Question

I am new to rails. I understand instance variables in controller getting data from the model and displaying to the view. How can I send instance variables to the model though? I want to run computations on the variable and send it back to the view updated by the model.

Answer 1

You should just pass controller instance vars to the model as method arguments. Here’s an example:

# model
class MyModel < ActiveRecord::Base
  def run_computations var1, var2
    # perform complex computations
    [var1 * 2, var2 * 3]
  end
end


# controller
class MyController < ApplicationController
  def my_action
    @var1 = 10
    @var2 = 20

    @var1, @var2 = MyModel.run_computations @var1, @var2
    # MyModel.run_computations returns an array. The line above is a shortcut for
    #   picking the array apart. It is equivalent to this
    # arr = MyModel.run_computations @var1, @var2
    # @var1 = arr[0]
    # @var2 = arr[1]
  end
end