todo_list.rb

require 'observer'

# my attempt at the Observer Pattern based on:
# http://docs.ruby-lang.org/en/2.2.0/Observable.html
# ... and plenty of struggling
​
class TodoList
  include Observable
​
  attr_reader :title, :items
  attr_accessor :todo_file
​
  # Initialize todo list with a title and no items
  def initialize(list_title)
    @title = list_title
    @items = []
    add_observer(Watcher.new) # initialize Watcher class for Observer Pattern
  end
​
  # class methods for setting up file, writing to file, reading from file
  def self.setup_file
    @todo_file = File.new('program.txt', 'w+')
  end
​
  def self.write_to_file(text, file = @todo_file)
    open(file, 'w+') { |f| f.puts text }
  end
​
  def self.read_from_file(file = @todo_file)
    open(file, 'r') { |f| puts f.read }
  end
​
  def print_divider(length)
    puts '-' * length
  end
​
  def print_todo
    puts
    puts
    puts '%30s' % @title
    print_divider 50
    Item.print_items(@items)
  end
​
  # Creates a new Item and adds it to the array of Items
  def add_item(new_item)
    item = Item.new(new_item)
    @items.push(item)
    # notify Watcher of changes
    changed
    notify_observers(self, new_item)
  end
​
  # delete by number - get item by number, subtract one
  # to get the correct array index
  def delete_item(item_number)
    @items.delete_at(item_number - 1) unless item_number == 0
    # notify Watcher of changes
    changed
    notify_observers(self, item_number)
  end
​
  # get item by number, subtract one for correct array index
  def get_item(item_number)
    @items[(item_number - 1)]
  end
​
  # delete all items by resetting array to empty
  def delete_all_items
    @items = []
  end
​
  def update_title(title)
    @title = title
    # notify Watcher of changes
    changed
    notify_observers(self, title)
  end
​
  def make_time_stamp
    Time.now.strftime('%m/%d/%Y')
  end
​
  def to_s
    @title.to_s
  end
end
​
class Item
  include Observable
​
  attr_reader :description, :completed_status
​
  # Initialize item with a description and marked as not complete
  def initialize(item_description)
    @description = item_description
    @completed_status = false
  end
​
  def mark_complete
    @completed_status = true
    # notify Watcher of changes
    changed
    notify_observers(self, completed_status) # not sure about second parameter
  end
​
  def completed?
    @completed_status
  end
​
  def self.print_items(items)
    items.each { |item| puts item }
  end
​
  def to_s
    '%-25s Completed: %s' % [@description, completed?]
  end
end
​
# class for using the Observer Pattern. (module Observable)
# write the Todo List to file every time that TodoList data changes
# ^ silently
class Watcher
  def update(todolist, changed_data)
    # write todolist to program.txt
    TodoList.write_to_file(todolist.print_todo)
  end
end