How to print elements with same Xpath below same column (same header) - ruby

Question

I'm trying to parse an XML file with REXML on Ruby.
What I want is print all values and the corresponding element name as header. The issue I have
is that some nodes have child elements that appear repeated and have the same Xpath, so for those
elements I want to printing in the same column. Then for the small sample below, the output desired
for the elements of Node_XX would be:
Output I'm looking for:
RepVal|YurVal|CD_val|HJY_val|CD_SubA|CD_SubB
MTSJ|AB01-J|45|01|87|12
||34|11|43|62
What I have so far is the code below, but I don´t know how to do in order repeated
elements be printed in the same column.
Thanks in advance for any help.
Code I have so far:
#!/usr/bin/env ruby
require 'rexml/document'
include REXML
xmldoc = Document.new File.new("input.xml")
arr_H_Xpath = [] # Array to store only once all Xpath´s (without Xpath repeated)
arr_H_Values = [] # Array for headers (each child element´s name)
arr_Values = [] # Values of each child element.
xmldoc.elements.each("//Node_XYZ") {|element|
element.each_recursive do |child|
if (child.has_text? && child.text =~ /^[[:alnum:]]/) && !arr_H_Xpath.include?(child.xpath.gsub(/\[.\]/,"")) # Check if element has text and Xpath is stored in arr_H_Xpath.
arr_H_Xpath << child.xpath.gsub(/\[.\]/,"") #Remove the [..] for repeated XPaths
arr_H_Values << child.xpath.gsub(/\/\w.*\//,"") #Get only name of child element to use it as header
arr_Values << child.text
end
print arr_H_Values + "|"
arr_H_Values.clear
end
puts arr_Values.join("|")
}
The input.xml is:
<TopNode>
<NodeX>
<Node_XX>
<RepCD_valm>
<RepVal>MTSJ</RepVal>
</RepCD_valm>
<RepCD_yur>
<Yur>
<YurVal>AB01-J</YurVal>
</Yur>
</RepCD_yur>
<CodesDif>
<CD_Ranges>
<CD_val>45</CD_val>
<HJY_val>01</HJY_val>
<CD_Sub>
<CD_SubA>87</CD_SubA>
<CD_SubB>12</CD_SubB>
</CD_Sub>
</CD_Ranges>
</CodesDif>
<CodesDif>
<CD_Ranges>
<CD_val>34</CD_val>
<HJY_val>11</HJY_val>
<CD_Sub>
<CD_SubA>43</CD_SubA>
<CD_SubB>62</CD_SubB>
</CD_Sub>
</CD_Ranges>
</CodesDif>
</Node_XX>
<Node_XY>
....
....
....
</Node_XY>
</NodeX>
</TopNode>

Answer 1

Here's one way to solve your problem. It is probably a little unusual, but I was experimenting. :)
First, I chose a data structure that can store the headers as keys and multiple values per key to represent the additional row(s) of data: a MultiMap. It is like a hash with multiple keys.
With the multimap, you can store the elements as key-value pairs:
data = Multimap.new
doc.xpath('//RepVal|//YurVal|//CD_val|//HJY_val|//CD_SubA|//CD_SubB').each do |elem|
data[elem.name] = elem.inner_text
end
The content of data is:
{"RepVal"=>["MTSJ"],
"YurVal"=>["AB01-J"],
"CD_val"=>["45", "34"],
"HJY_val"=>["01", "11"],
"CD_SubA"=>["87", "43"],
"CD_SubB"=>["12", "62"]}
As you can see, this was a simple way to collect all the information you need to create your table. Now it is just a matter of transforming it to your pipe-delimited format. For this, or any delimited format, I recommend using CSV:
out = CSV.generate({col_sep: "|"}) do |csv|
columns = data.keys.to_a.uniq
csv << columns
while !data.values.empty? do
csv << columns.map { |col| data[col].shift }
end
end
The output is:
RepVal|YurVal|CD_val|HJY_val|CD_SubA|CD_SubB
MTSJ|AB01-J|45|01|87|12
||34|11|43|62
Explanation:
CSV.generate creates a string. If you wanted to create an output file directly, use CSV.open instead. See the CSV class for more information. I added the col_sep option to delimit with a pipe character instead of the default of a comma.
Getting a list of columns would just be the keys if data was a hash. But since it is a Multimap which will repeat key names, I have to call .to_a.uniq on it. Then I add them to the output using csv << columns.
In order to create the second row (and any subsequent rows), we slice down and get the first value for each key of data. That's what the data[col].shift does: it actually removes the first value from each value in data. The loop is in place to keep going as long as there are more values (more rows).