Ruby- saving user input

Question

I am writing a course management program in Ruby to allow a user to to add/ remove modules to a scheme.

Currently, my program will allow the user to add modules, but when I then try to remove them, I am told that they don't exist.

The method I'm using to add the modules is:

def self.add_module
# schemes = {}
 scheme_exists = false
 add_another_scheme = true
# module_exists = false
 add_another_module = true

 while add_another_scheme
   print "Enter scheme name: "
   scheme_name = gets
   $schemes.has_key?(scheme_name.chop) ? scheme_exists = true : scheme_exists = false

   if !scheme_exists
     $schemes[scheme_name.chop] = []
     puts "Scheme #{scheme_name.chop} has been added to the system"
   elsif
     scheme_exists = true
     puts "This scheme has already been added"
   end

   while add_another_module
     print "Enter module name: "
     module_name = gets
     $schemes[scheme_name.chop].include?(module_name.chop) ? true : $schemes[scheme_name.chop] << module_name.chop
    # puts "Module #{module_name.chop} has been added to #{scheme_name.chop}"

     # 22/08/2012 at 14:15 Now need to read in each module's unique identifier and year it belongs to
     print "Enter module ID: "
     $module_ID =gets
     $schemes[scheme_name.chop].include?($module_ID.chop) ? true : $schemes[scheme_name.chop] << $module_ID.chop
     $schemes.has_key?($module_ID.chop) ? module_exists = true : module_exists = false

     print "Enter the academic year to which the module belongs: "
     module_year = gets
     $schemes[scheme_name.chop].include?(module_year.chop) ? true : $schemes[scheme_name.chop] << module_year.chop

     if !$module_exists
       $schemes[$module_ID.chop] = []
       puts "Module #{$module_ID.chop} : #{module_name.chop} has been added to #{scheme_name.chop} for the year #{module_year}"
     elsif
       $module_exists = true
       puts "A module with this ID has already been added to the scheme, please check if the module already exists, or choose another ID "
     else
     #  puts "Module #{module_name.chop}, #{module_ID.chop} has been added to #{scheme_name.chop} for the year #{module_year}"
     end

    # puts "Module #{module_name.chop}, #{module_ID.chop} has been added to #{scheme_name.chop}"

     print "Add another module? "
     ask_if_user_wants_to_add_another_module = gets
     if(ask_if_user_wants_to_add_another_module.chop == "y" or ask_if_user_wants_to_add_another_module == "yes")
      add_another_scheme = false
     else if(ask_if_user_wants_to_add_another_module.chop != "y" or ask_if_user_wants_to_add_another_module != "yes")
       Application.main_menu
          end
   end

 end

and the method I'm using to try to remove the module is:

def self.remove_module

 print "Which scheme would you like to remove a module from? "
 scheme_name = gets
 $schemes.has_key?(scheme_name.chop) ? scheme_exists = true : scheme_exists = false

 if !scheme_exists
   $schemes[scheme_name.chop] = []
   puts "Scheme #{scheme_name.chop} doesn't exist"
 else
 scheme_exists = true
   puts "Which module would you like to remove from #{scheme_name.chop}?"
   $module_ID = gets
   if !$module_exists
     $schemes[$module_ID.chop] = []
     puts "Module #{$module_ID.chop} : does not exist in #{scheme_name.chop} "
   else
     module_exists = true
     puts "Module #{$module_ID.chop} has been removed from #{scheme_name.chop} "
   #  puts "Module #{module_name.chop}, #{module_ID.chop} has been added to #{scheme_name.chop} for the year #{module_year}"
 end
 end

end

When I run the program, a menu is displayed, and I select to add a module to a scheme, which calls the first method. I follow through the steps:

1. Enter scheme name -- A message is displayed stating that the scheme has been added to the system
2. Enter module name
3. Enter module ID
4. Enter academic year to which the module belongs -- A message is displayed stating that the module has been added to the scheme for that year
5. I'm asked if I want to add another module, so I say yes
6. The program runs through the same steps again, but this time skipping the first one, and starting at entering the module name -- When I've followed through the steps again, another message is displayed, stating that the second module has been added to the same scheme for whatever year I specified the second time
7. I'm then asked if I want to add another module, to which I type 'n', and am returned to the original menu.
8. This time I select the option to remove a module from a scheme
9. I'm asked which scheme I would like to remove a module from, so I enter the one I'd added the modules to
10. I'm then asked which module I would like to remove, so I enter one of the ones I had previously added to it, but I'm then told that that module does not exist in the scheme.

This suggests to me that the data I had stored in the variables when I called the first method (to add modules) has just been discarded when I called the second method (to remove modules).

How do I make sure that this information is not lost? Is there a database that I need to set up and connect my program to, or do I need to be using sessions and session variables? Or is it something completely different?

Any help would be much appreciated!

Answer 1

(Not an answer.)

I'm having problems reading your code. For example:

$schemes.has_key?(scheme_name.chop) ? scheme_exists = true : scheme_exists = false
# Did you mean:
scheme_exists = $schemes.has_key?(scheme_name.chop)

And:

if !scheme_exists
  $schemes[scheme_name.chop] = []
  puts "Scheme #{scheme_name.chop} doesn't exist"
else
  scheme_exists = true
  # ...

Why do you set scheme_exists to true? You just tested that it wasn't true.

Your "scheme exists" looks a lot like your "module exists", if they're the same, make them the same. There is a lot of chopping going on, perhaps you should just chop after input and stop chopping everywhere else–it seems error-prone and adds a lot of noise.

Overall I find it difficult to reason about your code without actually stepping through it. I'd recommend refactoring, making things read "out loud" like the problem you're trying to solve.

We also don't know if anything else touches $schemes. Whether or not you "should" be using a database depends entirely on your goals, your constraints, how you're running the app, etc. You could also serialize YAML, write a plain text file, all sorts of things.

If you restart/rerun the app you'll obviously lose all your data that isn't persisted. If you stay within the app the whole time, then it's likely either the code or your assumptions are wrong, but it's an onerous task for someone to look over the code and determine because of the way it's structured and named.