尝试在 Swift 中组合数字和变量

Question

我是一个新手，正在努力通过将数字和变量组合在一起来创建 0.2。但我想我以某种方式完全倒退了。有人可以帮忙吗？

//将'20%'的字符串变成'2'。

let tipPercent = tip.prefix(1)

//将字符串转换为'2'的Int

let tipPercent1: Int = Int(tipPercent) ?? 0

//所以现在我想将 0. 与变量 tipPercent1 结合起来。这将创建“0.2”

let twentyTipamount = (billamount * 0.tipPercent1) + billamount

Answer 1

您似乎只想将百分比字符串解析为数字。你应该使用 NumberFormatter.

let numberFormatter = NumberFormatter()
numberFormatter.locale = Locale(identifier: "en-US_POSIX")
// or whatever other locale that your tip is written in

numberFormatter.numberStyle = .percent
// if the tip cannot be parsed, use 0 as the default
let tipRate = numberFormatter.number(from: tip)?.doubleValue ?? 0
// or you can do something else:
// guard let tipRate = numberFormatter.number(from: tip)?.doubleValue else { ... }

// calculate the amount after tips
let totalAmount = billamount * (1 + tipRate)

尝试在 Swift 中组合数字和变量

Trying to combine a number and variable in Swift

var

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