How to get the value of an NSDecimalNumber from NSDecimal?

Question

I have an array of objects, each object has an NSDecimalNumber, call it "size"

For each object in the array, I will subtract a recommended size, called rSize.

I then want to go into the resultant NSDecimalNumber and get the value of the delta, don't really care if it's positive or negative result.

I think I'm going to use the decimalNumber method which will return a NSDecimal struct, so the question is: which property within the struct will give me the value of the delta?

To rephrase: A NSDecimal represents an NSDecimalNumber, but which property of the NSDecimal struct holds the value?

Many thanks Rob

Answer 1

Your "delta" appears to be the absolute value of the difference between "rSize" and the item. In that case, you can perform the subtraction (item – rSize), and multiply it by -1 if it is negative entirely within NSDecimalNumber:

NSDecimalNumber *negativeOne = [NSDecimalNumber decimalNumberWithMantissa:1 
                                                                 exponent:0
                                                               isNegative:YES];
NSDecimalNumber *delta = [item decimalNumberBySubtracting:rSize];
if ([delta compare:[NSDecimalNumber zero]] == NSOrderedAscending) {
    delta = [delta decimalNumberByMultiplyingBy:negativeOne];
}

Then use the -compare: selector on the resulting delta objects to sort your array of objects.