Hello, This may just be my misunderstanding something, but I''m seeing something strange. I have a model, Ticket, that in the database table ''tickets'' has a field, let''s say ''seats''. I can do a Find and retrieve the items: t = Ticket.find :all Then do a sum to get the total seats: s = t.sum(&:seats) and that returns the correct sum. Playing in the console, I did: t.sum(&:seats) and while returning the correct sum, it also changed the ''t'' variable to be just the final item in the array. Is this correct? The sum is just doing an ''inject'', which I didn''t think altered the original array, but maybe I''m wrong? And here''s a second question, say I want to use the found items, but restrict the sum to a subset - total all seats that have been sold. I could do it by doing another find, but can I use .inject with a condition, so I don''t have to requery the database? Thanks! --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Hmm, not sure on the console based sum findings, I don''t see the same
behavior. On your other question, the sum methods, etc all use
ActiveRecord::Calculations#calculate and it will take a conditions
parameter. See:
http://api.rubyonrails.org/classes/ActiveRecord/Calculations/ClassMethods.html#M000969
If your condition is fairly simple and you can just use inject manually:
t = Ticket.find :all
s = t.inject{|sum,n| n.column_you_care_about == ''some_value'' ?
sum +
n.column_to_add : 0}
-Bill
John Tsombakos wrote:> Hello,
>
> This may just be my misunderstanding something, but I''m seeing
> something strange.
>
> I have a model, Ticket, that in the database table
''tickets'' has a
> field, let''s say ''seats''.
>
> I can do a Find and retrieve the items:
>
> t = Ticket.find :all
>
> Then do a sum to get the total seats:
> s = t.sum(&:seats)
>
> and that returns the correct sum.
>
> Playing in the console, I did:
> t.sum(&:seats)
>
> and while returning the correct sum, it also changed the
''t'' variable
> to be just the final item in the array. Is this correct? The sum is
> just doing an ''inject'', which I didn''t think
altered the original
> array, but maybe I''m wrong?
>
>
> And here''s a second question, say I want to use the found items,
but
> restrict the sum to a subset - total all seats that have been sold. I
> could do it by doing another find, but can I use .inject with a
> condition, so I don''t have to requery the database?
>
> Thanks!
>
> >
>
--
Sincerely,
William Pratt
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On Nov 8, 2007 11:53 AM, William Pratt <billp-YbheRAKfYF4eIZ0/mPfg9Q@public.gmane.org> wrote:> > Hmm, not sure on the console based sum findings, I don''t see the same > behavior. On your other question, the sum methods, etc all use > ActiveRecord::Calculations#calculate and it will take a conditions > parameter. See: > http://api.rubyonrails.org/classes/ActiveRecord/Calculations/ClassMethods.html#M000969 > > If your condition is fairly simple and you can just use inject manually: > > t = Ticket.find :all > > s = t.inject{|sum,n| n.column_you_care_about == ''some_value'' ? sum + > n.column_to_add : 0} > > -BillThanks. I think the weird console behavior may have just been my stupidity :) I think I was using the array inside the inject so it was just assigning to itself. Duh. I''m trying the simple inject, but for some reason it isn''t totaling the column. I''m using: s= t.inject(0) {|total,n| n.picked_up ? (total + n.seats) : 0} but it''s always coming out 0. (seats is a boolean, and I''m (for now) using sqlite, so the actual data is ''t'' or ''f'' - but looking at one record displays correctly - t[2].picked_up is true) I tried using n.picked_up? and n.picked_up == true Doing: t[2].picked_up ? "Y" : "N" correctly returns "Y" Thanks, jt --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On Nov 8, 2007 11:29 AM, John Tsombakos <tsom.rails-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> > Hello, > > This may just be my misunderstanding something, but I''m seeing > something strange. > > I have a model, Ticket, that in the database table ''tickets'' has a > field, let''s say ''seats''. > > I can do a Find and retrieve the items: > > t = Ticket.find :all > > Then do a sum to get the total seats: > s = t.sum(&:seats)It is *much* more efficient to use the AR calculation methods: s = Ticket.sum(:seats) The first one retrieves *all* of the rows and instantiates an AR object for each. The second issues a single query that returns one number.> > and that returns the correct sum. > > Playing in the console, I did: > t.sum(&:seats) > > and while returning the correct sum, it also changed the ''t'' variable > to be just the final item in the array. Is this correct? The sum is > just doing an ''inject'', which I didn''t think altered the original > array, but maybe I''m wrong?Dunno. I don''t see that behavior. The sum() method you''re using there is not the ActiveRecord::Base.sum method, but the Enumerable#sum method added by active support. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On Nov 8, 2007 12:16 PM, Bob Showalter <showaltb-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> > On Nov 8, 2007 11:29 AM, John Tsombakos <tsom.rails-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: > > > > Hello, > > > > This may just be my misunderstanding something, but I''m seeing > > something strange. > > > > I have a model, Ticket, that in the database table ''tickets'' has a > > field, let''s say ''seats''. > > > > I can do a Find and retrieve the items: > > > > t = Ticket.find :all > > > > Then do a sum to get the total seats: > > s = t.sum(&:seats) > > It is *much* more efficient to use the AR calculation methods: > > s = Ticket.sum(:seats) > > The first one retrieves *all* of the rows and instantiates an AR > object for each. The second issues a single query that returns one > number. >True, but I had already performed the Find that would then be passed along to my view, so I figured one less trip to the database - and if I also want a sum of seats not picked up, I''d then make yet another trip to the DB.> > > > and that returns the correct sum. > > > > Playing in the console, I did: > > t.sum(&:seats) > > > > and while returning the correct sum, it also changed the ''t'' variable > > to be just the final item in the array. Is this correct? The sum is > > just doing an ''inject'', which I didn''t think altered the original > > array, but maybe I''m wrong? > > Dunno. I don''t see that behavior. The sum() method you''re using there > is not the ActiveRecord::Base.sum method, but the Enumerable#sum > method added by active support.Yeah, I think that was just my dumb error. I also got the .inject method to work by doing instead: s= t.inject(0) {|total,n| total + (n.picked_up ? n.seats : 0)} --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On 8 Nov 2007, at 17:10, John Tsombakos wrote:> > s= t.inject(0) {|total,n| n.picked_up ? (total + n.seats) : 0} > > but it''s always coming out 0. (seats is a boolean, and I''m (for now) > using sqlite, so the actual data is ''t'' or ''f'' - but looking at one > record displays correctly - t[2].picked_up is true) I tried using > n.picked_up? and n.picked_up == truethe result of your block needs to be the running total - not the value of the individual term, ie n.picked_up ? (total + n.seats) : total Fred --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
On Nov 8, 2007 12:21 PM, Frederick Cheung <frederick.cheung-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:>> the result of your block needs to be the running total - not the value > of the individual term, ie > > n.picked_up ? (total + n.seats) : total > > FredAhhh.. thanks for the clarification.. I had a feeling I was missing something simple :) --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---
Sorry Tom, this was my fault. There way a typo in my original post. Glad you got it working. -Bill John Tsombakos wrote:> On Nov 8, 2007 12:21 PM, Frederick Cheung <frederick.cheung-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote: > > > >> the result of your block needs to be the running total - not the value >> of the individual term, ie >> >> n.picked_up ? (total + n.seats) : total >> >> Fred >> > > Ahhh.. thanks for the clarification.. I had a feeling I was missing > something simple :) > > > >-- Sincerely, William Pratt --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group. To post to this group, send email to rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org To unsubscribe from this group, send email to rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en -~----------~----~----~----~------~----~------~--~---