如何在swift中循环？[副本]

Question

我想把这个代码的答案四舍五入到小数点后两位。我尝试了很多方法，但没有一种对我有效。请帮忙！

import Foundation

var yen: Double = 10
var krona: Double = 10
var rupee: Double = 10
var totalMoney: Double

var yenRate = 0.0088
var kronaRate = 0.116
var rupeeRate = 0.013


totalMoney = yenRate*yen + kronaRate*krona + rupeeRate*rupeeRate

print("The total of all currencies is equal to \(totalMoney) in USD.")

Answer 1

有很多方法可以做到这一点

>

如果您希望值以字符串格式将其分配给标签

 var yen: Double = 10
 var krona: Double = 10
 var rupee: Double = 10
 var totalMoney: Double
 var yenRate = 0.0088
 var kronaRate = 0.116
 var rupeeRate = 0.013


 totalMoney = yenRate*yen + kronaRate*krona + rupeeRate*rupeeRate

 let doubleStr = String(format: "%.2f", totalMoney)

 print(doubleStr)

此处%.2f将其四舍五入到2个小数点，这是一个字符串值

2.you在您的项目中添加此扩展

extension Double {
func round(to places: Int) -> Double {
    let divisor = pow(10.0, Double(places))
    return (self * divisor).rounded() / divisor
  }
}

然后在你的课堂上使用它，比如

totalMoney = yenRate*yen + kronaRate*krona + rupeeRate*rupeeRate
let totlaMoneyInDouble = Double(totlaMoney) 

这将返回一个双倍值