In Ruby on Rails, how do I format a date with the

问题:

I want to display dates in the format: short day of week, short month, day of month without leading zero but including "th", "st", "nd", or "rd" suffix.

For example, the day this question was asked would display "Thu Oct 2nd".

I'm using Ruby 1.8.7, and Time.strftime just doesn't seem to do this. I'd prefer a standard library if one exists.

回答1:

Use the ordinalize method from 'active_support'.

>> time = Time.new
=> Fri Oct 03 01:24:48 +0100 2008
>> time.strftime("%a %b #{time.day.ordinalize}")
=> "Fri Oct 3rd"

Note, if you are using IRB with Ruby 2.0, you must first run:

require 'active_support/core_ext/integer/inflections'

回答2:

You can use active_support's ordinalize helper method on numbers.

>> 3.ordinalize
=> "3rd"
>> 2.ordinalize
=> "2nd"
>> 1.ordinalize
=> "1st"

回答3:

Taking Patrick McKenzie's answer just a bit further, you could create a new file in your config/initializers directory called date_format.rb (or whatever you want) and put this in it:

Time::DATE_FORMATS.merge!(
  my_date: lambda { |time| time.strftime("%a, %b #{time.day.ordinalize}") }
)

Then in your view code you can format any date simply by assigning it your new date format:

My Date: <%= h some_date.to_s(:my_date) %>

It's simple, it works, and is easy to build on. Just add more format lines in the date_format.rb file for each of your different date formats. Here is a more fleshed out example.

Time::DATE_FORMATS.merge!(
   datetime_military: '%Y-%m-%d %H:%M',
   datetime:          '%Y-%m-%d %I:%M%P',
   time:              '%I:%M%P',
   time_military:     '%H:%M%P',
   datetime_short:    '%m/%d %I:%M',
   due_date: lambda { |time| time.strftime("%a, %b #{time.day.ordinalize}") }
)

回答4:

>> require 'activesupport'
=> []
>> t = Time.now
=> Thu Oct 02 17:28:37 -0700 2008
>> formatted = "#{t.strftime("%a %b")} #{t.day.ordinalize}"
=> "Thu Oct 2nd"

回答5:

I like Bartosz's answer, but hey, since this is Rails we're talking about, let's take it one step up in devious. (Edit: Although I was going to just monkeypatch the following method, turns out there is a cleaner way.)

DateTime instances have a to_formatted_s method supplied by ActiveSupport, which takes a single symbol as a parameter and, if that symbol is recognized as a valid predefined format, returns a String with the appropriate formatting.

Those symbols are defined by Time::DATE_FORMATS, which is a hash of symbols to either strings for the standard formatting function... or procs. Bwahaha.

d = DateTime.now #Examples were executed on October 3rd 2008
Time::DATE_FORMATS[:weekday_month_ordinal] = 
    lambda { |time| time.strftime("%a %b #{time.day.ordinalize}") }
d.to_formatted_s :weekday_month_ordinal #Fri Oct 3rd

But hey, if you can't resist the opportunity to monkeypatch, you could always give that a cleaner interface:

class DateTime

  Time::DATE_FORMATS[:weekday_month_ordinal] = 
      lambda { |time| time.strftime("%a %b #{time.day.ordinalize}") }

  def to_my_special_s
    to_formatted_s :weekday_month_ordinal
  end
end

DateTime.now.to_my_special_s  #Fri Oct 3rd

回答6:

Use %o.

Time.new( 2018, 10, 2 ).strftime( "%a %b %o" )
=> "Tue Oct 2nd"

Careful: You can't use this with DateTime:

DateTime.new( 2018, 10, 2 ).strftime( "%a %b %o" )
=> "Tue Oct %o"

But, you should be using Time anyway and this is a good reason to make the switch.