swift - 如何在 Swift 中获取范围的值

Question

我用 swift 编写了以下函数:

func FFT_Analyzer (frequencies:[Double], magnitudes:[Double], sort_mag:[Double], harmonics:[Double]) -> (chatter_freq:Double,
    chatter_mag:Double) {


    //establish a counter to iterate through all the arrays: 
    var ffcounter = 0
    var temp_Bool = 0
    var chatter_freq:Double = 0
    var chatter_mag:Double = 0

    //establish a while loop that runs for the entirety of the frequency/FFT arrays:
    while  ffcounter < frequencies.count {

        //use y_descend, to go down the frequencies with descending magnitude
        var chatter_mag:Double = sort_mag[ffcounter]
        println("The chatter magnitude is: \(chatter_mag)")

        //determine the index of the frequency with highest amplitude
        var mag_index = find(magnitudes, chatter_mag)
        println("The chatter inded is: \(mag_index)")

        //using the index, find the corresponding frequency:
        var chatter_freq:Double = frequencies[mag_index!]
        println("The chatter frequency is: \(chatter_freq)")

        //use a FOR loop to check whether this frequency is a forced frequency/harmonic:
        for element in harmonics {
            if (((element-1) < chatter_freq) && (chatter_freq < (element+1))) {
                temp_Bool = 0
                break
            }

            else{
                temp_Bool = 1
                continue
            }
        }
        if temp_Bool == 0 {
            ffcounter = ffcounter + 1
            continue
        }
        else {
            println(chatter_freq)
            println(chatter_mag)
            break
        }

        //return (chatter_freq, chatter_mag)
    }
    println(ffcounter)
    println(temp_Bool)
    println(chatter_freq)
    println(chatter_mag)

    return (chatter_freq, chatter_mag)
}

为了使变量在作用域内，我在 while 和 for 循环之前定义了 ffcounter、temp_Bool、chatter_freq 和 chatter_mag。但是我遇到了以下问题:

当我的代码运行完成时，ffcounter 和 temp_Bool 将更新为其最终值(分别为 2 和 1)，但是，chatter_freq 和 chatter_mag 的值不会传递到函数末尾。换句话说，chatter_freq 和 chatter_mag 是 while 循环内的更新，但我无法将这些值传递到 while 循环之外。结果chatter_freq 和chatter_mag 等于它们的初始值:0.0。

有谁知道如何将值移出更新代码块的“范围”？

Answer 1

您正在循环内声明这两个变量的新实例，即使您之前已在循环外声明了它们。

只需将循环内的内容更改为:

var chatter_mag:Double = sort_mag[ffcounter]
var chatter_freq:Double = frequencies[mag_index!]

至:

chatter_mag = sort_mag[ffcounter]
chatter_freq = frequencies[mag_index!]