default_currency misconception

[adamduffy]

when doing multi-currency business, it is very dangerous to not know for sure and assume a "default currency". i.e. storing {amount: 1, currency: nil} and assuming that's USD. USA is not the center of the universe, and neither is any other country/currency.

ex:

Money.from_amount(1)
=> #<Money fractional:100 currency:USD>

i have a hard time thinking of a use case where not knowing and guessing is better than knowing for sure. i can think of use cases for the idea of a "preferred currency", which could be used for comparisons, but never as a fallback for unknown.

I am curious if there are use cases for the dangerous assumption, or if this is intended to be used more as a "preferred" currency.

i do see that Money.default_currency=nil is a good workaround. perhaps this should be the default instead of USD?

[antstorm]

@adamduffy I guess the reason behind default_currency in the first place is for single-currency apps where everything is expected to be in one currency. But if anything it's just a shorthand that is potentially dangerous as you've noted.

I like the idea of switching the default to nil forcing people to pick one at their own risk. As it's a breaking change we can include it in the upcoming v7 release. Would you be interested in opening a PR?

[thealiilman]

Hey @antstorm, I stumbled upon this issue recently. There doesn't seem to be any work being done on this, and I thought this is a nice issue for me to get my hands dirty with contributing to open source. 🤓

I misunderstood the exchange above between you and Adam, hence the initial PR was closed. I had thought it was to force the developer to set the default value, and not initialising a Money object with nil as its currency.

I have created a PR for this change. 👌

[antstorm]

#868 is now merged and will get included in v7 release