Ruby：为什么数组中所有字符串的末尾都有一个“ nil”？ [英] Ruby: Why is there a `nil` at the end of all the strings in my array?

问题描述

因此，我用Ruby编写了一些代码，将文本文件分成几行，然后根据分隔符将这些行分组。然后将此输出写入数组，该数组将传递给方法，该方法将HTML吐出到文本文件中。当我尝试以不同的方法使用gsub替换HTML文本文件中的占位符时，出现了问题，这些值来自 record 数组-Ruby一直告诉我我正在传递以零值表示。在尝试调试程序的该部分几个小时后，我决定将目光转向其他地方，我认为自己正在做些事情。该程序的修改版本发布在下面。

So I've written some code in Ruby to split a text file up into individual lines, then to group those lines based on a delimiter character. This output is then written to an array, which is passed to a method, which spits out HTML into a text file. I started running into problems when I tried to use gsub in different methods to replace placeholders in a HTML text file with values from the record array - Ruby kept telling me that I was passing in nil values. After trying to debug that part of the program for several hours, I decided to look elsewhere, and I think I'm on to something. A modified version of the program is posted below.

以下是输入文本文件的示例：

Here is a sample of the input text file:

26188
WHL
1
Delco

B-7101
A-63
208-220/440
3
285  w/o pallet
1495.00

C:/img_converted/26188B.jpg
EDM Machine Part 2 of 3
AC Motor, 3/4 Hp, Frame 182, 1160 RPM
|--|--|--|--|--|--|--|--|--|--|--|--|--|--|--|--|

这是我一直在测试的代码的一个片段：

Here is a snippet of the code that I've been testing with:

# function to import file as a string

def file_as_string(filename)
    data = ''
    f = File.open(filename, "r")
    f.each_line do |line|
    data += line
end
return data
end

Dir.glob("single_listing.jma") do |filename|
content = file_as_string(filename)
content = content.gsub(/\t/, "\n")
database_array = Array.new
database_array = content.split("|--|--|--|--|--|--|--|--|--|--|--|--|--|--|--|--|")
for i in database_array do
    record = Array.new
    record = i.split("\n")
    puts record[0]
    puts record[0].class     end
end

运行该代码后，我得到此输出：

When that code is run, I get this output:

john@starfire:~/code/ruby/idealm_db_parser$ ruby putsarray.rb
26188
String
nil
NilClass

...这意味着每个数组记录中的位置显然具有类型为 String 和类型为无。为什么？

... which means that each array position in record apparently has data of type String and of type nil. why is this?

推荐答案

您的 database_array 具有比您想象的更多的维度。

Your database_array has more dimensions than you think.

您的节结尾标记 |-| ----...... |-| 之后有换行符。因此， file_as_string 返回如下内容：

Your end-of-stanza marker, |--|--|...|--| has a newline after it. So, file_as_string returns something like this:

"26188\nWHL...|--|--|\n"

然后是 split（）在节末变成这样：

and is then split() on end-of-stanza into something like this:

["26188\nWHL...1160 RPM\n", "\n"]  # <---- Note the last element here!

然后您又将它们分开，但 \n .split（ \n）给出一个空数组，其第一个元素返回为 nil 。

You then split each again, but "\n".split("\n") gives an empty array, the first element of which comes back as nil.

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