Getting the decimal part of a double in Swift

Question

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:         


        

Answer 1

It's impossible to create a solution that will work for all Doubles. And if the other answers ever worked, which I also believe is impossible, they don't anymore.

let _5678 = 1234.5678.description.drop { $0 != "." } .description // ".5678"
Double(_5678)  // 0.5678

let _567 = 1234.567.description.drop { $0 != "." } .description // ".567"
Double(_567) // 0.5669999999999999

Answer 2

Same approach as Alessandro Ornano implemented as an instance property of FloatingPoint protocol:

Xcode 11 • Swift 5.1

import Foundation

extension FloatingPoint {
    var whole: Self { modf(self).0 }
    var fraction: Self { modf(self).1 }
}

---

1.2.whole    // 1
1.2.fraction // 0.2

---

If you need the fraction digits and preserve its precision digits you would need to use Swift Decimal type and initialize it with a String:

extension Decimal {
    func rounded(_ roundingMode: NSDecimalNumber.RoundingMode = .bankers) -> Decimal {
        var result = Decimal()
        var number = self
        NSDecimalRound(&result, &number, 0, roundingMode)
        return result
    }
    var whole: Decimal { self < 0 ? rounded(.up) : rounded(.down) }
    var fraction: Decimal { self - whole }
}

---

let decimal = Decimal(string: "1234.99999999")!  // 1234.99999999
let fractional = decimal.fraction                // 0.99999999
let whole = decimal.whole                        // 1234
let sum = whole + fractional                     // 1234.99999999

Answer 3

There’s a function in C’s math library, and many programming languages, Swift included, give you access to it. It’s called modf, and in Swift, it works like this

// modf returns a 2-element tuple,

// with the whole number part in the first element,

// and the fraction part in the second element

let splitPi = modf(3.141592)

splitPi.0 // 3.0

splitPi.1 // 0.141592

You can create an extension like below,

extension Double {

    func getWholeNumber() -> Double {

        return modf(self).0

    }

    func getFractionNumber() -> Double {

        return modf(self).1

    }

}

Answer 4

You can use truncatingRemainder and 1 as the divider.

Returns the remainder of this value divided by the given value using truncating division.

Apple doc

Example:

let myDouble1: Double = 12.25
let myDouble2: Double = 12.5
let myDouble3: Double = 12.75

let remainder1 = myDouble1.truncatingRemainder(dividingBy: 1)
let remainder2 = myDouble2.truncatingRemainder(dividingBy: 1)
let remainder3 = myDouble3.truncatingRemainder(dividingBy: 1)

remainder1 -> 0.25
remainder2 -> 0.5
remainder3 -> 0.75

Answer 5

Use Float since it has less precision digits than Double

let x:Double = 1234.5678
let n1:Float = Float(x % 1)           // n1 = 0.5678

Answer 6

Swift 5.1

let x:Double = 1234.5678

let decimalPart:Double = x.truncatingRemainder(dividingBy: 1)    //0.5678
let integerPart:Double = x.rounded(.towardZero)                   //1234

Both of these methods return Double value.

if you want an integer number as integer part, you can just use

Int(x)