FAQ: Virtual Computer - Who are the Users?

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This community-built FAQ covers the “Who are the Users?” exercise from the lesson “Virtual Computer”.

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[dcts]

I think the users variable should not be a hash, since it cannot store users with identical names. So when storing two users with the same name the old one gets overwritten. See code below:

class Computer
  @@users = {}  # Hash, not a good choice
  
  def initialize(username, password)
    @username = username
    @password = password
    @files = {}
    @@users[username] = password
	end
  
  def Computer.leak_all_users_and_passwords
    @@users.each {|k,v| puts "User #{k} has password #{v}"}
  end
end

my_computer = Computer.new("thomas", 1234)
ben_computer = Computer.new("Ben", 13415)
thomas_computer = Computer.new("thomas", 247686)
Computer.leak_all_users_and_passwords
# where did the first user go?

EDIT: I fixed the problem by creating a new class “users”, and then creating an array of users as classvariable in computer class. Now each time a new instance of computer is generated also a new user is generated and pushed to the classarray which holds all user objects. Maybe someone finds that helpful or has any feedback/improvements?

class User
  def initialize(username, password)
    @username = username
    @password = password
  end
  def show_personal_data
    puts "username: #{@username}, password: #{@password}"
  end
end


class Computer
  @@users = []  # array instead of hash to prevent overriding duplicate users

  def initialize(username, password)
    @username = username
    @password = password
    @@users << User.new(username, password)
	end

  def Computer.leak_all_passwords
    @@users.each { |user| user.show_personal_data }
  end
end

my_computer = Computer.new("thomas", 1234)
his_computer = Computer.new("Ben", 13415)
another_thomas_computer = Computer.new("thomas", 247686)
Computer.leak_all_passwords  # now all three users are displayed!

[dev9785014746]

I’m a bit confused on why we have to “grab” or return @@users from a class-specific method.

In other words, why does @@users = Hash.new require Computer.get_users() (below)?

def Computer.get_users
    return @@users
end

[design4366914386]

Hi everyone!

Is it just me or is the explanation of class methods very poor?

There is no mention that class methods need to begin with a capital letter, but I assume the must because that’s what they have written in the example?

It says class methods are different to instance methods, but there is no real explanation of the differences other than the fact that instance methods work on particular objects. What makes them work that way? Is it simply because we write an instance method using lower case letters and class methods with a capital letter?

I’d be very grateful if someone could elaborate on this.

Thanks.