user3925713 user3925713 - 7 months ago 26
Swift Question

Getting the decimal part of a double in Swift

I'm trying to separate the decimal and integer parts of a double in swift. I've tried a number of approaches but they all run into the same issue...

let x:Double = 1234.5678
let n1:Double = x % 1.0 // n1 = 0.567800000000034
let n2:Double = x - 1234.0 // same result
let n3:Double = modf(x, &integer) // same result


Is there a way to get 0.5678 instead of 0.567800000000034 without converting to the number to a string?

Answer

Without converting it to a string, you can round up to a number of decimal places like this:

let x:Double = 1234.5678
let numberOfPlaces:Double = 4.0
let powerOfTen:Double = pow(10.0, numberOfPlaces)
let targetedDecimalPlaces:Double = round((x % 1.0) * powerOfTen) / powerOfTen

Your output would be

0.5678