EXTENSIONS TO NUMBERS 251

Our goose/geese pair are an irregular plural, so we could tell the inflector about them using

Inflector.inflections do |inflect| inflect.irregular "goose", "geese"

end

Now Rails gets it right.

depot> ruby script/console

Loading development environment.

>>	"goose".pluralize	#=>	"geese"
>>	"geese".singularize	#=>	"goose"

Perhaps surprisingly, defining an irregular plural actually defines plurals for all words that end with the given pattern.

>>	"canadagoose".pluralize	#=>	"canadageese"
>>	"wildgeese".singularize	#=>	"wildgoose"

For families of plurals, define pattern-based rules for forming singular and plural forms. For example, the plural of father-in-law is fathers-in-law, mother- in-law becomes mothers-in-law, and so on. You can tell Rails about this by defining the mappings using regular expressions. In this case, you have to tell it both how to make the plural from the singular form and vice versa.

Inflector.inflections do |inflect|

	inflect.plural(/-in-law$/, "s-in-law")
	inflect.singular(/s-in-law$/, "-in-law")
end
>>	"sister-in-law".pluralize	#=>	"sisters-in-law"
>>	"brothers-in-law".singularize	#=>	"brother-in-law"

Some words are uncountable (like bugs in my programs). You tell the inflector using the uncountable method.

Inflector.inflections do |inflect| inflect.uncountable("air", "information", "water")

end
>>	"water".pluralize	#=>	"water"
>>	"water".singularize	#=>	"water"

In a Rails application, these changes can go in the file environment.rb in the config directory.

15.4Extensions to Numbers

Integers gain the two instance methods even? and odd?. You can also get the ordinal form of an integer using ordinalize.

puts	3.ordinalize	#=>	"3rd"
puts	321.ordinalize	#=>	"321st"

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TIME AND DATE EXTENSIONS 252

All numeric objects gain a set of scaling methods. Singular and plural forms are supported.

puts 20.bytes	#=> 20
puts 20.kilobytes	#=> 20480
puts 20.megabytes	#=> 20971520
puts 20.gigabytes	#=> 21474836480
puts 20.terabytes	#=> 21990232555520
puts 20.petabytes	#=> 22517998136852480
puts 1.exabyte	#=> 1152921504606846976

There are also time-based scaling methods. These convert their receiver into the equivalent number of seconds. The months and years methods are not accurate—months are assumed to be 30 days long, years 365 days long. However, the Time class has been extended with methods that give you accurate relative dates (see the description in the section that follows this one). Again, both singular and plural forms are supported.

puts 20.seconds	#=> 20
puts 20.minutes	#=> 1200
puts 20.hours	#=> 72000
puts 20.days	#=> 1728000
puts 20.weeks	#=> 12096000
puts 20.fortnights	#=> 24192000
puts 20.months	#=> 51840000
puts 20.years	#=> 630720000

You can also calculate times relative to some time (by default Time.now) using the methods ago and from_now (or their aliases until and since, respectively).

puts Time.now	#=> Thu May 18 23:29:14		CDT 2006
puts 20.minutes.ago	#=> Thu May 18 23:09:14		CDT 2006
puts 20.hours.from_now	#=> Fri May 19 19:29:14		CDT 2006
puts 20.weeks.from_now	#=> Thu Oct 05	23:29:14	CDT 2006
puts 20.months.ago	#=> Sat Sep 25	23:29:16	CDT 2004
puts 20.minutes.until("2006-12-25 12:00:00".to_time)
	#=> Mon Dec 25	11:40:00 UTC 2006
puts 20.minutes.since("2006-12-25 12:00:00".to_time)
	#=> Mon Dec 25	12:20:00	UTC 2006

How cool is that? And it gets even cooler....

15.5Time and Date Extensions

The Time class gains a number of useful methods, helping you calculate relative times and dates and format time strings. Many of these methods have aliases: see the API documentation for details.

now = Time.now
puts now		#=> Thu		May 18	23:36:10 CDT 2006
puts now.to_date		#=> 2006-05-18
puts	now.to_s	#=>	Thu	May 18	23:36:10 CDT 2006
puts	now.to_s(:short)	#=>	18 May 23:36

