Floating point precision in Swift String

If you’d like to interpolate a float or a double with a String in Swift, use the %f String format specifier with appropriate number in order to specify floating point precision.

Given a Float or a Double value:

var value = 4.53978

Create a string with value rounded to one decimal place which results in 4.5:

let stringValue = String(format: "Value: %.1f", value)

String with value rounded to two decimal places results in 4.54:

let stringValue = String(format: "Value: %.2f", value)

String with value rounded to three decimal places results in 4.540:

let stringValue = String(format: "Value: %.3f", value)

Note that Swift automatically rounds the value for you.

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