Convert Float to Int in Swift

Question

You can convert Float to Int in Swift like this:

var myIntValue:Int = Int(myFloatValue)
println "My value is \(myIntValue)"

You can also achieve this result with @paulm's comment:

var myIntValue = Int(myFloatValue)

Explicit Conversion

Converting to Int will lose any precision (effectively rounding down). By accessing the math libraries you can perform explicit conversions. For example:

If you wanted to round down and convert to integer:

let f = 10.51
let y = Int(floor(f))

result is 10.

If you wanted to round up and convert to integer:

let f = 10.51
let y = Int(ceil(f))

result is 11.

If you want to explicitly round to the nearest integer

let f = 10.51
let y = Int(round(f))

result is 11.

In the latter case, this might seem pedantic, but it's semantically clearer as there is no implicit conversion...important if you're doing signal processing for example.

There are lots of ways to round number with precision. You should eventually use swift's standard library method rounded() to round float number with desired precision.

To round up use .up rule:

let f: Float = 2.2
let i = Int(f.rounded(.up)) // 3

To round down use .down rule:

let f: Float = 2.2
let i = Int(f.rounded(.down)) // 2

To round to the nearest integer use .toNearestOrEven rule:

let f: Float = 2.2
let i = Int(f.rounded(.toNearestOrEven)) // 2

Be aware of the following example:

let f: Float = 2.5
let i = Int(roundf(f)) // 3
let j = Int(f.rounded(.toNearestOrEven)) // 2

Converting is simple:

let float = Float(1.1) // 1.1
let int = Int(float) // 1

But it is not safe:

let float = Float(Int.max) + 1
let int = Int(float)

Will due to a nice crash:

fatal error: floating point value can not be converted to Int because it is greater than Int.max

So I've created an extension that handles overflow:

extension Double {
    // If you don't want your code crash on each overflow, use this function that operates on optionals
    // E.g.: Int(Double(Int.max) + 1) will crash:
    // fatal error: floating point value can not be converted to Int because it is greater than Int.max
    func toInt() -> Int? {
        if self > Double(Int.min) && self < Double(Int.max) {
            return Int(self)
        } else {
            return nil
        }
    }
}


extension Float {
    func toInt() -> Int? {
        if self > Float(Int.min) && self < Float(Int.max) {
            return Int(self)
        } else {
            return nil
        }
    }
}

I hope this can help someone

You can get an integer representation of your float by passing the float into the Integer initializer method.

Example:

Int(myFloat)

Keep in mind, that any numbers after the decimal point will be loss. Meaning, 3.9 is an Int of 3 and 8.99999 is an integer of 8.

Like this:

var float:Float = 2.2 // 2.2
var integer:Int = Int(float) // 2 .. will always round down.  3.9 will be 3
var anotherFloat: Float = Float(integer) // 2.0

Use a function style conversion (found in section labeled "Integer and Floating-Point Conversion" from "The Swift Programming Language."[iTunes link])

  1> Int(3.4)
$R1: Int = 3