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			TIME AND DATE EXTENSIONS	253
puts now.to_s(:long)	#=> May 18,	2006 23:36
puts now.to_s(:db)	#=> 2006-05-18 23:36:10
puts now.to_s(:rfc822)	#=> Thu, 18	May 2006 23:36:10 -0500
puts now.ago(3600)	#=> Thu May	18	22:36:10 CDT 2006
puts now.at_beginning_of_day	#=> Thu May	18	00:00:00 CDT 2006
puts now.at_beginning_of_month	#=> Mon May	01	00:00:00 CDT 2006
puts now.at_beginning_of_week	#=> Mon May	15	00:00:00 CDT 2006
puts now.at_beginning_of_quarter	#=> Sat Apr	01	00:00:00 CST 2006
puts now.at_beginning_of_year	#=> Sun Jan	01	00:00:00 CST 2006
puts now.at_midnight	#=> Thu May	18	00:00:00 CDT 2006
puts now.change(:hour => 13)	#=> Thu May	18	13:00:00 CDT 2006
puts now.last_month	#=> Tue Apr	18	23:36:10 CDT 2006
puts now.last_year	#=> Wed May	18	23:36:10 CDT 2005
puts now.midnight	#=> Thu May	18	00:00:00 CDT 2006
puts now.monday	#=> Mon May	15	00:00:00 CDT 2006
puts now.months_ago(2)	#=> Sat Mar	18	23:36:10 CST 2006
puts now.months_since(2)	#=> Tue Jul	18	23:36:10 CDT 2006
puts now.next_week	#=> Mon May	22	00:00:00 CDT 2006
puts now.next_year	#=> Fri May	18	23:36:10 CDT 2007
puts now.seconds_since_midnight	#=> 84970.423472
puts now.since(7200)	#=> Fri May	19	01:36:10 CDT 2006
puts now.tomorrow	#=> Fri May	19	23:36:10 CDT 2006
puts now.years_ago(2)	#=> Tue May	18	23:36:10 CDT 2004
puts now.years_since(2)	#=> Sun May	18	23:36:10 CDT 2008
puts now.yesterday	#=> Wed May	17	23:36:10 CDT 2006
puts now.advance(:days => 30)	#=> Sat Jun	17	23:36:10 CDT 2006
puts Time.days_in_month(2)	#=> 28

puts Time.days_in_month(2, 2000) #=> 29

Date objects also pick up a few useful methods.

date = Date.today
puts date.to_s	#=> "2006-05-18"
puts date.to_time	#=> Thu May 18 00:00:00 CDT 2006
puts date.to_s(:short)	#=> "18 May"
puts date.to_s(:long)	#=> "May 18, 2006"
puts date.to_s(:db)	#=> "2006-05-18"

The last of these converts a date into a string that’s acceptable to the default database currently being used by your application. You may have noticed that the Time class has a similar extension for formatting datetime fields in a database-specific format.

You can add your own extensions to date and time formatting. For example, your application may need to display ordinal dates (the number of days into a year). The Ruby Date and Time libraries both support the strftime method for formatting dates, so you could use something like

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AN EXTENSION TO RUBY SYMBOLS 254

>> d = Date.today

=> #<Date: 4907769/2,0,2299161> >> d.to_s

=> "2006-05-29"

>> d.strftime("%y-%j") => "06-149"

Instead, though, you might want to encapsulate this formatting by extending the to_s method of dates. In your environment.rb file, add a line like the following.

ActiveSupport::CoreExtensions::Date::Conversions::DATE_FORMATS.merge!( :ordinal => "%Y-%j"

)

Now you can say

any_date.to_s(:ordinal)

#=> "2006-149"

You can extend the Time class string formatting as well.

ActiveSupport::CoreExtensions::Time::Conversions::DATE_FORMATS.merge!(

:chatty => "It's %I:%M%p on %A, %B %d, %Y"

)
Time.now.to_s(:chatty)	#=> "It's 12:49PM on Monday, May 29, 2006"

There are also two useful time-related methods added to the String class. The methods to_time and to_date return Time and Date objects, respectively.

puts	"2006-12-25	12:34:56".to_time	#=>	Mon Dec 25 12:34:56 UTC 2006
puts	"2006-12-25	12:34:56".to_date	#=>	2006-12-25

Active Support also includes a TimeZone class. TimeZone objects encapsulate the names and offset of a time zone. The class contains a list of the world’s time zones. See the Active Support RDoc for details.

15.6An Extension to Ruby Symbols

(This section describes an advanced feature of Ruby and can be safely skipped on the first dozen or so readings....)

We often use iterators where all the block does argument. We did this in our earlier group_by and

is invoke a method on its index_by examples.

groups = posts.group_by {|post| post.author_id}

Rails has a shorthand notation for this. We could have written this code as

groups = posts.group_by(&:author_id)

Similarly, the code

us_states = State.find(:all)

state_lookup = us_states.index_by {|state| state.short_name}

could also be written

us_states = State.find(:all)

state_lookup = us_states.index_by(&:short_name)

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