How to sum returned rows from a model using inject?

Rails
1

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.

2

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
[email protected]

3

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.

4

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

5

On Sat, Jul 18, 2009 at 12:50 PM, Älphä Blüë <
[email protected]> 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 D.
Mutually Human Software

6

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
[email protected]

7

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

8

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

Regards,
Craig

–
Craig D.
Mutually Human Software

9

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