how to take only times from dates inside array in rails - arrays

Question

so... i need to take times from dates inside Array
so for example I have an array like this
a = [
Thu, 17 Mar 2022 10:00:00.000000000 KST +09:00,
Thu, 17 Mar 2022 10:00:00.000000000 KST +09:00,
Thu, 17 Mar 2022 14:00:00.000000000 KST +09:00,
Thu, 17 Mar 2022 14:00:00.000000000 KST +09:00,
Thu, 17 Mar 2022 17:00:00.000000000 KST +09:00]
and wanted to have result of
a = ["10:00", "10:00", "14:00", "14:00", "17:00"]
So i was trying this
can_choose =[];
a.each_with_index do |time| strftime("%H:%M")
can_choose <<|time|
but doesn't works at all...
where should I have to fix??

Answer 1

You can also extract the year, month, day the same way
https://ruby-doc.org/stdlib-3.1.1/libdoc/date/rdoc/Date.html
a = [
'Thu, 17 Mar 2022 10:00:00.000000000 KST +09:00',
'Thu, 17 Mar 2022 10:00:00.000000000 KST +09:00',
'Thu, 17 Mar 2022 14:00:00.000000000 KST +09:00',
'Thu, 17 Mar 2022 14:00:00.000000000 KST +09:00',
'Thu, 17 Mar 2022 17:00:00.000000000 KST +09:00']
can_choose =[]
a.map do |time|
t = DateTime.parse(time)
can_choose << t.strftime("%k:%M")
end
p can_choose
=> ["10:00", "10:00", "14:00", "14:00", "17:00"]

Answer 2

Ruby is all about message passing. The syntax to send a message is:
receiver.message(argument)
strftime is such message, but it needs a proper receiver. So if you have some Time instance, e.g.:
time = Time.parse('2022-03-17 10:00:00 +0900')
you'd write:
time.strftime('%H:%M') #=> "10:00"
with time being the receiver, strftime being the message and '%H:%M' being the argument.
You can use the above code in an each loop like this:
can_choose = []
a.each do |time|
can_choose << time.strftime('%H:%M')
end
Or you could use map to convert your array to another array:
can_choose = a.map { |time| time.strftime('%H:%M') }
The curly braces here { ... } are equivalent to the do ... end block above.

Answer 3

I would simple go with:
can_choose = a.map { |datetime| datetime.strftime('%H:%M') }

Answer 4

If you need only hours and minutes in 24h format, just use %R directive with Time#strftime or DateTime#strftime
can_choose = a.map { |time| time.strftime('%R') }