Dealing with money

Hello all,

I’ve had a look at the Money gem and some others but I think they may be overkill for what I want. Some advice would be nice.

I have a site where people pledge some money to an account. The amounts could come from all over the world and I want the user to be able to mark the currency that they’re pledging in their currency.

I was thinking of having a table of currencies (symbols etc) and just allowing the free selection of those. Store the amounts as decimal (no calculations are being done on the values) along with the currency ID.

The formatting of the amounts will be ###,###.## (it doesn’t have to be locale specific). I also wanted to have a breakdown of the different currencies that go towards making the total …

55.00 GBP

175.00 USD

3000.00 CAN

Ants Pants wrote in post #983192:

The formatting of the amounts will be ###,###.## (it doesn't have to be
locale specific). I also wanted to have a breakdown of the different
currencies that go towards making the total ....

   55.00 GBP
175.00 USD
3000.00 CAN

How does this total make any sense? The number 3230.00 is a meaningless
value without the currency unit and exchange rate.

I have looked around for currencies in easily downloadable format
(JSON/YAML/XML) but haven't found any good resources. Does anyone know

Downloadable format for what? Do you mean currency exchange rates?
Wouldn't you need to know that? If someone were to pledge 55.00 GBP, do
you plan on converting that into a common local currency at the time of
the pledge? Or, do you plan on converting that pledge to a local
currency at the time the final donation is processed, based on the
exchange rate at that time?

What I'm saying is that not only does it not make sense to sum the
pledges, without first converting them to a common unit, but the
conversion factor between the units changes over time.


I think you're just looking for a simple database of known currency
labels. I don't know of anything off the top of my head, but if you
check out Bloomberg's currency conversion system:

You can view source and probably rip out the currency labels from the
select lists.

To re-iterate Robert's point above, if it's the conversion you're
looking to do, I'd really recommend looking at a subscription-based
web service that your application can "talk to" in order to perform
the conversions, because global currency exchange rates fluctuate
every day, sometimes multiple times per day. It would be a NIGHTMARE
keeping up with that yourself, so a third party to do the conversions
for you would be a real life-saver! Unfortunately I can't make any
specific recommendations for that kind of service, but I'm sure there
are plenty of companies out there who you could work with.

I hope this helps you out. Good luck!

Thanks for your replies.

To answer a few of your questions …

In my example, I gave a total of all amounts pledged. This of course does not make sense and I’m now not even sure why I wrote it (it was the last thing I wrote before going to lala land). I have no intention of doing that.

What I will do is, give totals for each currency used (which is what I wanted to get over in my first mail).

As I said before, nothing complicated is happening with this. It’s just a simple pledge and people will make the actual payment on another site. There could be a lengthy time lapse between when the pledge was made and when payment was made. It’s just a guide. That’s all. Hence, actual exchange rates are not needed.

So I guess my question is; is it worth using the Money gem or is it better to store a few major currencies in a table, give the user the selection and then just add a simple general formatting rule.

I prefer the second option but I’m open to change my mind.

I will check out thank you Phoenix Rising.

Again, thank you.

If you can live with once per day updates, not closing rates or anything specific, then this is a great resource:

All it sets out to do is document the difference between currencies that day, nothing else.

I built a currency converter many years ago based on this file, and it's just CSV so it's very easy to parse and use. Since it's not SAAS and it's static (not analytical) I don't think they pay too much attention to the traffic numbers. My converter would just check to see if the current cached copy was out of date, and get a new one if needed, and then everything else was parsed into a hash and used to drive the conversions from a base currency to a target.