Weekends left til the end of summer

weekends.rb

#Author: Ian Moss aka oceanician : http://twitter.com/oceanician
#First Published: https://gist.github.com/1009253
#I'm running as part of a rails project with:
# ruby script/runner lib\weekends.rb

# Returns parameter from_date if it is a Friday.
def next_friday( from_date )
  while from_date.cwday!=5
    from_date = from_date + 1.day
  end
  from_date
end

def weekends_til( end_date )
  weekends = []
  friday_count = next_friday( Date.today )	
  while( friday_count <= end_date )
    weekends << friday_count
    friday_count = friday_count + 7.days
  end
	
  weekends
end
 
#calculate all the weekends from now, until the middle of September.
#I'm running as part of a rails project with:
# ruby script/runner lib\weekends.rb
#future = Date.today + 5.months + 3.weeks
 
# Notionally decided 21st September is the end of Summer!
future = Date.civil(y=2011, m=9, d=21)
weekends=weekends_til(future)

puts "Make the most of the next #{weekends.size} weekends until, "+future.to_s(:long)
weekends.each{|w| puts "From: Fri "+w.to_s+" to Sun " +(w+3.days).to_s}

Nothing special - and if you spot an optimisation, please do tell me it.
Just thought it might be useful for those calculating the weekends left in Summer.

Question: Where's your test coverage? :-) Took me a couple of minutes to get what you were trying to do here, test would help... :-P

So, to my eye, the variables are badly named (friday_count holds Date objects of upcoming Fridays, not a count of the number of Fridays which the name suggests - and of course in Ruby we always use arrays/hashes and then .size or ranges with .to_a.size to get a count so initially I thought you were being a C programmer who had just picked up Ruby), and I think it can be made to look/feel a little more elegant.

For example, I'd not do this as a standalone procedural program. I would have wanted to extend the Date class so I can call next_friday on any Date object and be returned the Date object of the next Friday. I'd then extend it further to add weekends_until on a Date object, perhaps returning a range or an array of dates inside the weekend instead of just the start date. That would have the advantage of being able to pull it into a Rails project and then all my Date columns having "Friday and Weekend support", or whatever.

One other refinement functionally: for most people weekends either start at 6pm on Friday or on a Saturday morning. The whole of Friday isn't included, which here it is. I'd want to tweak that. Going further, I know one guy who works 10 days on, 5 days off. Oil/gas rig workers work 2 weeks on and 2 weeks off. I think without a huge number of changes once you've extended Date or DateTime, it would be possible to return ranges of those - as appropriate, and then it becomes quite a seriously funky library to include in calendaring apps.

So, my only comments are in essence:

1. Extend Date or DateTime
2. Think a little wider outside of your definition of downtime and return ranges (or at least use ranges in the function and return an array of dates with .to_a)

Otherwise seems good to go! :-)

I agree with Paul, the naming of your variables and methods could be improved and you should have tests as well!

I'm not sure I agree that you need to be extending any classes though, if this is a simple utility function that you're using in one project, then I'd follow the principle of YAGNI and leave it at that!

I've forked the code and tweaked it a bit to use some handy ruby/activesupport bits and renamed things so they say more what they mean.

There is some ambiguity in your intent regarding the end date. For example, if the end date was a Friday, then is that weekend included? In the current implementation, the answer is yes, but that may not be what you want. Tests would help clarify this.

Wow. Thanks for the feedback. Spent about 15 minutes writing it, and I agree about the tests for sure.
I suppose a detailed comment of what I was trying to achieve would have been useful too.
Initially for creating a list of weekends I can poll mates other availability for. Then, I thought perhaps it could be used to generate doddle.ch questionnaires, then I was thinking maybe I could just create my own app on the side. Either way I thought putting the code 'out there' may actually be of use for others.
Anyways, Thanks loads for the feedback. Wanting to keep my Ruby active, so this will help a lot. I will try to evaluate it properly, and refine it. Cheers :)