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

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??

CodePudding user response：

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"]

CodePudding user response：

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.

CodePudding user response：

I would simple go with:

can_choose = a.map { |datetime| datetime.strftime('%H:%M') }

CodePudding user response：

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') }