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Setting The Default Page


    Now that the structure is complete, let's make the flow work smoothly.

    Currently when you go to http://localhost:3000 you see the "Yay! You’re on Rails!" message.

    It would be easier to use our app if http://localhost:3000 went directly to the topics list.

    In this step we'll make that happen and learn a bit about routes in Rails.


Step 1: Add a root route

Open the file config/routes.rb in an editor.

Search the file for the line resources :topics. It will be near the top.

Right above that line, add a new line: root 'topics#index'. When you are done the file should look like this:

Rails.application.routes.draw do
  root 'topics#index'
  resources :topics
  # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html

Step 2: Remove the comment (optional)

Near the bottom, there is a line that starts with a #. This is called a comment. It is ignored by ruby and is used for reference or further explanation of nearby code. If you want, you can remove it, or keep it there to look at later. It's totally up to you!

Step 3: Confirm your changes

Go back to http://localhost:3000/. You should be taken to the topics list automatically.

For Cloud9: delete any text after 'amazonaws.com', or click to preview running application in the editor again


  • root 'topics#index' is a Rails route that says the default address for your site is topics#index. topics#index is the topics list page (the topics controller with the index action).
  • Rails routes control how URLs (web addresses) get matched with code on the server. Similar to how addresses match with houses and apartments.
  • The file config/routes.rb is like an address directory listing the possible addresses and which code goes with each one.
  • routes.rb uses some shortcuts so it doesn't always show all the possible URLs. To explore the URLs in more detail we can use the terminal.

At the terminal type rails routes. You should get something that looks like this:

$ rails routes

    Prefix Verb   URI Pattern                Controller#Action
      root GET    /                          topics#index
    topics GET    /topics(.:format)          topics#index
           POST   /topics(.:format)          topics#create
 new_topic GET    /topics/new(.:format)      topics#new
edit_topic GET    /topics/:id/edit(.:format) topics#edit
     topic GET    /topics/:id(.:format)      topics#show
           PATCH  /topics/:id(.:format)      topics#update
           PUT    /topics/:id(.:format)      topics#update
           DELETE /topics/:id(.:format)      topics#destroy

This shows all the URLs your application responds to. The code that starts with colons are variables so :id means the id number of the record. The code in parentheses is optional.

You can also get this information on your site in development. Go to http://localhost:3000/rails/info/routes

For Cloud9:

Navigate to https://<your-preview-url>.amazonaws.com/rails/info/routes

Step 4: Exploring Routes (optional)

Now you can have a look at the paths that are available in your app. Let's try looking at one of the topics routes we just generated. Open up your rails console and play:

$ rails console
> app.topics_path
=> "/topics"
> app.topics_url
=> "http://www.example.com/topics"

app is a special object that represents your entire application. You can ask it about its routes (as we just did), play with its database connections, or make pseudo-web requests against it with get or post (and lots more).

Next Step:

Back to CRUD With Scaffolding