Find out if attributes are identical

Question

I have an array of active record objects. All objects have an attribute result and the value of result can be either 'failed' or 'passed'.

My goal is to find out if all result attributes are identical. If not then I will have to return mixed but if they are then I return the value of the attributes.

I currently have this code:

if tests.map(&:result).uniq.count != 1
   'mixed'
else
   tests.first.result
end

But that first line is quite ugly. I'm sure there is a better way to find out if all results are identical or not but I can't think of any.

\$\begingroup\$ Is it ok that tests = [] returns 'mixed'? \$\endgroup\$

tokland
– tokland

2016-07-29 08:23:17 +00:00
Commented Jul 29, 2016 at 8:23 — tokland
– tokland, Commented Jul 29, 2016 at 8:23

Flambino · Accepted Answer · 2016-07-29 10:53:40Z

2

You could try the appropriately named #all? method:

reference = tests.first.result
if tests.all? { |test| test.result == reference }
  reference
else
  'mixed'
end

Edit: As tokland points out, you'll want to check if tests is empty before any of this. Otherwise, tests.first will of course be nil.

But you could also do the check in the database layer with something like:

if Test.select(:result).distinct.count > 1
  'mixed'
else
  Test.first.try(:result)
end

Obviously you'll want to scope the query more specifically.

Also note that here, an empty collection returns a nil (because if Test.first is nil, then .try(:result) will also be nil).

edited Jul 29, 2016 at 10:53

answered Jul 29, 2016 at 4:44

Flambino

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1

\$\begingroup\$ Note that this fails when tests = [] \$\endgroup\$

tokland
– tokland

2016-07-29 08:40:08 +00:00
Commented Jul 29, 2016 at 8:40
\$\begingroup\$ @tokland Hm, yeah, good point... \$\endgroup\$

Flambino
– Flambino

2016-07-29 08:42:37 +00:00
Commented Jul 29, 2016 at 8:42

Add a comment |

tokland · Accepted Answer · 2016-07-29 19:52:16Z

2

Your code looks pretty to me. Note that there is a more efficient way to check equality for all elements in an enumerable: xs.each_cons(2).all? { |x, y| x == y }. I'd write:

results = tests.map(&:result)
if results.present? && results.each_cons(2).all? { |r1, r2| r1 == r2 }
  results.first
else
  'mixed'
end

edited Jul 29, 2016 at 19:52

answered Jul 29, 2016 at 8:32

tokland

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