[语法]在代码块中报错说undefined method `+'

Question

class RubyLearning
  def test_each
    dirs = Dir.glob('*')
    dirs.each { |dir| @dirs += ( dir + '\n' )}
    puts @dirs
  end

end

RubyLearning.new.test_each

 

错误信息

NoMethodError: undefined method `+' for nil:NilClass

method test_each in ruby_learning.rb at line 4
method each in ruby_learning.rb at line 4
method test_each in ruby_learning.rb at line 4
at top level in ruby_learning.rb at line 10

Program exited with code #1 after 0.04 seconds.

  本来该提问的，可是积分不够，望Admin手下留情

Answer 1

@dirs还不存在吧……几乎可以肯定你这里的@dirs是nil。
在你的test_each开头处加句
[code="ruby"]@dirs ||= ''[/code]

不过这里用实例成员变量有意义么……