Good notes posted by mindloaf

Complete Formatting Codes

NOTE: Some of these seem only to work for DateTime (e.g. %L, %N)

%a - The abbreviated weekday name (“Sun”)

%A - The full weekday name (“Sunday”)

%b - The abbreviated month name (“Jan”)

%B - The full month name (“January”)

%c - The preferred local date and time representation

%C - Century (20 in 2009)

%d - Day of the month (01..31)

%D - Date (%m/%d/%y)

%e - Day of the month, blank-padded ( 1..31)

%F - Equivalent to %Y-%m-%d (the ISO 8601 date format)

%h - Equivalent to %b

%H - Hour of the day, 24-hour clock (00..23)

%I - Hour of the day, 12-hour clock (01..12)

%j - Day of the year (001..366)

%k - hour, 24-hour clock, blank-padded ( 0..23)

%l - hour, 12-hour clock, blank-padded ( 0..12)

%L - Millisecond of the second (000..999)

%m - Month of the year (01..12)

%M - Minute of the hour (00..59)

%n - Newline (n)

%N - Fractional seconds digits, default is 9 digits (nanosecond)

• %3N millisecond (3 digits)

• %6N microsecond (6 digits)

• %9N nanosecond (9 digits)

%p - Meridian indicator (“AM” or “PM”)

%P - Meridian indicator (“am” or “pm”)

%r - time, 12-hour (same as %I:%M:%S %p)

%R - time, 24-hour (%H:%M)

%s - Number of seconds since 1970-01-01 00:00:00 UTC.

%S - Second of the minute (00..60)

%t - Tab character (t)

%T - time, 24-hour (%H:%M:%S)

%u - Day of the week as a decimal, Monday being 1. (1..7)

%U - Week number of the current year, starting with the first Sunday as the first day of the first week (00..53)

%v - VMS date (%e-%b-%Y)

%V - Week number of year according to ISO 8601 (01..53)

%W - Week number of the current year, starting with the first Monday as the first day of the first week (00..53)

%w - Day of the week (Sunday is 0, 0..6)

%x - Preferred representation for the date alone, no time

%X - Preferred representation for the time alone, no date

%y - Year without a century (00..99)

%Y - Year with century

%z - Time zone as hour offset from UTC (e.g. +0900)

%Z - Time zone name

%% - Literal “%” character

t = Time.now                        #=> 2007-11-19 08:37:48 -0600
t.strftime("Printed on %m/%d/%Y")   #=> "Printed on 11/19/2007"
t.strftime("at %I:%M%p")            #=> "at 08:37AM"

Hash#except

Note that the ActiveSupport library provides the except and except! methods, which return the Hash minus the given keys. So you don’t need to write your own wrapper if you happen to be using Rails or ActiveSupport as a stand-alone library:

http://apidock.com/rails/ActiveSupport/CoreExtensions/Hash/Except/except

Create a Hash from two Arrays

Here is my favorite idiom for creating a Hash from an Array of keys and an Array of values:

keys = [:a, :b]
values = [1,2]
h = Hash[*keys.zip(values).flatten]      # => {:b=>2, :a=>1}

Test if one array includes the elements of another

You can just use a set difference (aka minus) to see if one array includes all elements of another

not_included = [1,2,3] - (1..9).to_a
not_included      # => []

not_included = [1,2,3,'A'] - (1..9).to_a
not_included      # => ["A"]

Use intersection to test if any of the one are in the other:

shared = [1,2,3,'A'] & (1..9).to_a
shared     # => [1, 2, 3]