# Trouble with Pushing Arrays to Arrays **URL:** \ **Category:** Ruby\ **Created:** [April 17, 2010, 4:38pm UTC](https://www.ruby-forum.com/t/trouble-with-pushing-arrays-to-arrays/187125 "2010-04-17T16:38:43Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![derek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b38774/32.png) [@derek](https://www.ruby-forum.com/u/derek)\ **Post date:** [April 17, 2010, 4:38pm UTC](https://www.ruby-forum.com/t/trouble-with-pushing-arrays-to-arrays/187125/1 "2010-04-17T16:38:43Z")
Hello everyone! I’m having some trouble with pushing an array to another array. Maybe this is an easy fix that I’m just not seeing? Here’s my code: require ‘nokogiri’ require ‘open-uri’ url = ‘C:\users\derek\desktop\Schedule2.html’ doc = Nokogiri::HTML(open(url)) raw\_course\_list = Array.new temp = Array.new doc.css(“tr”).each { |row| # Search through every row row.css(“td”).each { |column| temp.push(column.text.strip) } # puts temp.class #=\> Array # puts temp.size #=\> 20 # puts temp[7] # E.g. =\> “Intro to Financial Accounting” raw\_course\_list.push(temp) # puts "raw\_course\_list[0]: " + raw\_course\_list[0].to\_s # \*\*\*\* Always returns the last temp pushed, not what should be at [0] (the first array ever pushed) \*\*\*\* # print "raw\_course\_list.size: ", raw\_course\_list.size, “\n” # Correctly increases +1 each push temp.clear } puts raw\_course\_list.each { |i| puts i.to\_s} # \*\*\*\* Prints out line after line of empty arrays \*\*\*\* ---
**Author:** ![derek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b38774/32.png) [@derek](https://www.ruby-forum.com/u/derek)\ **Post date:** [April 17, 2010, 4:42pm UTC](https://www.ruby-forum.com/t/trouble-with-pushing-arrays-to-arrays/187125/2 "2010-04-17T16:42:54Z")
Oh and a brief explanation: The code goes through HTML containing courses listed in tables, where each table has 20 columns of data. This segment of code ultimately is supposed to create an array of arrays – i.e. each element in raw\_course\_list is an array containing each of the 20 columns in one row of the HTML file. ---
**Author:** ![derek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b38774/32.png) [@derek](https://www.ruby-forum.com/u/derek)\ **Post date:** [April 17, 2010, 4:47pm UTC](https://www.ruby-forum.com/t/trouble-with-pushing-arrays-to-arrays/187125/3 "2010-04-17T16:47:06Z")
And one last thing: As you can see from the commented out code, the temp array is working as intended – every time the row.css(“td”).each completes, it’s filled with data from all the column in the HTML… The problem occurs (I’m guessing) when I push temp to raw\_course\_list. ---
**Author:** ![derek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b38774/32.png) [@derek](https://www.ruby-forum.com/u/derek)\ **Post date:** [April 17, 2010, 4:59pm UTC](https://www.ruby-forum.com/t/trouble-with-pushing-arrays-to-arrays/187125/4 "2010-04-17T16:59:33Z")
> The problem is that you’re reusing temp, and clearing it. Doh! I knew it was something easy. The raw\_course\_list is pushing a pointer to temp, not creating a copy of temp to push. Is this correct? ---
**Author:** ![derek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b38774/32.png) [@derek](https://www.ruby-forum.com/u/derek)\ **Post date:** [April 17, 2010, 5:02pm UTC](https://www.ruby-forum.com/t/trouble-with-pushing-arrays-to-arrays/187125/5 "2010-04-17T17:02:42Z")
> raw\_course\_list = doc.css(“tr”).map { |row| > row.css(“td”).map { |column| column.text.strip } > } Also, this coding worked perfectly. It’s very elegant; thanks! I had to look up map in the API to fully understand what was going on there 🙂 ---
**Author:** ![derek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b38774/32.png) [@derek](https://www.ruby-forum.com/u/derek)\ **Post date:** [April 17, 2010, 5:35pm UTC](https://www.ruby-forum.com/t/trouble-with-pushing-arrays-to-arrays/187125/6 "2010-04-17T17:35:36Z")
Hi – On Sat, 17 Apr 2010, Derek C. wrote: > > The problem is that you’re reusing temp, and clearing it. > > Doh! I knew it was something easy. The raw\_course\_list is pushing a > pointer to temp, not creating a copy of temp to push. Is this correct? Yes, essentially, though the more standard word in Ruby is “reference”. David – David A. Black, Senior Developer, Cyrus Innovation Inc. THE Ruby training with Black/Brown/McAnally COMPLEAT Coming to Chicago area, June 18-19, 2010! RUBYIST [http://www.compleatrubyist.com](http://www.compleatrubyist.com) ---
**Author:** ![derek](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/b38774/32.png) [@derek](https://www.ruby-forum.com/u/derek)\ **Post date:** [April 17, 2010, 4:55pm UTC](https://www.ruby-forum.com/t/trouble-with-pushing-arrays-to-arrays/187125/7 "2010-04-17T16:55:12Z")
Hi – On Sat, 17 Apr 2010, Derek C. wrote: > raw\_course\_list = Array.new > # puts "raw\_course\_list[0]: " + raw\_course\_list[0].to\_s # \*\*\*\* > Always returns the last temp pushed, not what should be at [0] (the > first array ever pushed) \*\*\*\* > # print "raw\_course\_list.size: ", raw\_course\_list.size, “\n” # > Correctly increases +1 each push > temp.clear > } > > puts raw\_course\_list.each { |i| puts i.to\_s} # \*\*\*\* Prints out line > after line of empty arrays \*\*\*\* The problem is that you’re reusing temp, and clearing it. temp = [] result = [] %w{ one two three }.each do |word| temp.push(word) result.push(temp) temp.clear end p result # =\> [[], [], []] p result.map {|obj| obj.object\_id } # =\> [606420, 606420, 606420] I end up with three copies of temp inside result, and temp is empty. Try creating the temp array inside the loop, and not clearing it. Or let Ruby do more of the work: raw\_course\_list = doc.css(“tr”).map { |row| row.css(“td”).map { |column| column.text.strip } } (if I’ve got the logic right – if not, tweak as needed 🙂 David