How to modify number using NSNumberFormatter? [closed]

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Closed 8 years ago.

I have values such as:

5.1M (5100000)
80M (80000000)
300.5M (300500000)

5K (5000)
2000K (2000000)
200.5K (200500)

(Values I need to turn them into are in parenthesis behind the numbers).

Basically, a number can have a decimal point or no decimal point, can end with K (for thousand) or M (for million), but ONLY when it's a whole number (i.e. 0.5M needs to be 500000; no commas).

I also need to be able to convert numbers back to their original form.

How do I do this, and what's the best way to do it?

Answer 1

So you're saying you have an NSString that starts with a number and ends with K or M? And you want to see what it consists of, and convert it to an actual numeric value? This is a job for NSScanner.

Though, to be quite honest, NSScanner was around long before regular expressions became available in Objective-C; nowadays I might just use NSRegularExpression.

Or, if you know for a fact that it really is a number followed by K or M, then you don't even have to do that. Just pull the last character off the end. That's the K or the M and you now know which it is. And what's left is a numeric string and you can just convert it to a number.

Pseudocode (not tested):

NSString* s = @"5.1M";
NSUInteger len = s.length;
NSString* numPart = [s substringToIndex: len-2];
NSString* unitPart = [s substringFromIndex: len-1];
int multiplier = 1000;
if ([unitPart isEqualToString: @"M"])
    multiplier = 1000000;
float result = numPart.floatValue * multiplier;

Answer 2

A while back I wrote and open-sourced a custom NSNumberFormatter called SQSMetricFormatter (https://github.com/shultzc/SQSMetricFormatter) that, well, formats numbers using metric prefixes.

It might do what you need, or at least provide a jumping off point for implementing your own solution.