Data type for currency using Mongoid

You might probably want to have a look at the Money gem.

The way it works, is to represent money amounts in cents and use integers.You can follow this way and store your data as integer so that you don't need to deal with Float precision.

What Simone Says.

I just inserted the money gem in my project and you can store it as a Money type as well.

class Product  include Mongoid::Document  field :price,    type: MoneyendMoney.class_eval do  # Converts an object of this instance into a database friendly value.  def mongoize    [cents, currency.to_s]  end  class << self    # Get the object as it was stored in the database, and instantiate    # this custom class from it.    def demongoize(object)      cur = object[1] || Money.default_currency      Money.new(object[0], cur)    end    # Takes any possible object and converts it to how it would be    # stored in the database.    def mongoize(object)      case object      when Money        object.mongoize      else object      end    end    # Converts the object that was supplied to a criteria and converts it    # into a database friendly form.    def evolve(object)      case object      when Money then object.mongoize      else object      end    end  endend   

Floats would work fine for currency if you didn't actually use the fraction part, that is, if you only stored prescaled integral values. Floats store integers and perform integer ops exactly.

Of course, at that point, you might as well use integers.