controller_example.rb

# songs_controller.rb
class SongsController < ApplicationController
  def index
    @songs = Song.all
  end

  def show
    @song = Song.find(param[:id])
  end

  def create
    Song.create(params[:song])
  end
end

# application_controller.rb
class ApplicationController < ActionController::Base
end

# routes.rb
Rails.application.routes.draw do
  resources :songs, only: [:index, :show, :create]
end