{_{_{_{ <| <| <| M - A - Y - T - S - C - H - I - D - Z - E - H |> |> |> }_}_}_}

# app/controllers/
# -> application_controller.rb
# app/views/
# -> layouts/
#    -> application.html.erb : Default template of the app
#     <%= yield %>

# controller: - a + b
# view: a + b = ?

# $ rails server
# $ rails generate controller <name>
# $ rails generate controller calculator


# app/controllers/
# -> calculator_controller.rb

class CalculatorController < ApplicationController
  def index  # <-- action
    # ...
  end
end

# app/views/
# -> calculator/
#    -> <action_name>.html.erb

# app/views/calculator/index.html.erb
# <h1>GEI</h1>

# /upload -> action
# home -> another action


# config/routes.rb

Rails.application.routes.draw do
  get 'calculator' => 'calculator#index'
end

# -------------------------------------------------------

# /calculator?a=3&b=12

# app/controllers/calculator_controller.rb

class CalculatorController < ApplicationController
  def index
    a = params[:a].to_i
    b = params[:b].to_i

    @result = a + b  # @ means instance variable (automatically accessible in the view)
  end
end

# app/views/calculator/index.html.erb

<h1>
  <%= @result %>
</h1>