快速将Base64字符串转换为音频文件

Question

我从XML解析中收到了一个base64字符串（字符串太长），我想将其转换为音频文件，然后将那个base64字符串转换为NSData并成功写入文档目录中，但是当我返回时该音频文件没有播放。有人面对吗？

 func getPackages() {
        let semaphore = DispatchSemaphore (value: 0)
        let parameters = "<soap12:Envelope xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\" xmlns:soap12=\"http://www.w3.org/2003/05/soap-envelope\">\n  <soap12:Body>\n    <GetPackage xmlns=\"http://tempuri.org/\">\n      <data>\n        <UID>123</UID>\n        <Platform>iOS</Platform>\n        <PackageCode>UA</PackageCode>\n      </data>\n    </GetPackage>\n  </soap12:Body>\n</soap12:Envelope>"
        let postData = parameters.data(using: .utf8)
        var request = URLRequest(url: URL(string: "https://www.cool-english.info/Service.asmx?wsdl")!,timeoutInterval: Double.infinity)
        request.addValue("application/soap+xml; charset=utf-8", forHTTPHeaderField: "Content-Type")
        
        request.httpMethod = "POST"
        request.httpBody = postData
        let task = URLSession.shared.dataTask(with: request) { data, response, error in
            guard let data = data else {
                print(String(describing: error))
                return
            }
            let parser = XMLParser(data: data)
            parser.delegate = self
            parser.parse()
            semaphore.signal()
        }
        task.resume()
        semaphore.wait()
    }

// XML解析委托

    func parser(_ parser: XMLParser, foundCharacters string: String) {
        let data = string.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines)
        if (!data.isEmpty) {
            if currentParsingElement == "GetPackageResult" {
                packageResult += data
                self.saveBase64StringToAudio(packageResult)
            }
        }
    }
    

//用于在文档目录中写入

func saveBase64StringToAudio(_ base64String: String) {

        guard
            var documentsURL = (FileManager.default.urls(for: .documentDirectory, in: .userDomainMask)).last,
            let convertedData = Data(base64Encoded: base64String)
            else {
            //handle error when getting documents URL
            return
        }

        //name your file however you prefer0
        documentsURL.appendPathComponent("audio.mp3")
        do {
            try convertedData.write(to: documentsURL)            
            do {
                audioPlayer = try AVAudioPlayer(contentsOf: documentsURL)
                guard let player = audioPlayer else { return }
                player.play()
            } catch let error {
                print(error.localizedDescription)
            }
        } catch {
            //handle write error here
        }
        print(documentsURL)
    }