Ruby Class，我懷疑我正在做實例標記錯誤

Question

我想讓這個類初始化以接收要保存的消息併爲其輸入文件名。我是否正在繪製一個錯誤，因爲Ruby只需要在init方法中實例化值？溫柔，我是新手。 Traceback粘貼在下面。

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

所分配的值之前，您正在呼籲@ideagets - 這就是爲什麼你的錯誤的原因之一。另外，不應該在這裏調用實例變量。試着這樣說：

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 

這個工作您預期的那樣，但我只是想提醒你，這是一個非常糟糕的主意，做這樣的事情在構造函數中。您應該使用專用的方法來生成文件和/或詢問用戶輸入。

Answer 2

gets要麼是Kernel#gets或IO#gets（我將省略ARGF#gets爲簡潔起見），@idea你的情況是不是一個IO對象（默認情況下，任何實例變量設置爲nil），並調用Kernel#gets有明確的接收器被禁止。所以正確的代碼是@idea = gets。