ruby_classes.rb

class Computer
  $manufacturer = "Mango Computer, Inc."
  @@files = {hello: "Hello, world!"}
  
  def initialize(username, password)
    @username = username
    @password = password
  end
  
  def current_user
    @username
  end
  
  def self.display_files
    @@files
  end
end

# Make a new Computer instance:
hal = Computer.new("Dave", 12345)

puts "Current user: #{hal.current_user}"
# @username belongs to the hal instance.

puts "Manufacturer: #{$manufacturer}"
# $manufacturer is global! We can get it directly.

puts "Files: #{Computer.display_files}"
# @@files belongs to the Computer class.
################
class MyClass
  $my_variable = "Hello!"
end

puts $my_variable
###########
class Person
  # Set your class variable to 0 on line 3
  @@people_count = 0
  
  def initialize(name)
    @name = name
    # Increment your class variable on line 8
    @@people_count += 1
  end
  
  def self.number_of_instances
    # Return your class variable on line 13
    @@people_count
  end
end

matz = Person.new("Yukihiro")
dhh = Person.new("David")

puts "Number of Person instances: #{Person.number_of_instances}"
#################
class ApplicationError
  def display_error
    puts "Error! Error!"
  end
end

class SuperBadError < ApplicationError
end

err = SuperBadError.new
err.display_error
###############
class Creature
  def initialize(name)
    @name = name
  end
  
  def fight
    return "Punch to the chops!"
  end
end

# Add your code below!
class Dragon < Creature
    def fight
       return "Breathes fire!" 
    end
end
########################
class Creature
  def initialize(name)
    @name = name
  end
  
  def fight
    return "Punch to the chops!"
  end
end

# Add your code below!
class Dragon < Creature
    def fight
       puts "Instead of breathing fire..."
       super
    end
end

d = Dragon.new("dragiii")
d.fight
############
class Message
    @@messages_sent = 0
    
   def initialize(from, to)
      @from = from 
      @to = to
      @@messages_sent += 1
   end
end

class Email < Message
   def initialize(from, to)
      super
   end
end

my_message = Message.new("me", "her")
################
class Computer
    @@users = {}
   def initialize(username, password)
       @username = username
       @password = password
       @files = {}
       @@users[username] = password
   end
   
   def create(filename)
      time = Time.now
      @files[filename] = time
      puts "New file created: #{filename} - #{time} - #{@username}"
   end
   
   def update(filename)
       time = Time.now
       @files[filename] = time if @files[filename]
       puts "File #{filename} updated!" 
   end
   
   def Computer.get_users
      @@users 
   end
end

my_computer = Computer.new("john", "1234")
my_computer.create("new_file.pdf")
puts Computer.get_users
sleep(4)
my_computer.update("new_file.pdf")
puts Computer.get_users
my_computer