I'm trying to get an array of month names from the last 6 months. I've seen other posts that address iterating and printing actual dates 7/1/16, 7/2/16, etc., but nothing that just does month names:
["February", "March", "April", "May", "June" ,"July"]
I was trying the following code, but I get this error:
@array = []
(6.months.ago..Time.now).each do |m|
@array.push(Date::MONTHNAMES[m])
end
TypeError: can't iterate from ActiveSupport::TimeWithZone
A slightly uglier version that builds on Olives' answer , but doesn't require looking up dates in each month and is about 31x faster:
current_month = Date.today.month
month_names = 6.downto(1).map { |n| DateTime::MONTHNAMES.drop(1)[(current_month - n) % 12] }
Output when current_month
is 4 (to test Dec-Jan rollover):
["November", "December", "January", "February", "March", "April"]
Benchmark:
Benchmark.measure do
10000.times do
current_month = Date.today.month
month_names = 6.downto(1).map { |n| DateTime::MONTHNAMES.drop(1)[(current_month - n) % 12] }
end
end
=> #<Benchmark::Tms:0x007fcfda4830d0 @label="", @real=0.12975036300485954, @cstime=0.0, @cutime=0.0, @stime=0.07000000000000006, @utime=0.06999999999999984, @total=0.1399999999999999>
Compare to the cleaner version:
Benchmark.measure do
10000.times do
5.downto(0).collect do |n|
Date::MONTHNAMES[n.months.ago.month]
end
end
end
=> #<Benchmark::Tms:0x007fcfdcbde9b8 @label="", @real=3.7730263769917656, @cstime=0.0, @cutime=0.0, @stime=0.04999999999999993, @utime=3.69, @total=3.7399999999999998>
A simple, although a bit naive way, would be to iterate over integers and calculate which month it falls into and then finally look it up in the array.
5.downto(0).collect do |n|
Date::MONTHNAMES[n.months.ago.month]
end
This will return ["February", "March", "April", "May", "June", "July"]
(This is being executed in July)
Below Version will display in 3 character month format:
5.downto(0).collect do |n|
Date.parse(Date::MONTHNAMES[n.months.ago.month]).strftime('%b')
end
Output: (considering current month as January)
["Aug", "Sep", "Oct", "Nov", "Dec", "Jan"]
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