ios - 计算多个音频文件顺序播放的总时长/Swift 3、4

Question

例如，有40个音频文件(A1，A2，...，A40)，通过AVAudioPlayer调出不同编号的文件，依次播放。例如，前 5 个(A1、A2、...、A5)。

var speechPlayer = AVAudioPlayer ()
var currentPlayingItems: [String] = []

fileprivate func prepareAudioItemsToPlay () {
var result: [String] = []

    if (introSwitch.isOn) {    
    result.append ( "Intro")
    }

result += audioFileNamesForCurrentLessonType

currentPlayingItems = result.flatMap ({Bundle.main.path (forResource: $ 0, ofType: "m4a")})
currentPlayingItemNumber = 0

fileprivate var audioFileNamesForCurrentLessonType: [String] {
    guard let type = selectedLessonType else {return []}
    switch type {

    case .lesson1:
    if (statusSelection.selectedSegmentIndex == 0) {
    return ["A1", "A2", "A3", "A4", "A5"]
    }
    else if (statusSelection.selectedSegmentIndex == 1) {
    return ["A1", "A6", "A3, "A7", "A8", "A9","A10"] 
    }
...
}

如何获得在所选类(class)/状态中播放的所有音频文件的总运行时间？例如:Lesson1, first (exercise) Status:
简介，A1、A2、A3、A4、A5(135 秒，下文)

让我们简单地假设音频文件的持续时间(以秒为单位)如下:
A1 = 1, A2 = 2, A3 = 3, ..., A40 = 40, Intro = 120 这些在列表(数组、元组、字典？)中给出。

我需要数组、元组还是字典以及如何从这个列表中获取值(秒)(Array, Tuple,...)对于 Lesson(i)/status(j) 将它们加在一起，计算持续时间并显示出来？

Answer 1

let durations:[String:Int] = ["A1": 1, "A2": 2, "A3": 3, "Intro": 120]
let fileNames:[String] = ["A1", "A3"]
let totalDuration = durations.filter{ fileNames.contains($0.key) }.values.reduce(0, +)

对于非唯一值:

let totalDuration = fileNames.compactMap{ durations[$0] }.reduce(0, +)

使用 AVURLAsset 获取每个音频文件的持续时间。