Unusual Case Statement Behavior

TIL something weird.

I expected this to print “Integer”, but it doesn’t:

mystery_class = Integer
case mystery_class
when Integer
  p "Integer"
else
  p "Unknown"
end
# => "Unknown"

This was weird because a similar example appears to behave differently:

mystery_instance = 0
case mystery_instance
when 0
  p "Y"
else
  p "N"
end
# => "Y"

Apparently this is because []case uses === under the hood](https://stackoverflow.com/a/3908411) and === has kind of silly behavior when comparing classes.

For example:

Array === Array # false
0 === 0         # true
Class === Array # true

apparently case also works different with ActiveRecord classes, since they’ll use is_a? instead which might also behave differently??? 😱

Anyway, if you want to use case with classes for ActiveRecord object you need to do this:

mystery_class = User.last
case mystery_class
when User
  p "User"
else
  p "Unknown"
end
# => "User"