Swift version: 5.1
Swift's string interpolation makes it easy to put floating-point numbers into a string, but it lacks the ability to specify precision. For example, if a number is 45.6789, you might only want to show two digits after the decimal place.
Here's an example using basic string interpolation:
let angle = 45.6789 let raw = "Angle: \(angle)"
That will make the
raw value equal to "Angle: 45.6789". But if you wanted to round the angle to two decimal places, you would use this code instead:
let formatted = String(format: "Angle: %.2f", angle)
The "%f" format string means "a floating point number," but "%.2f" means "a floating-point number with two digits after the decimal point. When you use this initializer, Swift will automatically round the final digit as needed based on the following number.
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Available from iOS 7.0
This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.