Problems with money-rails in Ruby

I was following a tutorial to use money-rails in a new project.

Here is my migration file:

class AddFieldsToPlan < ActiveRecord::Migration[5.1]
  def change
    add_column :plans, :payment_gateway_plan_identifier, :string
    add_column :plans, :price, :integer
    add_column :plans, :interval, :integer
    add_column :plans, :interval_count,:integer
    add_column :plans, :status,:integer
    remove_column :plans, :amount
    remove_column :plans, :payment_frequency

  end
end

And my model:

class Plan < ApplicationRecord

  enum status: {inactive: 0, active: 1}
  enum interval: {day: 0, week: 1, month: 2, year: 3}

  monetize :price_cents

  def end_date_from(date = nil)
    date ||= Date.current.to_date
    interval_count.send(interval).from_now(date)
  end


end

I read all the API specification of money-rails but doesnt understand well I guess.

If I run the rails console, and do a Plan.last.price it shows me this error:

.3.4 :001 > Plan.last.price
  Plan Load (2.6ms)  SELECT  "plans".* FROM "plans" ORDER BY "plans"."id" DESC LIMIT $1  [["LIMIT", 1]]
NoMethodError: undefined method `price_cents' for #<Plan:0x007f8ca807f8f0>
Did you mean?  price_cents=
        from (irb):1

What Im doing wrong here? How can I set up a value for this price attribute?

Thanks

Look at the tutorial for `money-rails' you'll see the migration they recommend is

add_monetize :products, :price # Rails 4x and above

That actually creates an integer field called price_cents in the model.

You need another migration to remove price and then use the above line to add the price_cents to the table.