money representation in mongoid

Question

How should I work with Money with MongoID? Should I configure it as BigDecimal? And at rails level? For ActiveRecord we have something called Money, but AFAIK it just supports AR

dm is right. Never use floating point numbers to represent money (like floats, doubles). This will make a lot of butthurt. You will lose cents during representation. For example 10.2 may be represented like 10.19999(9). During rounding and different arithmetic operations you will get increasing error. [Why not to use double to represent currency](http://stackoverflow.com/questions/3730019/why-not-use-double-or-float-to-represent-currency/3730040#3730040) — Dao, Apr 13 '11 at 18:43

Brian Armstrong · Answer 1 · 2012-02-21T06:44:25.250

I ran into this also. Unfortunately BigDecimal stores in Mongodb as a string, so it won't let you sum, sort, etc on it like a float or int.

Integer seem to be the way to go storing the value in cents, possibly using the Money gem to abstract it a bit: https://github.com/RubyMoney/money

Mongo stores the int using 64 bits on most modern machines I think so there is not much risk of needing a larger amount even in cents. It looks like you can store between −9,223,372,036,854,775,808 and 9,223,372,036,854,775,807 cents, so take off two decimal places to get your min/max value in dollars.

http://en.wikipedia.org/wiki/Integer_(computer_science)

score 3 · Accepted Answer · answered Sep 28 '10 at 20:25

3

MongoDB stores numbers in various BSON data types (int, long int, double). I recommend you store money as cents (if U.S. currency) and use the long int datatype.

answered Sep 28 '10 at 20:25

dm.

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score 2 · Answer 3 · answered Feb 21 '13 at 20:00

If you like the money gem you can store it as a Money type.

An example: https://gist.github.com/michaelkoper/5007636

It stores the money as an array [cents, currency]

class Product
   include Mongoid::Document

  field :price,    type: Money
end

product = Product.new(:price => Money.new(1000, 'EUR'))
product.price.format
# => "€10.00"

score 0 · Answer 4 · answered Dec 25 '12 at 11:27

0

I recommend you try money-rails as an alternative. https://github.com/RubyMoney/money-rails It is pretty well maintained and works with mongoid too!

answered Dec 25 '12 at 11:27

P Pramod Nair

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I have an issue with it. I'm currently using: money-rails v1.12 rails v6 mongoid v7 I would like to set the default currency to be used by each model instance. I have set the field in my model like below `field :price, type: Money, with_model_currency: :currency` But when I try to create or fetch records I get this error `Mongoid::Errors::InvalidFieldOption` `message: Invalid option :with_model_currency provided for field :price.` How do I use the `with_model_currency` option in a rails mongoid application? How else can I handle money in a rails mongoid application? – Jatto_abdul Apr 29 '20 at 21:36

money representation in mongoid

4 Answers4