[LRUG] Finding the duration between two DateTimes

[Eleanor]

On 27 May 2007, at 14:17, Timothy Cowlishaw wrote:
> However, I'd still be very curious to know if this can be casted as
> some sort of class that represents a duration, rather than simply as
> an integer. Any ideas?

The simple answer is yes, assuming you want to do things with the  
duration above and beyond storing it as a time. For example, if you  
wanted to keep track of a duration whilst imposing a modifiable limit  
on it you might use the following Ruby code:

	class LimitExceeded < Exception
	end

	class Duration
		attr_writer	:length, :limit

		def initialize length = 0, limit = 0
			@length = length
			@limit = limit
		end

		def exceeds? value
			@length > value
		end

		def exceeds_limit?
			exceeds? @limit
		end

		def + time
			@length += time
			raise LimitExceeded if exceeds_limit?
		end

		def extend_limit time
			@limit += time
		end
	end

Then where you currently create your duration you could write:

	duration = Duration.new(Task.duration)

However from the perspective of a Task object you may not need any of  
this complexity. Just because something can be made into an object  
doesn't necessarily mean that it should...


Ellie

Eleanor McHugh
Games With Brains
----
raise ArgumentError unless @reality.responds_to? :reason