CODEWITHSUNDEEP
swiftxcode6rounding
rocket101
rocket101

Reputation: 7537

Rounding in Swift with round()

While playing around, I found the round() function in swift. It can be used as below:

round(0.8)

Which will return 1, as expected. Here's my question:

how do I round by thousandths in swift?

I want to be able to plug in a number, say 0.6849, and get 0.685 back. How does round() do this? Or, does it not, in which case, what function does?

Upvotes: 53

Views: 91102

Answers (8)

user15057879
user15057879

Reputation: 21

var a=1.2344 
var b:String = String(format: "%0.2f",a) 
print(b)

Output:

1.23

The output you got is of string type. So, you need to convert into other types if needed. The below link tells you how to convert:

https://supereasyapps.com/blog/2015/9/28/how-to-convert-strings-into-double-and-float-values-using-swift-2#:~:text=Convert%20Swift%20String%20to%20Double,(Double(%22200.0%22)!)

Upvotes: 2

Mehrshad Khansarian
Mehrshad Khansarian

Reputation: 129

Take a look at Apple's documentation for round() and rounded(_:).

Upvotes: 1

Suragch
Suragch

Reputation: 512776

Updated answer

The round(someDecimal) is the old C style. As of Swift 3, doubles and floats have a built in Swift function.

var x = 0.8
x.round() // x is 1.0 (rounds x in place)

or

var x = 0.8
var y = x.rounded() // y is 1.0, x is 0.8

See my answer fuller answer here (or here) for more details about how different rounding rules can be used.

As other answers have noted, if you want to round to the thousandth, then multiply temporarily by 1000 before you round.

Upvotes: 21

Halyna Rubashko
Halyna Rubashko

Reputation: 605

Swift 4:

(x/1000).rounded()*1000

Upvotes: 4

matrinox
matrinox

Reputation: 472

func round(value: Float, decimalPlaces: UInt) {
  decimalValue = pow(10, decimalPlaces)
  round(value * decimalValue) / decimalValue
}
…
func round(value: CGFloat, decimalPlaces: UInt)
func round(value: Double, decimalPlaces: UInt)
func roundf(value: Float, decimalPlaces: UInt)

Upvotes: 11

Sethmr
Sethmr

Reputation: 3084

This will round to any value not limited by powers of 10.

extension Double {
    func roundToNearestValue(value: Double) -> Double {
        let remainder = self % value
        let shouldRoundUp = remainder >= value/2 ? true : false
        let multiple = floor(self / value)
        let returnValue = !shouldRoundUp ? value * multiple : value * multiple + value
        return returnValue
    }
}

Upvotes: 3

Dan Rosenstark
Dan Rosenstark

Reputation: 69787

Here's one way to do it. You could easily do this for Float, or probably make it generic so it's for any of those.

public extension CGFloat {
    func roundToDecimals(decimals: Int = 2) -> CGFloat {
        let multiplier = CGFloat(10^decimals)
        return round(multiplier * self) / multiplier
    }
}

Upvotes: 4

Clement Bisaillon
Clement Bisaillon

Reputation: 5187

You can do:

round(1000 * x) / 1000

Upvotes: 96

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