I use NSNumberFormatter to format currencies in a localized way, and it works fine. But I want to override this and give the user the option to override the number of digits after the decimal separator.

How can I find out the number of digits the NSNumberFormatter will use for a certain currency? I have looked in the NSLocale object, but none of the keys tell me this.

NSString * const NSLocaleIdentifier;
NSString * const NSLocaleLanguageCode;
NSString * const NSLocaleCountryCode;
NSString * const NSLocaleScriptCode;
NSString * const NSLocaleVariantCode;
NSString * const NSLocaleExemplarCharacterSet;
NSString * const NSLocaleCalendar;
NSString * const NSLocaleCollationIdentifier;
NSString * const NSLocaleUsesMetricSystem;
NSString * const NSLocaleMeasurementSystem;
NSString * const NSLocaleDecimalSeparator;
NSString * const NSLocaleGroupingSeparator;
NSString * const NSLocaleCurrencySymbol;
NSString * const NSLocaleCurrencyCode;
NSString * const NSLocaleCollatorIdentifier;
NSString * const NSLocaleQuotationBeginDelimiterKey;
NSString * const NSLocaleQuotationEndDelimiterKey;
NSString * const NSLocaleAlternateQuotationBeginDelimiterKey;
NSString * const NSLocaleAlternateQuotationEndDelimiterKey;

How can I find out the correct number of decimals for a currency like the NSNumberFormatter seems to know?