parsing string into different kind of number string - objective-c

Question

I have a string called realEstateWorth with a value of $12,000,000.
I need this same string to remain a string but for any number (such as the one above) to be displayed as $12 MILLION or $6 MILLION. The point is it needs the words "MILLION" to come after the number.
I know there is nsNumberFormatter that can convert strings into numbers and vice versa but can it do what I need?
If anyone has any ideas or suggestions, it would be much appreciated.
Thank you!

Answer 1

So as I see it, you have two problems:
You have a string representation of something that's actually a number
You (potentially) have a number that you want formatted as a string
So, problem #1:
To convert a string into a number, you use an NSNumberFormatter. You've got a pretty simple case:
NSNumberFormatter *f = [[NSNumberFormatter alloc] init];
[f setNumberStyle:NSNumberFormatterCurrencyStyle];
NSNumber *n = [f numberFromString:#"$12,000,000"];
// n is 12000000
That was easy! Now problem #2:
This is trickier, because you want a mixed spell-out style. You could consider using an NSNumberFormatter again, but it's not quite right:
[f setNumberStyle:NSNumberFormatterSpellOutStyle];
NSString *s = [f stringFromNumber:n];
// s is "twelve million"
So, we're closer. At this point, you could perhaps maybe do something like:
NSInteger numberOfMillions = [n integerValue] / 1000000;
if (numberOfMillions > 0) {
NSNumber *millions = [NSNumber numberWithInteger:numberOfMillions];
NSString *numberOfMillionsString = [f stringFromNumber:millions]; // "twelve"
[f setNumberStyle:NSNumberFormatterCurrencyStyle];
NSString *formattedMillions = [f stringFromNumber:millions]; // "$12.00"
if ([s hasPrefix:numberOfMillionsString]) {
// replace "twelve" with "$12.00"
s = [s stringByReplacingCharactersInRange:NSMakeRange(0, [numberOfMillionsString length]) withString:formattedMillions];
// if this all works, s should be "$12.00 million"
// you can use the -setMaximumFractionDigits: method on NSNumberFormatter to fiddle with the ".00" bit
}
}
However
I don't know how well this would work in anything other than english. CAVEAT IMPLEMENTOR

Answer 2

Worst case scenario, you could implement a category on NSString to implement the behaviour you want.
In the method that you would do in that category you could take an NSNumberFormatter to bring that string to a number and by doing some modulo operation you could define if you need the word Million, or Billion, etc. and put back a string with the modulo for Million or other way you need it to be.
That way you could just call that method on your NSString like this :
NSString *humanReadable = [realEstateWorth myCustomMethodFromMyCategory];
And also.
NSString are immutable, so you can't change it unless you assign a new one to your variable.

Answer 3

I'd recommend storing this value as an NSNumber or a float. Then you could have a method to generate an NSString to display it like:
- (NSString*)numberToCurrencyString:(float)num
{
NSString *postfix = #"";
if (num > 1000000000)
{
num = num / 1000000000;
postfix = #" Billion";
}
else if (num > 1000000)
{
num = num / 1000000;
postfix = #" Million";
}
NSString *currencyString = [NSString stringWithFormat:#"%.0f%#", num, postfix];
return currencyString;
}
Note: Your question states that your input needs to remain a string. That's fine. So you'd need to 1.) first parse the number out of the string and 2.) then reconvert it to a string from a number. I've shown how to do step 2 of this process.