Grouping an array and get sum

Question

I have the following setup.

Invoice has_many Jobs has_many Tasks belongs_to user

I want to get all Users for an Invoice that have tasks and sum up their quantities

class Invoice < ActiveRecord::Base
  has_many :jobs
end

class Job < ActiveRecord::Base
  belongs_to :invoice 
  has_many :tasks      
end

class Task < ActiveRecord::Base
  belongs_to :job                   
  belongs_to :user     
end     

Here is what I got

@invoice = Invoice.find(params[:id])
jobs = @invoice.jobs.joins(:tasks)
        .select('tasks.user_id, (sum(tasks.quantity)*jobs.price) as total')
        .group('tasks.user_id, jobs.id')
        .order('tasks.user_id')

I get this, which is close to what I want

- !ruby/object:Job
  attributes:
    user_id: '1'
    total: '60.00'
- !ruby/object:Job
  attributes:
    user_id: '1'
    total: '50.00'
- !ruby/object:Job
  attributes:
    user_id: '2'
    total: '120.00'
- !ruby/object:Job
  attributes:
    user_id: '2'
    total: '100.00'  

How can I group this by user_id and sum up the total so that I have something like this?

user_id: 1
total: 110
user_id: 2
total: 220

Answer 1

thansk for your answers.

I managed to solve this with

user_totals = jobs.to_a.group_by(&:user_id).map{ |user_id,jobs| {:user_id => user_id.to_i, :total => jobs.sum {|j| j.total.to_f} }} 
=> [{:user_id=>1, :total=>110.0}, {:user_id=>2, :total=>220.0}]