ios - 使用 Swift 转换代码并出现多个错误(见图)

Question

对编码非常陌生，到目前为止只学习 Swift，在制作未更新到 IOS 9 的 IOS 应用程序的类(class)中，在尝试转换时遇到了这些错误。我已经解决了 2，但这些超出了我的范围，我无法继续前进。请帮忙。

import UIKit
import AVFoundation
class NewSoundViewController: UIViewController {

    required init?(coder aDecoder: NSCoder) {
        var baseString : String = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true)[0]

        var pathComponents = [baseString, "MyAudio.m4a"]
        var audioNSURL = NSURL.fileURLWithPathComponents(pathComponents)
        var session = AVAudioSession.sharedInstance()
        do {
            try session.setCategory(AVAudioSessionCategoryPlayAndRecord)
        } catch _ {
        }

        var recordSettings: [NSObject : AnyObject] = Dictionary()
        recordSettings[AVFormatIDKey] = kAudioFormatMPEG4AAC
        recordSettings[AVSampleRateKey] = 44100.0
        recordSettings[AVNumberOfChannelsKey] = 2

        self.audioRecorder = try AVAudioRecorder(URL: (audioNSURL)!, settings: recordSettings)
        self.audioRecorder.meteringEnabled = true
        self.audioRecorder.prepareToRecord()
    }

Error message in code

Answer 1

下面是一些可以实际编译的代码:

class NewSoundViewController: UIViewController {

    private var audioRecorder : AVAudioRecorder?

    required init?(coder aDecoder: NSCoder) {

        let session = AVAudioSession.sharedInstance()

        do {
            try session.setCategory(AVAudioSessionCategoryPlayAndRecord)
        } catch _ {
            // TODO: actually handle the error.
        }

        let baseString = NSSearchPathForDirectoriesInDomains(NSSearchPathDirectory.DocumentDirectory, NSSearchPathDomainMask.UserDomainMask, true)[0]
        let pathComponents = [baseString, "MyAudio.m4a"]
        if let audioNSURL = NSURL.fileURLWithPathComponents(pathComponents) {

            var recordSettings = [String : AnyObject]()
            recordSettings[AVFormatIDKey]         = Int(kAudioFormatMPEG4AAC)
            recordSettings[AVSampleRateKey]       = 44100.0
            recordSettings[AVNumberOfChannelsKey] = 2

            // TODO: error handling
            let audioRecorder = try? AVAudioRecorder(URL: audioNSURL, settings: recordSettings)
            self.audioRecorder = audioRecorder
            self.audioRecorder?.meteringEnabled = true
            self.audioRecorder?.prepareToRecord()
        }

        // need to call super.init
        super.init(coder: aDecoder)
    }
}

请注意，我用 let 替换了几乎所有的 var。默认情况下，您应该将所有变量设置为 let，并且仅在以后需要更改值时才使用 var。

还有一些其他风格上的变化不一定比您编写的代码更好，而是一种编写 swift 的替代方法(例如使用字典文字语法而不是显式构造函数并使用 try? 语法)。