ruby - 如何为 nil 类错误调试未定义的方法？

Question

我正在尝试使用 cardmagic 分类器 gem 创建一个分类器。这是我的代码:

require 'classifier'

classifications = '1007.09', '1006.03'
traindata = Hash["1007.09" => "ADAPTER- SCREENING FOR VALVES VBS", "1006.03" => "ACTUATOR- LINEAR"]

b = Classifier::Bayes.new classifications

traindata.each do |key, value|  
b.train(key, value)
end 

但是当我运行它时，出现以下错误:

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c:/Ruby192/lib/ruby/gems/1.9.1/gems/classifier-1.3.3/lib/classifier/bayes.rb:27:in `block in train': undefined method `[]' for nil:NilClass (NoMethodError)
  from c:/Ruby192/lib/ruby/gems/1.9.1/gems/classifier-1.3.3/lib/classifier/bayes.rb:26:in `each'
  from c:/Ruby192/lib/ruby/gems/1.9.1/gems/classifier-1.3.3/lib/classifier/bayes.rb:26:in `train'
  from C:/_Chris/Code/classifier/smdclasser.rb:13:in `block in <main>'
  from C:/_Chris/Code/classifier/smdclasser.rb:11:in `each'
  from C:/_Chris/Code/classifier/smdclasser.rb:11:in `<main>'

这是 gem 代码的来源:

# Provides a general training method for all categories specified in Bayes#new
# For example:
#     b = Classifier::Bayes.new 'This', 'That', 'the_other'
#     b.train :this, "This text"
#     b.train "that", "That text"
#     b.train "The other", "The other text"
def train(category, text)
  category = category.prepare_category_name
  text.word_hash.each do |word, count|
    @categories[category][word]     ||=     0
    @categories[category][word]      +=     count
    @total_words += count
  end
end

我不知道去哪里解决这个错误，下一步我应该做什么？

Answer 1

Classifier::Bayes.new 需要一个展开的值数组，而不是单个参数。例如，请注意示例代码使用:

b = Classifier::Bayes.new 'This', 'That', 'the_other'

而不是:

b = Classifier::Bayes.new ['This', 'That', 'the_other']

传入 classifications 数组的 splat 版本，它应该可以工作:

b = Classifier::Bayes.new *classifications