Compare 2 instance objects and find uncommon elements

Question

I have 2 instance objects : @original_files and @version2_files

I want to retrieve the elements found in @original_files but NOT FOUND in @version2_files.

The code below:

<% @original_files.each do |original_file| %>

  <% @version2_files.each do |ver2_file| %>
    <% if original_file.name ==  ver2_file.name%>
      <%= original_file.name %> is common to both sets
      <% break %>
      <% else %>
    <% end %>
  <% end %>

<% end %>

I would appreciate it if someone could help me figure out how to find the elements found in @original_files only.

Thanks

danh · Accepted Answer · 2012-05-01T16:01:10.283

5

They are arrays? You can subtract...

@original_files - @version2_files

Hashes can use diff.

 @original_files.diff(@version2_files)

edited May 01 '12 at 16:01

answered May 01 '12 at 15:52

danh

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FYI this method has been depricated – Carter Cole Dec 16 '15 at 18:30

score 1 · Answer 2 · answered May 01 '12 at 15:59

1

I understand this to mean that @original_files and @version2_files are hashes, and you want to find elements in @original_files that are not in @version2_files

@original_files.keys - @version2_files.keys

answered May 01 '12 at 15:59

Jesse Wolgamott

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score 1 · Answer 3 · edited May 23 '17 at 12:15

disclaimer: new to ruby and may be ignorant of how hashes/arrays work exactly.

@danh's answer is right if you want to compare on key/value pairs. But if you're comparing the 2 hashes based on their values only and the keys are not important, then diff may not be what you need. In which case, you would do something like:

original.values - version2.values => [ ... ]

which returns an array of elements found only in original but not version2.

Also, this and this may help.

Compare 2 instance objects and find uncommon elements

3 Answers3