Swift: use of 'self' in method call before super.init initializes self compile error

Question

我制作了一个自定义 class 来处理音频 recording/playback 并在 class 中放置了一个 Protocol。我在 UIViewController class 中实现了 Protocol 并为我的 AudioHelper class.

调用了我的 setDelegate 方法

我收到一个与我的 init() 有关的编译错误。不确定如何消除错误：

use of 'self' in method call 'setupAudioSession' before super.init initializes self

override init() {
        setupAudioSession()
        super.init()
    }

如何解决这个错误？为什么我必须重写 init()？

我的音频助手class

import Foundation
import AVFoundation

class AudioHelper: NSObject, AVAudioRecorderDelegate {

    var audioSession: AVAudioSession?
    var audioRecorder: AVAudioRecorder?
    var delegate: AudioRecorderProtocol?

    class var sharedInstance: AudioHelper {

        struct Static {
            static var instance: AudioHelper?
            static var token: dispatch_once_t = 0
        }

        dispatch_once(&Static.token) {
            Static.instance = AudioHelper()
        }

        return Static.instance!
    }

    override init() {
        setupAudioSession()
        super.init()
    }

    func setDelegate(delegate: AudioRecorderProtocol) {
        self.delegate = delegate
    }

    func setupAudioSession() {
        audioSession = AVAudioSession.sharedInstance()
        audioSession?.setCategory(AVAudioSessionCategoryPlayAndRecord, error: nil)
        audioSession?.setActive(true, error: nil)
    }

    func createAudioMessageDirectory() {
        let fm = NSFileManager.defaultManager()
        if !fm.fileExistsAtPath(GlobalVars.kAudioMessageDirectory) {
            var error: NSError?
            if !fm.createDirectoryAtPath(GlobalVars.kAudioMessageDirectory, withIntermediateDirectories: true, attributes: nil, error: &error) {
                println("Unable to create audio message directory: \(error)")
            }
        }
    }

    // MARK: Recording

    func beginRecordingAudio() {
        createAudioMessageDirectory()
        var filepath =  GlobalVars.kAudioMessageDirectory.stringByAppendingPathComponent("audiofile.aac")
        var url = NSURL(fileURLWithPath: filepath)

        var recordSettings = [
            AVFormatIDKey: kAudioFormatMPEG4AAC,
            AVSampleRateKey: 8000.0,
            AVNumberOfChannelsKey: 1,
            AVEncoderBitRateKey: 12800,
            AVLinearPCMBitDepthKey: 16,
            AVEncoderAudioQualityKey: AVAudioQuality.Max.rawValue
        ]

        println("Recorded Audio Message Saved: \(url!)")

        var error: NSError?
        audioRecorder = AVAudioRecorder(URL: url, settings: recordSettings as [NSObject : AnyObject], error: &error)

        if error == nil {
            if audioRecorder != nil {
                audioRecorder!.delegate = self
                audioRecorder!.record()
            }
        }
        else {
            println(error!.localizedDescription)
        }
    }

    func stopRecordingAudio() {
        if audioRecorder != nil {
            audioRecorder!.stop()
        }
    }

    func handleRecordAudioButtonLongPressGestureForState(state: UIGestureRecognizerState) {
        if state == UIGestureRecognizerState.Ended {
            stopRecordingAudio()
            delegate?.onRecordAudioStop()
        }
        else if state == UIGestureRecognizerState.Began {
            beginRecordingAudio()
            delegate?.onRecordAudioStop()
        }
    }

    func audioRecorderDidFinishRecording(recorder: AVAudioRecorder!, successfully flag: Bool) {
        println("Record Audio Success: \(flag)")
        delegate?.onRecordAudioFinished()
    }

    func audioRecorderEncodeErrorDidOccur(recorder: AVAudioRecorder!, error: NSError!) {
        println("Record Audio Encode Error: \(error.localizedDescription)")
    }

    // MARK: Playback

    func playAudioMessageFromUrl(messageId: String) {
        if let url = NSURL(string: GlobalVars.kUrlAudioMessage + messageId) {
            if let data = NSData(contentsOfURL: url) {
                var error: NSError? = nil
                let audioPlayer = AVAudioPlayer(data: data, error: &error)

                if error == nil {
                    if audioPlayer != nil {
                        audioPlayer.numberOfLoops = 0
                        audioPlayer.volume = 1.0
                        audioPlayer.prepareToPlay()
                        audioPlayer.play()
                    }
                }
                else {
                    println("Audio playback error: \(error?.localizedDescription)")
                }
            }
        }
    }

}

protocol AudioRecorderProtocol {
    func onRecordAudioStart()
    func onRecordAudioStop()
    func onRecordAudioFinished()
}

实现协议的我的UIViewController（去掉无关代码）

class ChatViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, AudioRecorderProtocol {

    let audioHelper = AudioHelper.sharedInstance

    let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate

    override func viewDidLoad() {
        super.viewDidLoad()

//        addDemoMessages()

        setupGestureRecognizer()
        setupKeyboardObserver()
        setupViews()
        setupTableView()
        audioHelper.setDelegate(self)
    }

    override func viewWillAppear(animated: Bool) {
        super.viewWillAppear(animated)
        getUsersFromDb()
        getMessagesFromDb()
    }

    override func viewDidAppear(animated: Bool) {
        super.viewDidAppear(animated)
        setCurrentVC()
        tableView.reloadData()

        if partnerUserId != nil && !db.doesUserExist(partnerUserId!) {
            HttpPostHelper.profileGet(userId: partnerUserId!)
        }

        requestMessagesFromServer()
    }

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        ViewHelper.scrollTableViewToBottom(tableView)
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    func handleRecordAudioButtonHold(sender: UILongPressGestureRecognizer) {
        audioHelper.handleRecordAudioButtonLongPressGestureForState(sender.state)
    }

    func onRecordAudioStart() {
        dispatch_async(dispatch_get_main_queue(), {
            ViewHelper.showToast(NSLocalizedString("RECORDING", comment: ""))
            self.recordAudioButton.imageView!.image = UIImage(named: "RecordAudioClicked")
        })
    }

    func onRecordAudioStop() {
        dispatch_async(dispatch_get_main_queue(), {
            self.recordAudioButton.imageView!.image = UIImage(named: "RecordAudio")
        })
    }

    func onRecordAudioFinished() {
        HttpPostHelper.messageAudio(partnerUserId: partnerUserId)
    }

    func playAudioFromUrl(sender: UIButton) {
        let messageId = messages[sender.tag].id
        audioHelper.playAudioMessageFromUrl(messageId)
    }

}

Answer 1

就放在super.init()下。

对象需要先由超级class初始化，然后您可以进行自定义初始化。

override init() {
    super.init()
    setupAudioSession()
}

Answer 2

如果您正在使用 MVVM 模式，并且确实需要在 super.init 之前调用某个函数，您可以随时将该函数移动到 ViewModel 并从那里调用它。只需将 viewModel 作为注入的依赖项注入即可。

Swift: use of 'self' in method call before super.init initializes self compile error

Swift: use of 'self' in method call before super.init initializes self compile error

delegates

protocols

ios