Rails - Jul 2009 - How to sum returned rows from a model using inject?

Here''s my current loop:

update_total = model.find(:all)
update_total.each do |row|

  val = ((row.totoff + row.rushoff + row.passoff + row.scoroff +
row.rzonoff + row.fumlost + row.passhint + row.tolost + row.sacksall +
row.tackflossall + row.passeff + row.firdwns + row.thrdwncon +
row.fthdwncon)/14.0).round_to(4)

  row.totals = val
  row.save
  puts "Team = #{row.team.name} and total val = #{val}."
end

This of course looks sloppy.  I thought I could use something similar:

val = row.inject(0){|sum,item| sum + item}

.. but I can''t figure out how to use this without it adding specific
columns, namely..

team_id, totals, compiled_on, created_at, updated_at

.. these 5 columns should be exempt from sums..

It''s not overly important and I can work around it.  I guess I just
want
to keep my code as clean as possible and didn''t know if there is a more
preferred way to sum up a row''s totals in rails..

Thanks.
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Älphä Blüë wrote:
[...]
> .. but I can''t figure out how to use this without it adding
specific
> columns, namely..
> 
> team_id, totals, compiled_on, created_at, updated_at
> 
> .. these 5 columns should be exempt from sums.
How about using [:column1, :column2, ...] - [:team_id, :totals, ...] ? 
Remember, Array#- actually works in Ruby.

Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
-- 
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Thanks Marnen,

I had a feeling it was going to be simpler than I was trying to make it 
out to be.  Appreciate the info..

I think I''ve learned more about arrays and hashes in ruby this week
over
anything, which is a good thing.

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On Sat, Jul 18, 2009 at 12:50 PM, Älphä Blüë <
rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org> wrote:
>
> Here''s my current loop:
>
> update_total = model.find(:all)
> update_total.each do |row|
>
>  val = ((row.totoff + row.rushoff + row.passoff + row.scoroff +
> row.rzonoff + row.fumlost + row.passhint + row.tolost + row.sacksall +
> row.tackflossall + row.passeff + row.firdwns + row.thrdwncon +
> row.fthdwncon)/14.0).round_to(4)

Instead of querying the model for all of this data, I recommend
encapsulating this calculation in the model itself. Also, I''d give
meaningful names to 14.0 and 4 to clearly communicate what purpose they
serve in the calculation.

Then your loop could be:

Model.all.each do |model|
  model.recalculate_total
  model.save!
  puts ...
end


-- 
Craig Demyanovich
Mutually Human Software
http://mutuallyhuman.com

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Thanks for the advice Craig.  I''m always looking for better way to do 
things.  Much appreciated.

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Hi Craig,

Did you mean something like this?

Both methods are in the model..

def recalculate_totals(row)
  fields = 5.0
  row.totals = ((row.kickret + row.puntret + row.netpunt + 
row.kickretdef + row.puntretdef) / fields).round_to(4)
end

model.compiled_this_week.all.each do |row|
  row.recalculate_totals(row)
  row.save!
  puts "Team = #{row.team.name} and total val = #{row.totals}."
end

-- 
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Älphä Blüë wrote:
> Hi Craig,
> 
> Did you mean something like this?
> 
> Both methods are in the model..
> 
> def recalculate_totals(row)
[...]

You don''t need an argument on this method, since the row is already 
accessible as self.

Best,
--
Marnen Laibow-Koser
http://www.marnen.org
marnen-sbuyVjPbboAdnm+yROfE0A@public.gmane.org
-- 
Posted via http://www.ruby-forum.com/.

Hi,
Yes, and Marnen''s observation in a later message about not needing to
pass
row is spot on.

Regards,
Craig


-- 
Craig Demyanovich
Mutually Human Software
http://mutuallyhuman.com

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Thanks guys.

I changed it to:

def recalculate_totals
  fields = 5.0
  self.totals = ((self.kickret + self.puntret + self.netpunt + 
self.kickretdef + self.puntretdef) / fields).round_to(4)
end

and..

model.compiled_this_week.all.each do |row|
  row.recalculate_totals
  row.save!
  puts "Team = #{row.team.name} and total val = #{row.totals}."
end

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