Using .sort_by to sort a nested array

Question

I have a nested array that I want to sort by a specific object, some advice would be very much appreciated.

In this example I'd like the output to return sorted by the dates that are nested.

arr =    [
           [
             {  
               "log"=>[
                 [
                   "2016-09-03T00:00:00-03:00",
                 ],
                 [
                   "2016-09-01T00:00:00-03:00",
                 ],
                 [
                   "2016-09-02T00:00:00-03:00",
                 ]
               ]
             }
           ]
         ]

When you give an example it is helpful to assign a variable to each input object (e.g., arr = [[{ "log"=>....). That way readers can refer to the variable in answers and comments without having to define it. — Cary Swoveland
– Cary Swoveland, Commented Nov 15, 2016 at 0:47

Cary Swoveland · Accepted Answer · 2016-11-15 01:29:10Z

3

arr = [
        [
          {  
            "log"=>[
               ["2016-09-03T00:00:00-03:00"],
               ["2016-09-01T00:00:00-03:00"],
               ["2016-09-02T00:00:00-03:00"]
            ]
          }
        ]
      ]

To return a sorted array and not mutate arr:

[[{ "log"=>arr[0][0]["log"].sort_by(&:first) }]]
  #=> [[{"log"=>[
  #       ["2016-09-01T00:00:00-03:00"],
  #       ["2016-09-02T00:00:00-03:00"],
  #       ["2016-09-03T00:00:00-03:00"]
  #   ]}]]

To sort in place:

arr[0][0]["log"] = arr[0][0]["log"].sort_by(&:first)
  #=> [["2016-09-01T00:00:00-03:00"],
  #    ["2016-09-02T00:00:00-03:00"],
  #    ["2016-09-03T00:00:00-03:00"]] 
arr
  #=> [[{"log"=>[
  #       ["2016-09-01T00:00:00-03:00"],
  #       ["2016-09-02T00:00:00-03:00"],
  #       ["2016-09-03T00:00:00-03:00"]
  #   ]}]]

edited Nov 15, 2016 at 1:29

answered Nov 15, 2016 at 0:35

Cary Swoveland

111k6 gold badges69 silver badges105 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Jim Stewart Over a year ago

This is only going to work on that single array element. If either of the two outer arrays have multiple elements, it's only going to handle the first one.

Cary Swoveland Over a year ago

@Jim, yes, that's true, and something I mulled in preparing my answer. The problem is that to deal with a more general case additional specification would be required. Suppose, for example,

arr = [[{ "log"=>[ ["2016-09-03T00:00:00-03:00"], ["2016-09-01T00:00:00-03:00"]] }], [{  "log"=>[ ["2015-08-03T00:00:00-03:00"], ["2015-08-01T00:00:00-03:00"]] }]]

. In this case it's not clear what is wanted.

Collectives™ on Stack Overflow

Using .sort_by to sort a nested array

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related