Formatting decimal places with unknown number

Question

I\'m printing out a number whose value I don\'t know. In most cases the number is whole or has a trailing .5. In some cases the number ends in .25 or .75, and very rarely th

Answer 1

If you want to print a floating point number to 3 decimal places, you can use String(format: "%.3f"). This will round, so 0.10000001 becomes 0.100, 0.1009 becomes 0.101 etc.

But it sounds like you don’t want the trailing zeros, so you might want to trim them off. (is there a way to do this with format? edit: yes, g as @simons points out)

Finally, this really shouldn’t be a class function since it’s operating on primitive types. Better to either make it a free function, or perhaps extend Double/Float:

extension Double {
    func toString(#decimalPlaces: Int)->String {
        return String(format: "%.\(decimalPlaces)g", self)
    }
}

let number = -0.3009
number.toString(decimalPlaces: 3)  // -0.301