在 beginSheetModalForWindow 中尝试

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
  }
}

使用如下函数，编译运行。

  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，如果我像这样结合两者：

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。我收到一个编译器错误：

从“() throws ->”类型的抛出函数到非抛出函数类型“(Int) -> Void”的无效转换

为什么？

Answer 1

像这样添加默认的 catch 块：

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

}

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

Answer 2

我找到了答案（在新的 Apple Developer 论坛上）。

如果你这样做它会起作用：

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 "catch" 并不详尽，这导致抛出被传播到封闭函数（而不是 "throw"）。

在 beginSheetModalForWindow 中尝试

do try in beginSheetModalForWindow

error-handling

swift

swift2