How can I determine if a Cocoa NSNumber represents NaN (not a number)?
This emerges, for example, when I parse a string that has an invalid (non-numeric) contents.
Determine if NSNumber is NaN
user_79
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9 Answers
So, I found out that the class property [NSDecimalNumber notANumber] is just for this purpose. In some languages NaN != NaN, but this isn't the case in Cocoa.
As Mike Abdullah says, the natural way to represent a NaN in Cocoa is with nil, but [NSNumber numberWithDouble:NAN] does return a valid object. There is no NSNumber-specific way of detecting this, but the general way, isnan([foo doubleValue]), works. If you don’t like functions, you can stick it in a category.
There isn't really such an object for NSNumber since if it's not a number, then, well, it's not an NSNumber. It's more usual to use a nil object to represent this.
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