões em routes.rb. Padrões comuns:

1. Constraint por segmento

   match '/:year/:month/:day' => 'info#about',
     constraints: { year: /\d{4}/, month: /\d{2}/, day: /\d{2}/ }
   

2. Constraint por request (User-Agent, subdomínio, formato)

   match '/:year/:month/:day' => 'info#about',
     constraints: { user_agent: /Firefox/ }
   

3. Constraint dinâmica (lambda ou classe)
   • Lambda:

     get '*path', to: 'proxy#index',
     constraints: ->(req) { req.env['SERVER_NAME'].match?('foo.bar') }
     

   • Class: ```ruby constraints Subdomain do get ‘*path’, to: ‘proxy#index’ end

class Subdomain def self.matches?(request) request.subdomain.present? && request.subdomain.start_with?(‘foobar’) end end

### Exemplo: home para guest vs logado

```ruby
# lib/signed_in_home.rb
class SignedInHome
  def self.matches?(request)
    request.cookies['remember_token'].present?
  end
end

# config/routes.rb
Rails.application.routes.draw do
  constraints SignedInHome do
    root to: 'dashboard#show', as: :dashboard
  end

  root to: 'home#show'
end

Aqui o router decide qual root servir antes de chegar ao controller. Troque a lógica do cookie pelo seu mecanismo de auth (ex.: Warden, JWT etc.).

Nota: há 2 rotas para root, uma dentro do constraint e outra fora. A ordem importa.

Referências

• Thoughbot Clearance gem e Clearance::Constraints::SignedIn.
• Documentação do Rails sobre Routing.