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我正在用 Ruby 编写一个课程管理程序，以帮助管理大学的课程、与每门课程相关的模块以及在每个课程和模块上注册的学生。

每个学生只能注册一门课程（或计划），并且只能参加他们计划中可用的模块。

目前，我有两个类：Application.rb，这是我用作菜单的类，用于与用户交互，以及 CourseModules.rb，这是我正在做所有工作的类

应用程序.rb：

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

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

def mainMenu
  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

课程模块.rb：

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
    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，会显示菜单，然后选择选项 1（将模块添加到方案中）。然后我被要求输入方案名称，我这样做了，然后按 Enter。

但是，然后我在“has_key”的“add_module”中得到一个“未定义的方法”错误。它说它是'nil：NilClass（NoMethodError）

谁可以给我解释一下这个？我该怎么说呢？

4

1 回答 1

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您正在参考，@schemes但您将其定义为schemes = {}，因此nil:NilClass (NoMethodError).

于 2012-08-21T20:18:00.287 回答