ExchangeRateProvider method parameters

[chsagynov]

In the ExchangeRateProvider interface, we have a getExchangeRate(string $sourceCurrencyCode, string $targetCurrencyCode) method. Can we change the parameter type to getExchangeRate(Currency $sourceCurrency, Currency $targetCurrency)? I'm guessing most databases use an int ID rather than a CODE string. In our case, we need to add some unnecessary relationships when fetching from the database. Also, the internal database may use an internal incremental ID instead of the ISO ID.

[mklepaczewski]

While we are at it, I think the method:

• should accept DateTime $date as exchange rate depends not only on the currencies but also on the date of the exchange. It should be up to the implementing class to decide how to treat the $date,
• it should return an object CurrencyExchangeRate with date, source currency, target currency and the exchange rate.