快速减少（调整）Double / Float变量小数点

Question

我正在尝试减少此简单函数的小数点，该小数点将返回某事的概率，但是我了解到我需要将Double转换为String，然后减少小数并在结果视图中返回字符串值。

是否有任何方法可以使Double变量（或其他更简单的方法）在Swift 5.1中仅在结果中显示2个小数点？

    @State var pairCount = 0
    @State var rollCount = 0
    @State var pairChance : Double = 0


     Text("\(pairChance)    %")

     Button(action: {            
                      self.pairChance = Double(self.pairCount) / Double(self.rollCount) * 100.0
                      })

Answer 1

您可以使用NumberFormatter：

NumberFormatter

Answer 2

尝试在字符串插补中使用

@State var pairCount = 1.0
@State var rollCount = 3.0
@State var pairChance = "" // this should be a string, because numbers don't have a format. Strings do.

var formatter = { () -> NumberFormatter in
    let f = NumberFormatter()
    f.maximumFractionDigits = 2
    f.numberStyle = .percent
    return f
}()

var body: some View {
    VStack {
        Text("\(pairChance)")
        Button(action: {
            // here we format it
            if let formatted = self.formatter.string(from: (self.pairCount / self.rollCount) as NSNumber) {
                self.pairChance = formatted
            }
        }) {
            Text("Button")
        }
    }
}

。

specifier