Cocoa 如何将AVAudioRecorder声明为全局变量

我很难理解为什么我不能声明这里看到的记录器变量，因为它可用于类中的任何操作

编辑以完整显示仍显示相同行为的新测试项目。 我似乎无法在全球范围内声明记录器变量。见评论：

import Cocoa
import AVFoundation

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate, AVAudioRecorderDelegate {

    var recorder : AVAudioRecorder = AVAudioRecorder() // remove this and clean up un-declared recorder vars, and it appears to record as expected

    @IBOutlet weak var window: NSWindow!


    func applicationDidFinishLaunching(aNotification: NSNotification) {
        // Insert code here to initialize your application
    }

    func applicationWillTerminate(aNotification: NSNotification) {
        // Insert code here to tear down your application
    }


    @IBAction func startRecording(sender: AnyObject) {
        var recordSettings = [
            AVFormatIDKey: kAudioFormatAppleLossless,
            AVEncoderAudioQualityKey : AVAudioQuality.Medium.rawValue,
            AVEncoderBitRateKey : 16,
            AVNumberOfChannelsKey: 2,
            AVSampleRateKey : 44100.0
        ]

        var theRecordingUrl = "/Users/myMbp/Desktop/test.wav" // !!! #### ammend the url for testing #### !!!
        var theRecordingUrlAsUrl = NSURL(string: theRecordingUrl)!
        println(theRecordingUrlAsUrl) // still looks good before crash

        var recorderError: NSError?
        recorder = AVAudioRecorder(URL: theRecordingUrlAsUrl, settings: recordSettings, error: &recorderError) // with the global recorder var it crashes here
        if let e = recorderError {
            println(e.localizedDescription)
        } else {
            recorder.delegate = self
            recorder.meteringEnabled = true
            if recorder.prepareToRecord() {
                println("recording prepared")
            }else{
                println("fialed to prepare recordeing")
            }
            if recorder.record() {
                println("started recording")
            }else{
                println("fialed to start recordeing")
            }
        }

    }


    @IBAction func stopRecording(sender: AnyObject) {
        recorder.stop()
    }



}

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大量的实验发现，答案是，我必须声明全局记录器变量，如下所示：

var recorder:AVAudioRecorder!