可选类型“String？”的值不解包;你的意思是使用'！要么 '？'？ [英] Value of optional type 'String?' not unwrapped; did you mean to use '!' or '?'?

问题描述

我在Swift中定义一个类：

  class RecordedAudio：NSObject {
 var title：String！ 
 var filePathUrl：NSURL！ 
 
 init（title：String，filePathUrl：NSURL）{
 self.title = title 
 self.filePathUrl = filePathUrl 
} 
} 
 
 
 
 
之后，我在控制器中声明这个全局变量。
  var recordedAudio：RecordedAudio！ 
  
然后，在此函数中创建实例：
  func audioRecorderDidFinishRecording（record：AVAudioRecorder !, successfully flag：Bool）{
 if（flag）{
 //保存录制的音频
 recordedAudio = RecordedAudio（title：recorder.url.lastPathComponent，filePathUrl：recorder.url）
 ... 
  
但我在行中创建了RecordedAudio的实例的错误消息：
 
 
可选类型String？ ;你是说使用'！'还是'？'？
 
 
你能帮我一下吗？我是Swift的初学者... 
解决方案
  lastPathComponent 可选字符串：
 
 
 
  
 
 
 
但您的 RecordedAudio 似乎需要 String 不是 String？。 
有两个简单的方法来修复它：
 
 
 
添加！，如果你确定lastPathComponent从不返回nil 
  recordedAudio = RecordedAudio（title：recorder.url.lastPathComponent !, filePathUrl：recorder.url）
  
或
 
 
 
如果lastPathComponent为nil，请使用默认标题
  recordedAudio = RecordedAudio（title：recorder.url.lastPathComponent ??Default title，filePathUrl：recorder.url）
  
 
I define a class in Swift like that:
class RecordedAudio: NSObject {
    var title: String!
    var filePathUrl: NSURL!

    init(title: String, filePathUrl: NSURL) {
        self.title = title
        self.filePathUrl = filePathUrl
    }
}
After that, I declare the global var of this one in controller
var recordedAudio: RecordedAudio!
And then, create the instance in this function:
func audioRecorderDidFinishRecording(recorder: AVAudioRecorder!, successfully flag: Bool) {
        if(flag){
            // save recorded audio
           recordedAudio = RecordedAudio(title: recorder.url.lastPathComponent, filePathUrl: recorder.url)
...
But I got the error message in line I create the instance of RecordedAudio: 

  
Value of optional type 'String?' not unwrapped; did you mean to use '!' or '?'?
Could you help me this case? I am a beginner of Swift...
解决方案
lastPathComponent returns an optional String:



but your RecordedAudio seems to require String not String?.
There are two easy ways to fix it:

Add ! in case you are sure lastPathComponent will never return nil
recordedAudio = RecordedAudio(title: recorder.url.lastPathComponent!, filePathUrl: recorder.url)
or

Use a default title in case lastPathComponent is nil
recordedAudio = RecordedAudio(title: recorder.url.lastPathComponent ?? "Default title", filePathUrl: recorder.url)


                        
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