NEW: Subscribe to Hacking with Swift+ and accelerate your learning! >>

How to specify floating-point precision in a string

Swift version: 5.2

Paul Hudson    @twostraws   

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.

Subscribe to Hacking with Swift+

Sponsor Hacking with Swift and reach the world's largest Swift community!

Available from iOS 7.0

Similar solutions…

About the Swift Knowledge Base

This is part of the Swift Knowledge Base, a free, searchable collection of solutions for common iOS questions.

BUY OUR BOOKS
Buy Pro Swift Buy Swift Design Patterns Buy Testing Swift Buy Hacking with iOS Buy Swift Coding Challenges Buy Swift on Sundays Volume One Buy Server-Side Swift (Vapor Edition) Buy Advanced iOS Volume One Buy Advanced iOS Volume Two Buy Advanced iOS Volume Three Buy Hacking with watchOS Buy Hacking with tvOS Buy Hacking with macOS Buy Dive Into SpriteKit Buy Swift in Sixty Seconds Buy Objective-C for Swift Developers Buy Server-Side Swift (Kitura Edition) Buy Beyond Code

Was this page useful? Let us know!

Average rating: 4.3/5

Link copied to your pasteboard.