iOS Currency input field - ios

Question

I would like to have a currency input field in my app where the user can either include the currency symbol (as appropriate for their locale), or not, as they please.
I have a text field set up and I am storing the value in a NSDecimalNumber (which I understand is the recommended way to store currency).
The following code will get me from an NSDecimalNumber to a formatted currency string:
[NSNumberFormatter localizedStringFromNumber:currencyValue numberStyle:NSNumberFormatterCurrencyStyle]
But I can't find a way to do the reverse of that. i.e., take the string that the user has typed into my text field and convert it (if possible) into an NSDecimalNumber. Keeping in mind that the currency symbol may be there (because it came from the function above) or not (because the user didn't bother to type the currency symbol).
What am I missing?
If I can't figure this out I will just not accept any currency symbol at all (i.e., just parse it using the code below). But it seems better to allow the currency symbol.
[NSDecimalNumber decimalNumberWithString:currencyString locale:[NSLocale currentLocale]]
I have the feeling I am missing something. What's the right way to convert back and forth between a localized currency string and an NSDecimalNumber?

Answer 1

If you get an instance of an NSNumberFormatter (instead of using the static method call) you can use the NSNumberFormatter's "stringFromNumber" method to format the currency string and use "numberFromString" to parse that string back into a number.
https://developer.apple.com/library/mac/documentation/cocoa/reference/foundation/Classes/NSNumberFormatter_Class/Reference/Reference.html

Answer 2

If you are sure that the currency symbol, if it exists, will be at the beginning of the string, then you can just use this (string is the NSString that the user enters and number is the NSDecimalNumber that represents the value of the currency)
NSDecimalNumber *number;
if([string hasPrefix:#"0"] || [string hasPrefix:#"1"] || [string hasPrefix:#"2"] || [string hasPrefix:#"3"] || [string hasPrefix:#"4"] || [string hasPrefix:#"5"] || [string hasPrefix:#"6"] || [string hasPrefix:#"7"] || [string hasPrefix:#"8"] || [string hasPrefix:#"9"]) {
// The string does not contain a currency symbol in the beginning so we can just assign that to a NSDecimalNumber
number = [NSDecimalNumber decimalNumberWithString:string];
}
else {
// The string contains a currency symbol at the beginning and we will assign the currency symbol to the currencySymbol variable
NSString *currencySymbol;
currencySymbol = [string substringWithRange:NSMakeRange(0,1)];
number = [NSDecimalNumber decimalNumberWithString:[string stringByReplacingCharactersInRange:NSMakeRange(0,1) withString:#""];
}

Answer 3

This should do the trick:
NSNumberFormatter *currencyFormatter = [[NSNumberFormatter alloc] init];
[currencyFormatter setNumberStyle:NSNumberFormatterCurrencyStyle];
[currencyFormatter setLenient:YES];
NSString* input = #"$3,456.78";
NSNumber *number = [currencyFormatter numberFromString:input];
NSDecimalNumber *price = [NSDecimalNumber decimalNumberWithDecimal:[number decimalValue]];