Rails Views and Layouts

Sinatra Vs Rails

With Sinatra, we've seen that if there is a file called layout.erb, this file will be used as the app layout by default.

If this file layout.erb contains a yield statement <%= yield %>, then the template rendered for the current route will be "injected" where the yield statement is in the layout. Combined, the templates and layouts will be sent back to the client.

This logic is pretty much the same with Ruby on Rails. When the app is created, Rails will automatically add a layout application.html.erb in app/views/layouts/application.html.erb. This layout already contain a yield statement and all the links to css and js files in the head part of the html document.

Rails Views

In Rails, the logic for the rendering a view is quite straightforward. Given that every route in Rails will execute a method inside a controller, when the method is executed, Rails will look for:

1. A folder inside view corresponding to the controller's name (folder post for PostController).
2. A file inside that folder corresponding to an action in that controller (file index.html.erb).

For example , if we call http://localhost:3000/posts, Rails will execute the method index in the controller posts and then, look for a view located in app/views/posts/index.html.erb This works when the method always renders the same view.

In some cases though, you may want to render a view with a different name than the current method. For example: if a post was saved successfully go to the index page, otherwise go back to the form. To show a different view than the default view, you would render a different view in a controller's action.

There are different syntaxes for render, and they all do the same thing.

    render :switch
    render action: :switch
    render "switch"
    render "switch.html.erb"
    render action: "switch"
    render action: "switch.html.erb"
    render "home/switch"
    render "home/switch.html.erb"
    render template: "home/switch"
    render template: "home/switch.html.erb"
    render "/path/to/rails/app/views/home/switch"
    render "/path/to/rails/app/views/home/switch.html.erb"
    render file: "/path/to/rails/app/views/home/switch"
    render file: "/path/to/rails/app/views/home/switch.html.erb"

Rails Layouts

By default, Rails will render the layout application.html.erb - just like layout.html.erb in Sinatra - but sometimes, you want to render a template in a different layout.

You can render a differnt layout by doing the following:

render layout: "name_of_layout"

This line will just tell Rails to use the same logic of template rendering, but instead of using the default application.html.erb, it will render the template inside name_of_layout.html.erb.

You can also do render layout: false if you wanted to use ajax to pull in a view.