Add values from a column with Ruby

Question

Hello I’m starting my studies with Ruby On Rails, and I’m making an application that manages expenses. Well what I need to do sum up all the expenses of the "value" column and show in the view.

I’m trying the following on Activerecord

def total
    divida.sum("valor * ")
end

Would that be the right way? how do I show in the view?

Thanks for your attention!

Answer 1

You can do as quoted in the other answer, only never call a model method in a view, because model does not communicate with view, and that is one of the fundamentals of MVC. You can call this method in your control, reference in a variable and use it in your view

in his model:

class Payment
  def self.total
    self.sum(:value)
  end
end

on your controller:

class PaymentsController < ApplicationController
  def index
    @sum_of_payments = Payment.total
  end
end

in your view on app/Payments/index.html.erb:

<%= @sum_of_payments %>

ps: avoid writing code in Portuguese, and even worse, mix English with Portuguese.

Answer 2

The class that represents your model may contain a class method that calculates the sum of all debt values. I’m guessing there’s a table dividas in your database, which contains a column valor.

class Divida < ActiveRecord::Base
  def self.total
    self.sum(:valor)
  end
end

Then in your view (for example the file app/views/divida/index.html.erb ), you can call Divida.total that will return the total of all debts.