Todo module in Ruby; MVC

todo.rb

module Todo
  require 'json'

  class Controller
    def initialize
      @list = List.new
    end

    def run(args)
      @list.read_input(args)
    end
  end

  class List
    def read_input(args)
      command_arg = args[0]
      property_arg = args.drop(1).join(" ")
      file_name = './todo.json'
      task_array = read_file(file_name)

      case command_arg
      when "add"
        tasks = add_task(task_array, property_arg)
      when "display"
        Viewer.render_display_tasks(task_array)
      when "delete"
        tasks = delete(task_array, property_arg)
      when "complete"
        tasks = complete(task_array, property_arg)
      else
        Viewer.render_input_error
      end
      write_file(task_array, file_name)
    end

    private
    def read_file(file_name)
      file_str = File.open(file_name, 'r').read
      hashes = JSON.parse(file_str)
      hashes_to_tasks(hashes)
    end

    def write_file(task_array, file_name)
      my_hash = tasks_to_hashes(task_array)
      hash_str = JSON.generate(my_hash)
      File.open(file_name, 'w').write(hash_str)
    end

    def hashes_to_tasks(hashes) # read_file
      task_obj_array = []
      hashes.each_pair do |key, value|
        message = ""
        deleted = false
        completed = false
        value.each_pair do |sub_key, sub_value| #every task
          message = sub_value if sub_key == "message"
          deleted = sub_value if sub_key == "deleted"
          completed = sub_value if sub_key == "completed"
        end
        task_obj_array << Task.new(key, deleted, message, completed)
      end
      task_obj_array
    end

    def tasks_to_hashes(task_array) # write_file
      temp_hash = {}
      task_array.each do |task|
        temp_hash.merge!({ task.name => { "deleted" => task.deleted, "message" => task.message, "completed" => task.completed } })
      end
      temp_hash
    end

    def add_task(task_array, property_arg)
      task_array << Task.new("task#{task_array.length+1}", false, property_arg, false)
      task_array
    end

    def complete(task_array, task_index)
      task_array[task_index.to_i - 1].set_completed(true)
      task_array
    end

    def delete(task_array, task_index)
      task_array[task_index.to_i - 1].set_deleted(true)
      task_array
    end
  end

  class Task
    attr_reader :name, :deleted, :message, :completed

    def initialize(name, deleted, message, completed)
      @name = name
      @deleted = deleted
      @message = message
      @completed = completed
    end

    def set_deleted(bool)
      @deleted = bool
    end

    def set_completed(bool)
      @completed = bool
    end
  end

  class Viewer
    class << self
      def render_display_tasks(task_array)
        puts "-" * 60
        puts "Here are the tasks that are on your list: "
        task_array.each do |task|
          puts "[#{task.completed ? "X" : " "}] #{task.name}: #{task.message}" if task.deleted == false
        end
        puts "-" * 60
      end

      def render_input_error
        puts "There was an error with the command."
      end
    end
  end
end

todo_app = Todo::Controller.new
todo_app.run(ARGV)