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我正在使用 Ruby on Rails 编写一个程序，以允许用户管理大学课程、他们的模块以及注册这些课程的学生。

目前，我有两个类：Application.rb 和 CourseModules.rb：

Application.rb 是我用来与用户交互的类——它目前看起来像这样：

代码：

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

CourseModules.rb 是我做所有工作的地方——它目前看起来像这样：

代码：

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

目前，当我从 Application.rb 运行程序时，我会看到菜单，我选择选项 1：“将模块添加到方案”

然后我被要求输入一个方案名称，我这样做了，然后出现一条线，告诉我该方案已添加到系统中。

接下来，我被要求输入模块的名称，我这样做了，然后被问到是否要输入另一个模块。如果我输入“y”或“yes”，我可以输入另一个模块的名称。但是，如果我输入“n”或除“y”或“yes”以外的任何内容，程序就会崩溃，并且在控制台中会出现一些错误。

这些错误中的第一个说：

在add_module': undefined methodmain_menu' 中为 Application:Class (NoMethodError)

在线上：

Application.main_menu

在里面

def self.add_module

我的 CourseModules.rb 类中的方法。

应该发生的情况是，当用户在询问他们是否要添加另一个模块时输入“n”或“y”或“yes”以外的任何内容时，他们应该被收回程序主菜单。

有谁知道我在这里做错了什么？我怎样才能把它正确？

4

1 回答 1

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.

于 2012-08-22T11:42:31.077 回答