Passing variables/parameters from one Ruby class to a loaded Ruby program - ruby

Question

The below combined programs should ask for a number remove the first digit (lets call this new number x) and then compute x % 7. Ex: (1121546 % 7) = 5
This all appears to be working except that the number entered in will always compute to 0. modulo_7.rb works by itself and will print the correct outcome when passed a parameter.
The question is am I not passing the variables/ parameters properly or is there something else that is getting in the way?
class Number_check_interface
def get_cert_number
print "You are about to check receive the check number for a policy/cert id."
#cert_id = nil
until #cert_id.is_a?(Fixnum) do
puts " Enter the policy/cert ID. "
begin
#cert_id = Integer(gets)
rescue ArgumentError
end
end
end
end
class Run_number_check_interface
def run
load 'modulo_7.rb'
n = Number_check_interface.new
n.get_cert_number
checking_policy_number = Get_policy_check_digit.new(#cert_id)
checking_policy_number.create_check_digit
end
end
run = Run_number_check_interface.new
run.run
modulo_7.rb
This program removes the first digit (index 0) of a 7 digit number and returns the difference 7%18 is 4 since 4 is remainder of how many times 7 can fit into 18.
class Get_policy_check_digit
def initialize(cert_id)
#instance variable
#cert = cert_id
end
def create_check_digit
cert_id_6 = #cert.to_s
cert_id_6.slice!(0)
puts cert_id_6
check_digit = cert_id_6.to_i % 7
puts "Your check digit is #{check_digit}"
end
end
# n = Get_policy_check_digit.new(1121546) When uncommented this will create a new instance
# of Get_policy_check_digit with the parameter 1121546
# n.create_check_digit This will run the method create_check_digit with the
# parameter 1121546

Answer 1

Instance variables are scoped to an individual instance of a class. So when you say #cert_id = Integer(gets) inside Number_check_interface, you are only setting #cert_id for that particular instance of Number_check_interface. Then, when you later write Get_policy_check_digit.new(#cert_id) inside Run_number_check_interface, you are referring to an entirely different #cert_id, one which is specific to that particular instance of Run_number_check_interface, and not to the Number_check_interface you stored in n earlier.
The simple solution is to return #cert_id from Number_check_interface#get_cert_number, and then pass the returned value to Get_policy_check_digit.new:
class Number_check_interface
def get_cert_number
print "You are about to check receive the check number for a policy/cert id."
#cert_id = nil # This is an instance variable. It's only accessible
# from inside this instance of `Number_check_interface`
until #cert_id.is_a?(Fixnum) do
puts " Enter the policy/cert ID. "
begin
#cert_id = Integer(gets)
rescue ArgumentError
end
end
return #cert_id # Return the contents of #cert_id
end
end
class Run_number_check_interface
def run
load 'modulo_7.rb'
n = Number_check_interface.new
cert_number = n.get_cert_number # Here we call `get_cert_number` and
# set `cert_number` to it's return
# value.
# Notice how we use `cert_number` here:
checking_policy_number = Get_policy_check_digit.new(cert_number)
checking_policy_number.create_check_digit
end
end
Other tips:
Convention in Ruby is to name classes with CamelCase.
Require dependencies at the top of your files, not in the middle of method calls.
Unless you have a very good reason not to, use require, not load
You might want to think a bit harder about what purpose these classes serve, and what behavior they are intending to encapsulate. The API seems a bit awkward to me right now. Remember, tell, don't ask.

Answer 2

Why are these separate classes? The design here seems strange, is this ported from another language? It's more complicated than it needs to be. Without changing your structure, here's what's wrong:
In Run_number_check_interface you are reading #cert_id, it doesn't have an instance variable named that, but Number_check_interface does. Just return it from get_cert_number:
class Number_check_interface
def get_cert_number
print "You are about to check receive the check number for a policy/cert id."
cert_id = nil
until cert_id.is_a?(Fixnum) do
puts " Enter the policy/cert ID. "
begin
cert_id = Integer(gets)
rescue ArgumentError
end
end
cert_id # <-- returing the value here
end
end
class Run_number_check_interface
def run
load 'modulo_7.rb'
n = Number_check_interface.new
cert_id = n.get_cert_number # <-- saving here
checking_policy_number = Get_policy_check_digit.new(cert_id) # <-- no longer an ivar
checking_policy_number.create_check_digit
end
end
run = Run_number_check_interface.new
run.run