How can I calculate the day of the week of a date in ruby?

Ho开发者_如何学Pythonw can I calculate the day of the week of a date in Ruby? For example, October 28 of 2010 is = Thursday

I have used this because I hated to go to the Date docs to look up the strftime syntax, not finding it there and having to remember it is in the Time docs.

require 'date'

class Date
  def dayname
     DAYNAMES[self.wday]
  end

  def abbr_dayname
    ABBR_DAYNAMES[self.wday]
  end
end

today = Date.today

puts today.dayname
puts today.abbr_dayname

Take a look at the Date class reference. Once you have a date object, you can simply do dateObj.strftime('%A') for the full day, or dateObj.strftime('%a') for the abbreviated day. You can also use dateObj.wday for the integer value of the day of the week, and use it as you see fit.

time = Time.at(time)    # Convert number of seconds into Time object.
puts time.wday    # => 0: Day of week: 0 is Sunday

Date.today.strftime("%A")
=> "Wednesday"

Date.today.strftime("%A").downcase  
=> "wednesday"

Quick, dirty and localization-friendly:

days = {0 => "Sunday",
1 => "Monday", 
2 => "Tuesday",
3 => "Wednesday",
4 => "Thursday",
5 => "Friday",
6 => "Saturday"}

puts "It's #{days[Time.now.wday]}"

Works out of the box with ruby without requiring:

Time.now.strftime("%A").downcase #=> "thursday"

As @mway said, you can use date.strftime("%A") on any Date object to get the day of the week.

If you're lucky Date.parse might get you from String to day of the week in one go:

def weekday(date_string)
  Date.parse(date_string).strftime("%A")
end

This works for your test case:

weekday("October 28 of 2010") #=> "Thursday"

Say i have date = Time.now.to_date then date.strftime("%A") will print name for the day of the week and to have just the number for the day of the week write date.wday.

In your time object, use the property .wday to get the number that corresponds with the day of the week, e.g. If .wday returns 0, then your date is Sunday, 1 Monday, etc.

basically the same answer as Andreas

days = ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday']
today_is = days[Time.now.wday]

if today_is == 'tuesday'
  ## ...
end