未定义的方法（NoMethodError）ruby

我一直收到以下错误消息：

text.rb:2:in `': undefined method `choices' for main:Object (NoMethodError) 

但我似乎无法理解为什么我的方法是“未定义的”：

 puts "Select [1] [2] [3] or [q] to quit"; users_choice = gets.chomp choices(users_choice) def choices (choice) while choice != 'q' case choice when '1' puts "you chose one!" when '2' puts "you chose two!" when '3' puts "you chose three!" end end end 

Answer 1

这是因为您在定义方法之前调用方法choices 。 编写如下代码：

 puts "Select [1] [2] [3] or [q] to quit" users_choice = gets.chomp def choices (choice) while choice != 'q' case choice when '1' break puts "you chose one!" when '2' break puts "you chose two!" when '3' break puts "you chose three!" end end end choices(users_choice) 

我用break来退出while循环。 否则它将创建一个无限循环。

Answer 2

 def main puts "Select [1] [2] [3] or [q] to quit"; users_choice = gets.chomp choices(users_choice) end def choices (choice) while choice != 'q' case choice when '1' puts "you chose one!" break when '2' puts "you chose two!" break when '3' puts "you chose three!" break end end end main 

该方法只需在执行之前调用。 这里我在main方法中包装了定义，但是在choice（）的定义之后只调用main。

Answer 3

我在Eclipse中运行Ruby时遇到了同样的错误，正在进行App Academy练习练习。 我忘了添加“对象”。 提供的测试用例。 以下语法有效：

  #!/usr/bin/ruby class Prime # Write a method that takes in an integer (greater than one) and # returns true if it is prime; otherwise return false. # # You may want to use the `%` modulo operation. `5 % 2` returns the # remainder when dividing 5 by 2; therefore, `5 % 2 == 1`. In the case # of `6 % 2`, since 2 evenly divides 6 with no remainder, `6 % 2 == 0`. # More generally, if `m` and `n` are integers, `m % n == 0` if and only # if `n` divides `m` evenly. # # You would not be expected to already know about modulo for the # challenge. # # Difficulty: medium. def primer(number) if number < 2 return false end i = 10 while i > 1 if number > i && number != i if number % i == 0 return false end end i -= 1 end return true end end object = Prime. new # These are tests to check that your code is working. After writing # your solution, they should all print true. puts("\nTests for #primer") puts("===============================================") puts('primer(2) == true: ' + (object.primer(2) == true).to_s) puts('primer(3) == true: ' + (object.primer(3) == true).to_s) puts('primer(4) == false: ' + (object.primer(4) == false).to_s) puts('primer(9) == false: ' + (object.primer(9) == false).to_s) puts("===============================================")