a custom type that defines a cast method which will branch on the not-completely-bulletproof heuristic of assuming Numeric values are already in cents and any other values will need to be converted from dollars.

cents.rb

class Cents < ActiveRecord::Type::Integer
  def cast(value)
    return super if value.is_a?(Numeric)

    price_in_dollars = value.to_s.delete("$").to_d
    price_in_cents = (price_in_dollars * 100).to_i
    super(price_in_cents)
  end

  def self.dollarize(value)
    price_in_cents = value.to_d
    "$#{"%.2f" % (price_in_cents / 100)}"
  end
end


# Globally register:
ActiveModel::Type.register(:cents, Cents)

# usage:
attribute :max_price, :cents, default: -> { 100_00 }