Question

在Swift 2.0中，如果我执行以下操作：

panel.beginSheetModalForWindow(self.view.window!) { (result) in

  switch result {
  // Save was selected
  case NSFileHandlingPanelOKButton:
    self.writeFile(fileString, fileURL: panel.URL!)
    // something else was selected
  default:
    break
  }
}

使用以下功能，它可以编译和工作。

  func writeFile(fileString: String, fileURL: NSURL) {
    do {
      try fileString.writeToURL(fileURL, atomically: true, encoding: NSUTF8StringEncoding)
    } catch let error as NSError {
      fatalError("Error writing to file - \(error)")
    }
  }

但是，如果我将这两者结合起来：

panel.beginSheetModalForWindow(self.view.window!) { (result) in
  switch result {
  // Save was selected
  case NSFileHandlingPanelOKButton:
    do {
      try fileString.writeToURL(fileURL, atomically: true, encoding: NSUTF8StringEncoding)
    } catch let error as NSError {
      fatalError("Error writing to file - \(error)")
    }
    // something else was selected
  default:
    break
  }
}

它不会编译。我收到编译错误：

投掷类型＆＃39;（）投掷功能的转换无效 - ＆gt; ＆＃39;到非投掷函数类型＆＃39;（Int） - ＆gt;空隙＆＃39;

为什么？

Answer 1

添加默认的catch块，如下所示：

[SentiSynset('decelerate.v.01'), SentiSynset('slow.v.02'), \
SentiSynset('slow.v.03'), SentiSynset('slow.a.01'),SentiSynset('slow.a.02'), \
SentiSynset('slow.a.04'), SentiSynset('slowly.r.01'),SentiSynset('behind.r.03')]

http://www.hackingwithswift.com/new-syntax-swift-2-error-handling-try-catch

Answer 2

我发现了答案（在新的Apple开发者论坛上）。

如果你这样做，它可以工作：

panel.beginSheetModalForWindow(self.view.window!) { (result) in
  switch result {
  case NSFileHandlingPanelOKButton:
    // Save was selected
    do {
      try fileString.writeToURL(panel.URL!, atomically: true, encoding: NSUTF8StringEncoding)
    } catch let error as NSError {
      fatalError("Error writing to file : \(error)")
    } catch {
      fatalError("Error")
    }
  default:
    // something else was selected
    break
  }
}

问题是“捕获”并非详尽无遗，导致投掷传播到封闭函数（不会“抛出”）。

尝试在beginSheetModalForWindow

2 个答案: