Scale and Precision of NSDecimalNumber value

Question

Let us suppose I have a variable v of type NSDecimalNumber

let v = 34.596904 in its own format.

I want to know the precision and scale of this number, not the default one. I did not find any function in the NSDecimalNumber class which gives these values or maybe someone would like to throw some light on how it works.

precision = 8
scale = 6

precision is count of significant digits in number and scale is count of significant digit after decimal

Answer 1

This extension will give you the specific value for your only example:

extension Decimal {
    var scale: Int {
        return -self.exponent
    }

    var precision: Int {
        return Int(floor(log10((self.significand as NSDecimalNumber).doubleValue)))+1
    }
}

Usage:

let v: NSDecimalNumber = NSDecimalNumber(string: "34.596904")

print("precision=\((v as Decimal).precision)") //->precision=8
print("scale=\((v as Decimal).scale)") //->scale=6

But I cannot be sure if this generates expected results in all cases you have in mind, as you have shown only one example...

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One more, in Swift, Decimal and NSDecimalNumber are easily bridgeable and you should better use Decimal as far as you can.