Intro to the Ruby gem "Runt" as part of Squeejee's "Gem and I" series.

1. Runt
Ruby gem for building temporal expressions
squeejee Chris Lee

2. Getting started
Install from the command line:
$ sudo gem install runt
Include the library in your project
require 'rubygems' #(not necessary in Rails)
require 'runt'
include Runt
squeejee Chris Lee

3. What's a temporal expression?
For our purposes, a temporal expression can be described as a pattern*
that uses set expressions to describe recurring events or dates.
* http://martinfowler.com/apsupp/recurring.pdf
squeejee Chris Lee

4. Simple expressions
Every
week EveryTE.new(Time.now, 1, DPrecision::Precision.week)
Tues,
Thurs DIWeek.new(2) | DIWeek(Thursday)
Except
Holidays Date.new(2008, 11, 27), Date.new(2008, 12, 25)
squeejee Chris Lee

5. Putting it together
Every Tues, Except
temporal_expression week Thurs Holidays
weekly_interval = EveryTE.new(Time.now, 1, DPrecision::Precision.week)
days_in_week = DIWeek.new(2) | DIWeek.new(Thursday)
holidays = Date.new(2008, 11, 27), Date.new(2008, 12, 25)
temporal_expression = weekly_interval & days_in_week - holidays
squeejee Chris Lee

6. Matching
temporal_expression = weekly_interval & days_in_week - holidays
temporal_expression.to_s
# => quot;every 1 weeks starting Fri Oct 10
11:14:32 2008 and every Tuesday or Thursday
except for 2008-11-272008-12-25quot;
temporal_expression.include?(Date.new(2008, 10, 6)) # => false, monday
temporal_expression.include?(Date.new(2008, 10, 7)) # => true, tuesday
temporal_expression.include?(Date.new(2008, 11, 20)) # => true, thursday
temporal_expression.include?(Date.new(2008, 11, 27)) # => false # thanksgiving
temporal_expression.include?(Date.new(2008, 9, 25))
# => false why? It’s a thursday
# Use quot;REWeek.new(0, 6)quot; instead if there is no base date.
squeejee Chris Lee

7. Date ranges
Create an event that occurs every week, on Tuesdays and Thursdays, except
Thanksgiving and Christmas, for 1 year (2008).
temporal_expression.dates(DateRange.new(
PDate.day(2008, 1, 1), # start date
PDate.day(2008, 12, 31)) # end date
).each do |date
a = Activity.new(
:scheduled_at => Time.utc(date.year, date.month, date.day)
a.save
end
squeejee Chris Lee

8. More expressions
“Every 3 months, starting this month”
EveryTE.new(Time.now, 3, DPrecision::Precision.month)
“The last Thursday of a month”
DIMonth.new(Last, Thursday)
“The 12th-15th of a month”
REMonth.new(12, 15)
“December 25th of a year”
REYear.new(12, 25, 12, 25)
“3pm – 5:30pm, every Mon, Wed, and Fri”
(DIWeek.new(1) | DIWeek.new(3) | DIWeek.new(5)) & REDay.new(15,00,17,30)
squeejee Chris Lee

9. Expression builder
“Daily 8:45am to 9:30 and Fridays or Saturday except not the last Friday of
the month”
Option 1
temporal_expression = REDay.new(8,45,9,30) & DIWeek.new(Friday) |
DIWeek.new(Saturday) - DIMonth.new(Last, Friday)
Option 2
temporal_expression = ExpressionBuilder.new.define do
occurs daily_8_45am_to_9_30am
on friday
possibly saturday
except last_friday
end
squeejee Chris Lee

10. Runt resources
Rubyforge: http://runt.rubyforge.org/
Practical Ruby Gems:
Chapter 22: ‘Handling Recurring Events with runt’
squeejee Chris Lee

11. Thanks!
Drop me a line: chris.lee@squeejee.com
Web: http://squeejee.com
Blog: http://locomotivation.com
Code: http://github.com/squeejee
http://github.com/cglee
Twitter: cglee
squeejee Chris Lee