已经初始化的常量警告

Question

我使用 Nokogiri 代码提取 HTML 节点之间的文本，并在读取文件列表时收到这些错误。我使用简单的嵌入式 HTML 时没有遇到错误。我想消除或抑制这些警告，但不知道如何做。警告出现在每个块的末尾：

extract.rb:18: warning: already initialized constant EXTRACT_RANGES
extract.rb:25: warning: already initialized constant DELIMITER_TAGS

这是我的代码：

#!/usr/bin/env ruby -wKU
require 'rubygems'
require 'nokogiri'
require 'fileutils'

source = File.open('/documents.txt')
source.readlines.each do |line|
  line.strip!
  if File.exists? line
    file = File.open(line)

doc = Nokogiri::HTML(File.read(line))

# suggested by dan healy, stackoverflow 
# Specify the range between delimiter tags that you want to extract
# triple dot is used to exclude the end point
# 1...2 means 1 and not 2
EXTRACT_RANGES = [
  1...2
 ]

# Tags which count as delimiters, not to be extracted
DELIMITER_TAGS = [
  "h1",
  "h2",
  "h3"
]

extracted_text = []

i = 0
# Change /"html"/"body" to the correct path of the tag which contains this list
(doc/"html"/"body").children.each do |el|

  if (DELIMITER_TAGS.include? el.name)
    i += 1
  else
    extract = false
    EXTRACT_RANGES.each do |cur_range|
      if (cur_range.include? i)
        extract = true
        break
      end
    end

    if extract
      s = el.inner_text.strip
      unless s.empty?
        extracted_text << el.inner_text.strip
      end
    end
  end
end

print("\n")
puts line
print(",\n")
# Print out extracted text (each element's inner text is separated by newlines)
puts extracted_text.join("\n\n")
  end
end

Answer 1

如果代码缩进正确，就会更容易注意到常量定义是在循环内完成的。

比较

source.readlines.each do |line|
  # code
  if true

# Wrongly indented code

# More
# Wrongly
# Indented
# Code
EXTRACT_RANGES = [
  1...2
 ]

# Several more pages of code
  end
end

与

source.readlines.each do |line|
  # code
  if true

    # Correctly indented code

    # What is a constant doing being defined
    # this far indented?
    # Oh no - it's in a loop!

    EXTRACT_RANGES = [
      1...2
    ]

    # Several more pages of code
  end
end

Answer 2

之前没注意到。只需将常量移出每个块即可

EXTRACT_RANGES = [
  1...2
]

# Tags which count as delimiters, not to be extracted
DELIMITER_TAGS = [
 "h1",
 "h2",
 "h3"
]

source.readlines.each do |line|
 line.strip!
  if File.exists? line
    file = File.open(line)

doc = Nokogiri::HTML(File.read(line))

extracted_text = []

i = 0
# Change /"html"/"body" to the correct path of the tag which contains this list
(doc/"html"/"body").children.each do |el|

  if (DELIMITER_TAGS.include? el.name)
    i += 1
  else
    extract = false
    EXTRACT_RANGES.each do |cur_range|
      if (cur_range.include? i)
        extract = true
        break
      end
    end

    if extract
     s = el.inner_text.strip
      unless s.empty?
        extracted_text << el.inner_text.strip
      end
    end
  end
end

print("\n")
puts line
print(",\n")
# Print out extracted text (each element's inner text is separated by newlines)
puts extracted_text.join("\n\n")
  end
end

Answer 3

作为编程技巧：

在范围定义中使用 ... 与 .. 时要小心。三点版本不像两点版本那么常用，而且额外的点很容易被忽略，从而使代码更难维护。我必须有一个非常好的理由来使用三点。比较 IRB 的这些输出：

(1...2).to_a
=> [1]

与，

(1..1).to_a
=> [1]

看看第一个有多么误导。