Convert between a C double and Cocoa's NSDecimalNumber?

Question

I'm converting an algorithm I wrote in Java to Objective-C. In java the BigDecimal class handles base-10 numbers and can take the primitive double as a constructor arg. In Cocoa's NSDecimalNumber class, however, there is no direct way to construct an instance using a primitive double.

Currently I'm using this (smelly) hack:

    [NSDecimalNumber decimalNumberWithString:[NSString stringWithFormat:@"%1.38f", number]];

Is there a better way?

Answer 1

NSNumber, the superclass of NSDecimalNumber, has a +numberWithDouble: method. That's what you want.

Answer 2

[NSDecimalNumber numberWithDouble:myDouble]

Answer 3

In other posts I'm finding info that using the NSNumber methods with NSDecimalNumber either will return NSNumber, or will return NSDecimalNumber but that's not what the spec says it should so it may be considered a bug and change in the future. Er something like that.

Answer 4

I've found the way to get this to work, and to dismiss the warning is like this.

    NSNumber *temp = [NSNumber numberWithDouble:self.hourlyRate];
    myDecimal = [NSDecimalNumber decimalNumberWithDecimal:[temp decimalValue]]; 

It gets rid of the warning, albeit being two lines instead of one.