Question

我正在编写一个脚本来为subreddit提取注释，分解单个单词，计算它们并对它们进行排序。大约70％的时间我收到此错误：

in `<main>': undefined method `map' for nil:NilClass (NoMethodError) Did you mean?  tap

大约30％的时间，脚本按预期工作。为什么会这样？你会如何解决？我是编程新手，所以如果问题是基本的话，我会感到惊讶。这是我的代码：

require 'net/http'
require 'rubygems'
require 'json'

# Pull json file, parse out comments
url = 'https://www.reddit.com/r/askreddit/comments.json?sort=top&t=all&limit=100'
uri = URI(url)
response = Net::HTTP.get(uri)
json = JSON.parse(response)

comments = json.dig("data", "children").map { |child| child.dig("data", "body") }

#Split words into array
words = comments.to_s.split(/[^'\w]+/)

words.delete_if { |a,_| a.length < 5}

#count and sort words
count = Hash.new(0)
words.each { |word| count.store(word, count[word]+1)}
count.delete_if { |_,b| b < 4}
sorted = count.sort_by { |word,count| count}.reverse
puts sorted

Answer 1

您的json.dig("data", "children")似乎偶尔会返回nil。优雅处理此问题的一种方法是使用safe navigation operator (&.)：

comments = json.dig("data", "children")&.map { |child| child.dig("data", "body") }

if comments
  # your other logic with comments here
else
  {}
end

Answer 2

Reddit方面基本上存在错误。我写了一个解决方法，但它有时会有一点延迟;它一遍又一遍地尝试直到成功。 编辑（大部分）与原始代码匹配。

require 'net/http'
require 'rubygems'
require 'json'

# Pull json file, parse out comments
url = 'https://www.reddit.com/r/askreddit/comments.json?sort=top&t=all&limit=100'
uri = URI(url)
error = true
while error
   response = Net::HTTP.get(uri)
   json = JSON.parse(response)
   error = json["error"]
end

comments = json.dig("data", "children").map { |child| child.dig("data", "body") }

#Split words into array
words = comments.to_s.split(/[^'\w]+/)

words.delete_if { |a,_| a.length < 5}

#count and sort words
count = Hash.new(0)
words.each { |word| count.store(word, count[word]+1)}
count.delete_if { |_,b| b < 4}
sorted = count.sort_by { |word,count| count}.reverse
puts sorted

Ruby - NoMethodError，但有时只为什么？

2 个答案: