CODEWITHSUNDEEP
ruby
Pavel
Pavel

Reputation: 47

How to group by Date array of DateTime in pure Ruby?

I have an array of datetime objects and i need to group objects by Date (day). How can I do t with pure ruby, without gems? For example, i have array

#<DateTime: 2015-03-04T01:30:00-06:00 ((2457086j,27000s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-04T01:45:00-06:00 ((2457086j,27900s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-04T04:00:00-06:00 ((2457086j,36000s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-04T06:15:00-06:00 ((2457086j,44100s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-03T07:30:00-06:00 ((2457086j,48600s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-04T10:30:00-06:00 ((2457086j,59400s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-04T11:30:00-06:00 ((2457086j,63000s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-02T14:30:00-06:00 ((2457086j,73800s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-04T16:00:00-06:00 ((2457086j,79200s,0n),-21600s,2299161j)>

And i need to group like 

#<DateTime: 2015-03-02T14:30:00-06:00 ((2457086j,73800s,0n),-21600s,2299161j)>
-----------
#<DateTime: 2015-03-03T07:30:00-06:00 ((2457086j,48600s,0n),-21600s,2299161j)>
-----------
#<DateTime: 2015-03-04T01:30:00-06:00 ((2457086j,27000s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-04T01:45:00-06:00 ((2457086j,27900s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-04T04:00:00-06:00 ((2457086j,36000s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-04T06:15:00-06:00 ((2457086j,44100s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-04T10:30:00-06:00 ((2457086j,59400s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-04T11:30:00-06:00 ((2457086j,63000s,0n),-21600s,2299161j)>
#<DateTime: 2015-03-04T16:00:00-06:00 ((2457086j,79200s,0n),-21600s,2299161j)>

Upvotes: 1

Views: 1119

Answers (2)

Arup Rakshit
Arup Rakshit

Reputation: 118289

This is what you want:

require 'date'

# if you want day of the month 
array_of_datetimes.group_by(&:day)
# if you want the day of week 
array_of_datetimes.group_by(&:wday)

Look at the method Date#day.

Well, as Stefan addressed, OP wanted something else. But I didn't get it from the question of OP. Anyway, this is what the OP wanted finally :

array_of_datetimes.group_by(&:to_date)

Upvotes: 5

Shouichi
Shouichi

Reputation: 1150

You can use group_by from Enumerable module. See http://ruby-doc.org/core-2.2.0/Enumerable.html#method-i-group_by for more detail.

array.group_by do |datetime|
  "#{datetime.year}#{datetime.month}#{datetime.day}"
end
# => { "2015-03-03" => [...], "2015-03-04" => [...] }

Upvotes: 1

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