What's the best way to convert an inputed numeric string to a NSDecimalNumber, considering the number of fraction digits for a given locale?

Question

Is there an API for this? Or maybe a better way of doing it?

Here's what I'm trying to acomplish:

In is a numeric string. Out, is a NSDecimalNumber

// this one is for US:

in:   1  out: 0.01
in:  12  out: 0.12
in: 123  out: 1.12

// a diferent locale might have a diferent maximumFractionDigits, like 1

in:   1  out:  0.1
in:  12  out:  1.2
in: 123  out: 12.3

// other locales might have 0, or 3 fraction digits.

Here's how I have it:

// Clear leading zeros
NSNumber *number = [formatter numberFromString:numericString];
numericString = [formatter stringFromNumber:number];

if (maximumFractionDigits == 0) {
    return [NSDecimalNumber decimalNumberWithString:numericString];
}

else if (numericString.length <= _currencyFormatter.maximumFractionDigits) {

    NSString *zeros = @"";

    for (NSInteger i = numericString.length; i < maximumFractionDigits ; i++) {
        zeros = [zeros stringByAppendingString:@"0"];
    }

    return [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"0.%@%@",zeros,numericString]];

} else {


    NSString *decimalString = [NSString stringWithFormat:@"%@.%@",
                            [_rateInput substringToIndex:numericString.length - maximumFractionDigits],
                          [_rateInput substringFromIndex:numericString.length - maximumFractionDigits]];

    return [NSDecimalNumber decimalNumberWithString: decimalString];

}

While this does seem to work, I was wondering if there is an API for this, or a more simple, less error prone way of doing it?