Class: StartAt

Inherits:
Object
  • Object
show all
Includes:
Comparable
Defined in:
lib/startat.rb

Overview

StartAt is class for executing code at a specific point in the future. The object is initialized with a #DateTime object with a point of time in the future and a code block to be executed. Calling #start will calculate the wait time (in seconds), initialize a #Thread that will then sleep for the appropriate amount of time, and then the code block will be executed.

For example:

require 'date'
require 'startat'

bday = DateTime.parse("2009-08-20 08:30:00 AM EDT")
action = lambda { puts "Happy Birthday, Dad!" }
wait_for_it = StartAt.new(bday, &action)
wait_for_it.start
wait_for_it.join

StartAt was originally written to post schedule information for a symposium to Twitter (see the examples directory).

Constant Summary collapse

VERSION = 
'0.1.0'
Seconds_per_day =

:nodoc:

24 * 60 * 60

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(start_datetime, &block) ⇒ StartAt

Returns a new future action object that will execute the code block at a point in the future as defined by #start_datetime.



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# File 'lib/startat.rb', line 35

def initialize(start_datetime, &block)
  @thread_started = false
  if start_datetime.class == DateTime
    @start_datetime = start_datetime
  else
    raise ArgumentError.new("must have a DateTime object")
  end
  if block
    @action = block
  elsif block_given?
    @action = lambda { yield }
  else 
    raise ArgumentError.new("missing a block")
  end
end

Instance Attribute Details

#start_datetime ⇒ Object (readonly)

Returns the value of attribute start_datetime.



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# File 'lib/startat.rb', line 31

def start_datetime
  @start_datetime
end

Class Method Details

.get_time_after(future_datetime, time_after) ⇒ Object

Takes a future #DateTime object and returns a #DateTime object for the time after as specified in time_before in seconds.



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# File 'lib/startat.rb', line 104

def self.get_time_after(future_datetime, time_after)
  future_datetime + Rational(time_after, Seconds_per_day)
end

.get_time_before(future_datetime, time_before) ⇒ Object

Takes a future #DateTime object and returns a #DateTime object for the time before as specified in time_before in seconds.



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# File 'lib/startat.rb', line 98

def self.get_time_before(future_datetime, time_before)
  future_datetime - Rational(time_before, Seconds_per_day)
end

Instance Method Details

#<=>(other) ⇒ Object

Compares the start #DateTime of the current future action with the start time of the #other future action.



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# File 'lib/startat.rb', line 53

def <=> (other)
  @start_datetime <=> other.start_datetime
end

#cancel ⇒ Object Also known as: kill

Cancels a running future action object thread.



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# File 'lib/startat.rb', line 77

def cancel
  if ! @thread_started
    @sleeper.exit
    @thread_started = false
  end
end

#join ⇒ Object

Joins the current thread to the future action thread. See #Thread.join



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# File 'lib/startat.rb', line 92

def join
  @sleeper.join
end

#start ⇒ Object

Starts the future action thread by determining the time needed to wait based on the start date and then executes the code block once the time has elapsed.



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# File 'lib/startat.rb', line 60

def start
  if ! @thread_started
    @sleeper = Thread.new do
      wait = get_wait_time()
      # Check that the wait time is positive, otherwise the future
      # event time has already past. We skip it, since a warning
      # message was produced in wait_time.
      if wait > 0
        sleep wait
        @action.call
      end
    end
    @thread_started = true
  end
end

#status ⇒ Object

Returns the status of a future action object thread. See #Thread#status



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# File 'lib/startat.rb', line 87

def status
  @sleeper.status
end