How to sum returned rows from a model using inject?

rubyonrails-talk
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,

3

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

4

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

5

Hi,

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

Regards,

Craig

6

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