在swift中声明变量时可以使用通配符吗？
在swift中声明变量时可以使用通配符吗？
提问于 2018-06-09 21:46:42
我正在通过构建一个Soundboard应用程序来学习编码。我正在使用audioEngine播放一些声音，在我改变了一些曲调之后。在我的viewDidLoad中，我声明我的variables
var audioFile1 = AVAudioFile()
var audioFile2 = AVAudioFile()
if let filePath = Bundle.main.path(forResource: "PeteNope", ofType:
"mp3") {
let filePathURL = URL(fileURLWithPath: filePath)
setPlayerFile(filePathURL)
}
if let filePath2 = Bundle.main.path(forResource: "Law_WOW", ofType:
"mp3") {
let filePath2URL = URL(fileURLWithPath: filePath2)
setPlayerFile2(filePath2URL)
}
func setPlayerFile(_ fileURL: URL) {
do {
let file1 = try AVAudioFile(forReading: fileURL)
self.audioFile1 = file1
} catch {
fatalError("Could not create AVAudioFile instance. error: \(error).")
}
}
func setPlayerFile2(_ fileURL: URL) {
do {
let file2 = try AVAudioFile(forReading: fileURL)
self.audioFile2 = file2
} catch {
fatalError("Could not create AVAudioFile instance. error: \(error).")
}
}然后，我按如下方式连接nodes：
audioEngine.attach(pitchPlayer)
audioEngine.attach(timePitch)
audioEngine.connect(pitchPlayer, to: timePitch, format: audioFile1.processingFormat)
audioEngine.connect(timePitch, to: audioEngine.outputNode, format: audioFile1.processingFormat)
audioEngine.connect(pitchPlayer, to: timePitch, format: audioFile2.processingFormat)
audioEngine.connect(timePitch, to: audioEngine.outputNode, format: audioFile2.processingFormat) 所以，我的问题是，由于变量除了一个数字之外都是相同的，有没有一种方法可以通过编程来编写它，这样我就不必单独声明nodes了。
回答 1
Stack Overflow用户
回答已采纳
发布于 2018-06-10 00:56:57
根据我对您问题的理解，您有许多"PeterNope“和"Law_WOW”类型的资源，并且希望快速地将它们添加为节点。
您可以按如下方式重构代码，以添加任意数量的资源：
var resources = ["PeterNope", "Law_WOW", "otherResource1", "otherResource2", ...]
func setPlayerFile(_ fileName: String) {
// make sure resource exists and break if not.
guard let filePath = Bundle.main.path(forResource: fileName, ofType: "mp3") else {
print ("resource file \(fileName) does not exist")
return
}
let fileURL = URL(fileURLWithPath: filePath)
// open file from resource
do {
let file = try AVAudioFile(forReading: fileURL)
} catch {
fatalError("Could not create AVAudioFile instance. error: \(error).")
}
// connect nodes
connect(pitchPlayer, to: timePitch, format: file.processingFormat)
audioEngine.connect(timePitch, to: audioEngine.outputNode, format: file.processingFormat)
}
// connect all resources
attach(pitchPlayer)
audioEngine.attach(timePitch)
for index in 0..(resources.count - 1) {
setPlayer(resources[index]
}
// or quicker and swiftier:
resources.forEach { setPlayerFile($0) }我推荐阅读for循环和控制流的一般内容：https://docs.swift.org/swift-book/LanguageGuide/ControlFlow.html
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原文链接：
https://stackoverflow.com/questions/50774934
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