In Rails, routes map an incoming URL to a controller action. When you define a route for your application, you also get path and URL helpers to build relative or absolute URLs from the route's name. For example, suppose that you have a users resource in your config/routes.rb:

resources :posts

This route creates the method posts_path that you can use in the view. For simple routes, you can probably guess the output of the helper, e.g., the posts_path helper will return the URL /posts. For complex routes, especially nested ones, it can be hard to figure out the URL until you use the helper to render the view.

This post shows a simple way to check the output of URL and path helpers directly from the Rails console. We will also see how to access these helpers in your models.

Here's a typical route file with a single route.

# routes.rb

Rails.application.routes.draw do

  get '/posts/:id/preview', to: 'posts#preview', as: "preview_post"

end

This route maps the URL posts/:id/preview to PostsController#preview action. Additionally, we have named the route preview_post using the as option. Hence, Rails will automatically generate preview_post_path and preview_post_url helpers for us.

To see the routes in your application, you can run the rails routes command.

> bin/rails routes -g preview

Prefix Verb URI     Pattern                  Controller#Action
preview_post GET  /posts/:id/preview(.:format) posts#preview

However, this doesn't tell you what URL the route will generate for you. For that, you can call the helper methods on the app object, which represents your application. Rails adds all the helpers to the app object when it boots. Hence you can check the output of any named route helper in the console, which is pretty handy during development.

irb(main):018:0> post = Post.first

irb(main):019:0> app.preview_post_path(post)
=> "/posts/5/preview"

Accessing Helpers from Models

By default, the helper methods are accessible from your controllers, views, and mailers. If you need to access the auto-generated helper methods from other places (such as a model), then you can do that by including Rails.application.routes.url_helpers in your class:

class Post < ActiveRecord::Base
  include Rails.application.routes.url_helpers

  def link
    post_path(self)
  end
end

Post.find(1).link # => "/posts/1"

I hope that helps.