Convert NSNumber to NSDecimalNumber

Question

I realize that NSDecimalNumber inherits from NSNumber.

However, I am struggling to figure out how I can init an NSDecimalNumber from an NSNumber or how to convert an NSNumber to an NSDecimalNumber.

I have tried

NSDecimalNumber* d = [aNumber copy];

where aNumber is an NSNumber object to no avail.

Am I missing something?

Thanks.

As an aside, `[NSNumber copy]` is never going to return a `NSDecimalNumber`… I’m only aware of conversions via `NSDecimal` (like in the answers below) or via `NSString`. — jbg, Sep 07 '14 at 02:52

score 85 · Accepted Answer · answered Feb 05 '14 at 05:57

85

You can do:

NSDecimalNumber *decNum = [NSDecimalNumber decimalNumberWithDecimal:[aNumber decimalValue]];

answered Feb 05 '14 at 05:57

rmaddy

Only problem is that passing an NSNumber with value of 2e+34 ends up with decNum of 2 and 34 zeros. would like it to maintain the same mantissa and exponent. – Michael Rivers Feb 05 '14 at 06:21
1

`2e+34` is 2 with 34 zeros. Those are the same number expressed in two different ways. – rmaddy Feb 05 '14 at 06:33

Eike · Answer 2 · 2015-10-26T09:29:35.123

21

So:

NSNumber * number = [NSNumber numberWithInt:10];
NSDecimalNumber *d = [NSDecimalNumber decimalNumberWithDecimal:[number decimalValue]];

And in Swift

let number = NSNumber(int: 10)
let dec = NSDecimalNumber(decimal: number.decimalValue)

edited Oct 26 '15 at 09:29

answered Feb 05 '14 at 05:53

Eike

The 2nd one isn't valid (and in both cases `d` needs to be a pointer). – rmaddy Feb 05 '14 at 05:58
@rmaddy what are you talking about? – pronebird Oct 27 '15 at 15:37
@Andy The answer has been edited twice (as of this comment) since my original comment. Look at the edit history to see what the answer looked like at the time of my comment. – rmaddy Oct 27 '15 at 15:39

2 Answers2