ruby - 当我运行它时，sum+=n 语句中有问题，我不知道如何修复它

Question

class Test
  def multiples
    (1..1000).each do |n|
      if n % 3 == 0 || n % 5 == 0
        sum += n
      end
      puts "The sum of multiples of 3 or 5 below 1000 is #{sum}"
    end
  end
end
test = Test.new
test.multiples

错误:

test.rb:9:in `block in multiples': undefined method `+' for nil:NilClass (NoMethodError)
The sum of multiples of 3 or 5 below 1000 is 
    from test.rb:7:in `each'
    from test.rb:7:in `multiples'
    from test.rb:19:in `<top (required)>'
    from -e:1:in `load'
    from -e:1:in `<main>'

Answer 1

你还没有初始化 sum，添加 sum = 0 应该可以解决这个问题:

class Test
  def multiples
    sum = 0
    (1..1000).each do |n|
      if n % 3 == 0 || n % 5 == 0
        sum += n
      end
      puts "The sum of multiples of 3 or 5 below 1000 is #{sum}"
    end
  end
end
test = Test.new
test.multiples