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我正在编写我的第一个 Ruby on Rails 程序，这是一个帮助管理/组织大学课程、参加课程的学生以及属于每个课程的模块的应用程序。

我目前有两个类：第一个类，称为 Application，是我用来与用户交互的类，如下所示：

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.addModuleToScheme
  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

第二个，称为 courseModules 是我将用来允许用户添加新课程并向这些课程添加模块的一个。这个类目前看起来像这样：

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

   def addModule
     moduleName = Module.new(30)
     moduleRefNo = Random(100)
     #moduleTitle = @moduleTitle
     moduleYear(4)

     print "What is the name of the module you would like to add?"
     moduleName = gets
     moduleRefNo
     printf "Which year does the module belong to?"
     @@moduleYear = gets
     puts "#{moduleName}, belonging to #{@@moduleYear} has been added to the system, with reference number #{moduleRefNo}."
     navigateTo Application

   end

   def addModuleToScheme

     # Create an empty hash for the schemes
     schemes = Hash.new()

     # Allow user to enter scheme names into a set of variables, and use each scheme name as a hash/ array of modules.
     # Then allow the user to enter the the modules for each scheme into each of the hashes

     # Create specific hash elements by using the following line:
     schemes = {:scheme1 => scheme1variable, :scheme2 => scheme2variable}

     puts "What is the name of the scheme that you would like to add a module to? "
     schemeName = gets

     # Need to use an if statement here to check whether or not the scheme already exists, if it doesn't, create it, if it does,
     # tell the user that it does.

     if schemes.has_key?(schemeName)
       puts "This scheme has already been added "
     else
       schemes.add(schemeName)
     end

     noOfModulesInScheme + 1
     moduleName.moduleScheme = schemeName
   end

   def removeModuleFromScheme
     moduleName.moduleScheme = nil
   end

   def queryModule

   end

 end

目前，我正在处理菜单中的第一个选项 - “将模块添加到方案”。当我尝试从 Application.rb 类运行程序时，会显示菜单，我输入：“1”，这是我要选择的选项。

但是，然后我收到一条错误消息，说我的方法“addModuleToScheme”未定义。有人可以指出我的“addModuleToScheme”方法做错了什么吗？

非常感谢。

编辑 21/08/2012 00:35

好的，我认为这似乎已经解决了我的 addModuleToScheme 方法，但是当我尝试将方案名称实际添加到哈希时出现错误：

当我现在从菜单中选择“1”时，系统会要求我输入方案的名称，但是，当我输入该名称时，会出现未定义的方法错误，

undefined method 'add' for {}:Hash (NoMethodError)"

在线上

schemes.add(schemeName)

在我的 if else 语句中。有什么想法我在这里做错了吗？

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1 回答 1

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我敢打赌它告诉你这CourseModules.addModuleToScheme是未定义的。那是因为当您尝试将其用作类方法时，您已经将该方法实现为实例方法。

尝试将其定义为：

def self.addModuleToScheme
  # ... do stuff
end

或尝试将其用作实例方法，在这种情况下，您必须首先创建CourseModules该类的新实例。

于 2012-08-20T20:09:20.657 回答