Question

I am writing a program using Ruby on Rails to allow users to manage University courses, their modules, and the students enrolled on them.

Currently, I have two classes: Application.rb and CourseModules.rb:

Application.rb is the class that I am using to interface with the user- it currently looks like this:

Code:

class Application
# To change this template use File | Settings | File Templates.
require './courseModules.rb'
def initialize
  main_menu
end

=begin
  def navigateTo(what)
  what.new(v).display
  mainMenu
  end
=end

def main_menu
  puts "What would you like to do?
      1: Add module to a scheme
      2: Remove module from a scheme
      3: Query modules
      4: Modify module
      5: Register a student on a scheme
      6: Remove a student from a scheme
      7: Register a student on a module
      8: Remove a student from a module"
  case gets.strip
    when "1"
      CourseModules.add_module
    when "2"
      CourseModules.removeModuleFromScheme
    when "3"
      navigateTo CourseModules
    when "4"
      navigateTo CourseModules
    when "5"
      navigateTo Student
    when "6"
      navigateTo Student
    when "7"
      navigateTo Student
    end
  end
  Application.new
end

and CourseModules.rb is where I am doing all of the work- it currently looks like this:

Code:

class CourseModules
# To change this template use File | Settings | File Templates.
   @@moduleScheme = nil
   @@moduleYear = nil
   #@moduleTitle = ""
   @noOfModulesInScheme = 0

   def self.moduleYear
     @@moduleYear
   end

   def initialize(v)
     @val = v
   end
   # Set and get the @val object value
   def set (v)
     @val = v
   end
   def get
     return @val
   end


# Attempt at add_module method on 21/08/2012 at 16:30
def self.add_module
  schemes = {}
  scheme_exists = false
  add_another_scheme = true
  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"
   else
     scheme_exists = false
     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
     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

 print "Add another scheme? "
 ask_if_user_wants_to_add_another_scheme = gets
 if !(ask_if_user_wants_to_add_another_scheme.chop == "y" or ask_if_user_wants_to_add_another_scheme.chop == "yes")
   add_another_scheme = false
 end
 puts @schemes

end

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

   if !scheme_exists
     print "Enter module name: "
     module_name = gets
     schemes[scheme_name.chop] = module_name.chop
     puts "Scheme #{scheme_name.chop} with module #{module_name} has been added to the system"
   else
     scheme_exists = false
     puts "This scheme has already been added"
     puts "Enter module name: "
     module_name = gets
     schemes[scheme_name.chop] = module_name.chop
     puts "Scheme #{scheme_name.chop} with module #{module_name} has been added to the system"
   end

   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.chop == "yes")
     add_another_module = false
   end
 end
 puts schemes
end

end

At present, when I run the program from Application.rb, I am presented with the menu, and I choose option 1: “Add module to a scheme”

I am then asked to enter a scheme name, which I do, and a line appears telling me that the scheme has been added to the system.

Next, I am asked to enter the name of the module, which I do, and am then asked if I’d like to enter another module. If I type ‘y’ or ‘yes’, I am allowed to enter the name of another module.
However, if I type ‘n’ or anything other than ‘y’ or ‘yes’, the program crashes and I get a few errors in the console.

The first of these errors says:

in add_module': undefined methodmain_menu’ for Application:Class (NoMethodError)

on the line:

Application.main_menu

in the

def self.add_module

method in my CourseModules.rb class.

What should happen is that when the user enters ‘n’ or anything other than ‘y’ or ‘yes’ when asked if they’d like to add another module, they should be taken back the program main menu.

Does anyone have any idea what I’m doing wrong here? How can I put it right?

Answer 1

It looks like you are trying to call a class method with Application.main_menu when it is defined as an instance method on the Application class which is why you are getting an undefined_method. Try adding self to the main_menu method definition.

class Application
  def self.main_menu
    ....
  end
end

Fix based on your comments:

You will need to modify the initialize method as well. You can do so by changing it to this

class Application
  def initialize
    self.class.main_menu
  end

  ...

end

By adding just self before main_menu in the initialize method you are just telling initialize that you want to initialize a new method when you create a new Application class. In order to tell initialize that you want this method to be a class method you need to pass in the class as well. I hope this makes sense.