Rails Migration changing column to use Postgres arrays

Question

I am trying to change a column in my database so that it can use the Postgres array data type. Currently the table column is of type string.

I am using the following

Answer 1

Using Rails 4.2 on postgresql 9.4 with a down and a up, base on lrrthomas response. Note: your starting column should have a default of nil

class ChangeEmailAndNumberColumnForContact < ActiveRecord::Migration
  def up
    change_column :contacts, :mobile_number, :text, array: true, default: [], using: "(string_to_array(mobile_number, ','))"
    change_column :contacts, :email, :text, array: true, default: [], using: "(string_to_array(email, ','))"
  end

  def down
    change_column :contacts, :mobile_number, :text, array: false, default: nil, using: "(array_to_string(mobile_number, ','))"
    change_column :contacts, :email, :text, array: false, default: nil, using: "(array_to_string(email, ','))"
  end
end