I have an array ["Q10", "Q100", "Q1000", "Q1000a", "Q1001", "Q98"]
. After sorting it, I get the following result:
['Q100', 'Q1000', 'Q1000a','Q98', 'Q10', 'Q1001'].sort
["Q10", "Q100", "Q1000", "Q1000a", "Q1001", "Q98"]
Because of this behaviour, I cannot sort my ActiveRecord objects correctly. I have a model of Question
which has a field label
. I need to sort it based on label. So Question with label Q1
would be first and the question with label Q1a
would follow and so on. I get in a similar order with ActiveRecord described to the above example of array. I am using postgresql as my database.
Now I have 3 questions.
If your array were
arr = ["Q10", "Q100", "Q1000", "Q8", "Q1001", "Q98"]
you could write
arr.sort_by { |s| s[/\d+/].to_i }
#=> ["Q8", "Q10", "Q98", "Q100", "Q1000", "Q1001"]
If
s = "Q1000"
then
s[/\d+/].to_i
#=> 1000
See Enumerable#sort_by and String#[] .
The regular expression /\\d+/
matches a substring of s
that contains one or more digits.
If the array were
arr = ["Q10b", "Q100", "Q1000", "Q10a", "Q1001", "Q98", "Q10c"]
you could write
arr.sort_by { |s| [s[/\d+/].to_i, s[/\D+\z/]] }
#=> ["Q10a", "Q10b", "Q10c", "Q98", "Q100", "Q1000", "Q1001"]
If
s = "Q10b"
then
[s[/\d+/].to_i, s[/\D+\z/]]
#=> [10, "b"]
The regular expression /\\D+\\z/
matches a substring of s
that contains one or more non-digits at the end ( \\z
) of the string.
See Array#<=> , specifically the third paragraph, for an explanation of how arrays are ordered when sorting.
If the array were
arr = ["Q10b", "P100", "Q1000", "PQ10a", "Q1001", "Q98", "Q10c"]
you could write
arr.sort_by { |s| [s[/\A\D+/], s[/\d+/].to_i, s[/\D+\z/]] }
#=> ["P100", "PQ10a", "Q10b", "Q10c", "Q98", "Q1000", "Q1001"]
If
s = "PQ10a"
then
[s[/\A\D+/], s[/\d+/].to_i, s[/\D+\z/]]
#=> ["PQ", 10, "a"]
The regular expression /\\A\\D+/
matches a substring of s
that contains one or more non-digits at the beginning ( \\A
) of the string.
This should do the trick for you, casting them to numbers before sorting.
['100', '1000', '98', '10', '1001'].map(&:to_i).sort
This strange map(&:to_i)
is shorthand for map { |x| x.to_i }
map { |x| x.to_i }
Edit:
You could do this with AR. This will throw an error if the column doesn't contain a number disguised as a string.
Model.order("some_column::integer")
Edit II:
Try this if it contains strings as well.
Model.order("cast(some_column as integer))"
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