Ruby sort_by dan uniq

Assalamualaikum


Katakan kita ada satu array

students
[
    [0] {
                   :id => 1,
             :staff_no => "A2123",
                 :name => "Ahmad Aaron",
                :phone => "2932-233-3333",
        :registered_at => "2019-12-11 12:22:22"
    },
    [1] {
                   :id => 2,
             :staff_no => "A2123",
                 :name => "Bustaman Baharun",
                :phone => "1223-231-2222",
        :registered_at => "2019-11-21 12:22:22"
    },
    [2] {
                   :id => 3,
             :staff_no => "A3123",
                 :name => "Charlie Chaplin",
                :phone => "4554-344-5554",
        :registered_at => "2018-02-16 12:22:22"
    },
    [3] {
                   :id => 4,
             :staff_no => "A2523",
                 :name => "Daruma Dorayaki",
                :phone => "5667-665-6655",
        :registered_at => "2017-06-14 12:22:22"
    },
    [4] {
                   :id => 5,
             :staff_no => "A4523",
                 :name => "Edward Elrick",
                :phone => "8778-223-9988",
        :registered_at => "2017-01-22 12:22:22"
    },
    [5] {
                   :id => 6,
             :staff_no => "A4623",
                 :name => "Frank Frederick",
                :phone => "2443-544-3445",
        :registered_at => "2017-01-22 11:01:23"
    },
    [6] {
                   :id => 7,
             :staff_no => "A2567",
                 :name => "Goro Gokurojo",
                :phone => "5667-665-6255",
        :registered_at => "2017-06-14 14:12:11"
    }
]

Bagaimana cara untuk kita susun (sort) berdasarkan tarikh dan bukan tarikh masa menggunakan Ruby? kita guna guna sort_by

students.sort_by{|s|s[:registered_at]}
[
    [0] {
                   :id => 6,
             :staff_no => "A4623",
                 :name => "Frank Frederick",
                :phone => "2443-544-3445",
        :registered_at => "2017-01-22 11:01:23"
    },
    [1] {
                   :id => 5,
             :staff_no => "A4523",
                 :name => "Edward Elrick",
                :phone => "8778-223-9988",
        :registered_at => "2017-01-22 12:22:22"
    },
    [2] {
                   :id => 4,
             :staff_no => "A2523",
                 :name => "Daruma Dorayaki",
                :phone => "5667-665-6655",
        :registered_at => "2017-06-14 12:22:22"
    },
    [3] {
                   :id => 7,
             :staff_no => "A2567",
                 :name => "Goro Gokurojo",
                :phone => "5667-665-6255",
        :registered_at => "2017-06-14 14:12:11"
    },
    [4] {
                   :id => 3,
             :staff_no => "A3123",
                 :name => "Charlie Chaplin",
                :phone => "4554-344-5554",
        :registered_at => "2018-02-16 12:22:22"
    },
    [5] {
                   :id => 2,
             :staff_no => "A2123",
                 :name => "Bustaman Baharun",
                :phone => "1223-231-2222",
        :registered_at => "2019-11-21 12:22:22"
    },
    [6] {
                   :id => 1,
             :staff_no => "A2123",
                 :name => "Ahmad Aaron",
                :phone => "2932-233-3333",
        :registered_at => "2019-12-11 12:22:22"
    }
]

Bagaimana pula untuk kita elakkan dari tarikh yang sama berulang?

kita gabungkan dengan .uniq

students.sort_by{|s|s[:registered_at]}.uniq{|q| q[:registered_at].to_date}
[
    [0] {
                   :id => 6,
             :staff_no => "A4623",
                 :name => "Frank Frederick",
                :phone => "2443-544-3445",
        :registered_at => "2017-01-22 11:01:23"
    },
    [1] {
                   :id => 4,
             :staff_no => "A2523",
                 :name => "Daruma Dorayaki",
                :phone => "5667-665-6655",
        :registered_at => "2017-06-14 12:22:22"
    },
    [2] {
                   :id => 3,
             :staff_no => "A3123",
                 :name => "Charlie Chaplin",
                :phone => "4554-344-5554",
        :registered_at => "2018-02-16 12:22:22"
    },
    [3] {
                   :id => 2,
             :staff_no => "A2123",
                 :name => "Bustaman Baharun",
                :phone => "1223-231-2222",
        :registered_at => "2019-11-21 12:22:22"
    },
    [4] {
                   :id => 1,
             :staff_no => "A2123",
                 :name => "Ahmad Aaron",
                :phone => "2932-233-3333",
        :registered_at => "2019-12-11 12:22:22"
    }
]

jadi.. untuk hanya memaparkan tarikh pendaftaran dalam satu array yang panjang, kita gabungkan sekali lagi dengan map

students.sort_by{|s|s[:registered_at]}.uniq{|q| q[:registered_at].to_date}.map{|c| c[:registered_at].to_date}
[
    [0] Sun, 22 Jan 2017,
    [1] Wed, 14 Jun 2017,
    [2] Fri, 16 Feb 2018,
    [3] Thu, 21 Nov 2019,
    [4] Wed, 11 Dec 2019
]