Nate Thorn Nate Thorn - 1 day ago 4
Objective-C Question

Rounding NSDecimalNumber

I'm having the hardest time figuring out something that seems like it should be very simple. I need to accurately round an NSDecimalNumber to a particular number of decimal places (determined at runtime.) So far as I can tell, I have two options, neither of which I like.


  1. Convert to a float, and use C rounding functions: I don't like this because accuracy matters in this case. Floats can't always accurately represent decimal numbers, and this could cause problems.

  2. Convert to a string using NSNumberFormatter and then convert back: I don't like this one because it just seems ugly and inefficient.



Is there another way that I've missed? There has got to be an easy way to do rounding of NSDecimalNumbers, but I can't seem to figure out for the life of me what it is.

Answer

You simply call decimalNumberByRoundingAccordingToBehavior:with the desired NSDecimalNumberBehaviors protocol. See the NSDecimalNumberBehaviors reference in the dev docs.

Update: See http://www.cimgf.com/2008/04/23/cocoa-tutorial-dont-be-lazy-with-nsdecimalnumber-like-me/

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