router.rb

class ItemsController

  def initialize
    @items = []
    1.upto(10) do |i|
      @items << { id: i, name: "Item #{i}" }
    end

    # => GET /items
    def index
      @items.each do |item|
        puts "id: #{item[:id]} - #{item[:name]}"
      end
    end

    # => POST /items
    def create

    end

    # => GET /items/:id
    def show(index)
      item = @items[index - 1]
      puts "id: #{item[:id]} - #{item[:name]}"
    end

    # => DELETE /items/:id
    def destroy

    end

    # => PUT /items/:id
    def update

    end
  end

end

class Router

  def initialize(url)

    items = ItemsController.new
    case url
    when '/items'
      items.index
    when '/items/1'
      items.show(1)
    when '/items/2'
      items.show(2)
    else
      items.index
    end
  end
end

http_method = ARGV[0]
url = ARGV[1]

Router.new(http_method, url)