From: Chris Roos <chris@...>
Date: 2005-07-29T19:42:48+09:00
Subject: Re: add_weekdays method

Todd wrote:
> Todd wrote:
> 
>>Chris Roos wrote:
>>
>>>Hi,
>>>
>>>I've just spent some time looking at an add_weekdays method on the Date
>>>class.
>>>
>>>My implementation is as follows.
>>>
>>>class Date
>>>   def add_weekdays(days)
>>>     new_date = self
>>>     while days > 0
>>>       new_date += 1
>>>       days -= 1 unless (new_date.wday == 6 || new_date.wday == 0)
>>>     end
>>>     new_date
>>>   end
>>>end
>>>
>>>I'm interested to know whether I've a) wasted my time because I could
>>>have achieved the same thing with an already available object/method b)
>>>commited any ruby sins and c) whether there are much better ways of
>>>implementing this?
>>>
>>>Chris
>>
>>Looks like you want to skip weekends.  I might do it this way...
>>
>>class Date
>>  def add_weekdays(days)
>>    new_date = self
>>    days.times { new_date += ( new_date.wday == 6 ? 3 : 1 ) }
>>  end
>>end
> 
> 
> Don't listen to that piece of code.  I thought I tested it, but now
> that I try it, it fails.  Here we go:
> 
> class Date
>   def add_weekdays(days)
>     new_date = self
>     days.times { new_date += ( new_date.wday==5 ? 3 ( new_date.wday==6
> ? 2 : 1 ) ) }
>     return new_date
>   end
> end
> 
> puts Date.today.add_weekdays(4)
> #or whatever number
> 
> Basically, if it's Friday, add 3, if it's Saturday add 2, otherwise add
> 1.
> 
> Like I said, though, your loop algorithm should work well.
> 
> Todd
> 
Thanks for the alternative implementation Todd.  I'm still running with 
my original but I've changed it ever so slightly, as it's now in the 
Time class rather than Date, and therefore I'm first creating a new 
DateTime and then adding days to it.

def add_weekdays(days)
   new_date = DateTime.new(self.year, self.month, self.day, self.hour, 
self.min, self.sec)
   while days > 0
     new_date += 1
     days -= 1 unless (new_date.wday == 6 || new_date.wday == 0)
   end
   new_date
end

I'm pretty certain it doesn't, but, on the off chance it makes a 
difference this is to be used in a Rails app.

Chris