红宝石类未定义方法（NoMethodError）

Question

Unfortunately, I get the following error. I can't quite understand why it doesn't work?

:14:in `convert': undefined method `factors' for 30:Fixnum (NoMethodError)
    from question_stack.rb:18:in `<main>'

I try to create the following class:

# Class Wordgame
class Wordgame
  WORDGAME_MAP = {
    '3' => 'baa',
    '5' => 'bar',
    '7' => 'bla'
  }.freeze

  def self.factors
    (1..self).select { |n| (self % n).zero? }
  end

  def self.convert(number)
    number.factors.map(&:to_s).each.map { |char| WORDGAME_MAP[char] }.join
  end
end

Wordgame.convert(30)

What am I doing wrong? Where is my mental error?

Answer 1

self refers to the class itself in a class method or to the current object in an instance method. In your case it refers to WordGame , the object's class.

If you really want it to refer to 30 into the factors method you have to define it as an instance method, because called on an object ( 30 ), not a class ( Integer ), opening the Integer class

class Integer
  def factors
    (1..self).select { |n| (self % n).zero? }
  end
end

I think you know the alternative:

def self.factors(x)
  (1..x).select { |n| (self % n).zero? }
end

def self.convert(number)
  factors(number).map(&:to_s).each.map { |char| WORDGAME_MAP[char] }.join
end

Or better, with OOP.

class WordGame
  def initialize(n)
    @n = n
  end

  def convert
    factors.map(&:to_s).each.map { |char| WORDGAME_MAP[char] }.join
  end

  private

  def factors
    (1..@n).select { |m| (@n % m).zero? }
  end
end

Wordgame.new(30).convert