Specifying a layout file for devise gem in rails (what does this do?)

I know how to specify a layout file for devise. But what I don't understand is how this works. Specifically, in the code below my layout_name_for_devise is used if it's a devise controller. So then I figured 开发者_如何学编程this must mean the "application" layout would be used if it's NOT a devise controller (which in my case is in app/views/layouts/application.html.haml). Now, I have other layouts, for example one called home. I thought my views using my home layout would break...but it turns out it work fine. I don't understand how this works. For example, when the code below runs, how is it that my app/views/layouts/home.html.haml layout still gets called correctly?

class ApplicationController < ActionController::Base
  layout :layout_by_resource

  protected

  def layout_by_resource
    if devise_controller?
      "layout_name_for_devise"
    else
      "application"
    end
  end

---

A good nights rest does wonders for the brain. So I woke up understanding how this works...but also feeling silly for not seeing it earlier.

tl;dr - this code is inside the application controller. Other controllers don't call this code. That's why it works correctly.

Longer Answer:

Rails tries to find layouts based on the controller name. If a layout doesn't exist then rails will use the application layout.

So in my Home controller rails first looks for a home layout. Since there is one it uses that layout.

I'm not sure what devise does but it's not looking for a layout named devise so instead it uses application layout. And that's when the code above runs. Since the controller is a devise controller the layout then gets changed to "layout_name_for_devise".