Ruby类，我怀疑我做错了实例标记

Question

我希望这个类初始化为接收要保存的消息并为其输入文件名。我绘制了一个错误，因为Ruby只希望值在init方法中实例化?温柔点，我是新手。追溯粘贴在下面。

class DobbsyKretts
  idea = 'arbitaryvalue'
  def initialize
    #Receive idea
    puts "Enter an idea, a secret or anything else you want to encrypt. Hit enter to stop typing and save the file"
    @idea.gets.reverse.upcase
    #Filename and saving - to encrypt the file.
    puts "Enter the file name you'd like to have this saved as. Type PLAN at the beginning for plans and REM for reminders"
    @file_name.gets.strip
    File::open("DobbsyKrett-"+ file_name + ".txt", "w") do |f|
      f>>@idea
    end
  end
end
something = DobbsyKretts.new

回溯:

testy.rb:11:in `initialize': private method `gets' called for nil:NilClass (NoMethodError)
    from testy.rb:21:in `new'
    from testy.rb:21:in `<main>'
Enter an idea, a secret or anything else you want to encrypt. Hit enter to stop typing and save the file

Answer 1

在分配值之前，您正在@idea上调用gets -这是您获得错误的原因之一。另外，不应该在实例变量上调用get。试试这样:

class DobbsyKretts
  def initialize
    #Receive idea
    puts "Enter an idea, a secret or anything else you want to encrypt. Hit enter to stop typing and save the file"
    (@idea = gets).reverse.upcase
    #Filename and saving - to encrypt the file.
    puts "Enter the file name you'd like to have this saved as. Type PLAN at the beginning for plans and REM for reminders"
    @file_name = gets.strip
    File::open("DobbsyKrett-"+ @file_name + ".txt", "w") do |f|
      f << @idea
    end
  end
end
something = DobbsyKretts.new

这是您所期望的，但我只是想提醒您，在构造函数中做这样的事情是一个非常糟糕的主意。您应该使用专门的方法来生成文件和/或请求用户输入。

Answer 2

gets是Kernel#gets或IO#gets(为了简洁，我将省略ARGF#gets)， @idea在您的情况下不是IO对象(默认情况下任何实例变量都设置为nil)，并且禁止使用显式接收器调用Kernel#gets。所以正确的代码是@idea = gets