Dates, Formatting, and Text

Formatted Numbers

Formatting can turn a numeric value into text with a chosen precision.

Choose decimal places

price
formatted_numbers.swift
Replay: real traced execution (multi-file project)
import Foundation

let price = 12.345
let formatted = String(format: "%.2f", price)
let message = "price=\(formatted)"

print(message)

import Foundation

let price = 9.876
let formatted = String(format: "%.2f", price)
let message = "price=\(formatted)"

print(message)

import Foundation

let price = 20.0
let formatted = String(format: "%.2f", price)
let message = "price=\(formatted)"

print(message)

  1. price ← 12.345, formatted ← 12.35, message ← price=12.35

    3let price→ 12.345 = 12.345  //@price=9.876, 20.04let formatted→ 12.35 = String(format: "%.2f", price12.345)5let message→ price=12.35 = "price=\(formatted12.35)"67print(messageprice=12.35)
    outputprice=12.35

  1. price ← 9.876, formatted ← 9.88, message ← price=9.88

    3let price→ 9.876 = 9.8764let formatted→ 9.88 = String(format: "%.2f", price9.876)5let message→ price=9.88 = "price=\(formatted9.88)"67print(messageprice=9.88)
    outputprice=9.88

  1. price ← 20.0, formatted ← 20.00, message ← price=20.00

    3let price→ 20.0 = 20.04let formatted→ 20.00 = String(format: "%.2f", price20.0)5let message→ price=20.00 = "price=\(formatted20.00)"67print(messageprice=20.00)
    outputprice=20.00
number formatting `String(format:)` produces a string representation with a predictable number of decimal places.