打开可选值时意外发现nil（AppleScript结果）

2 回答

• 1

  实际上错误可能来自 NSAppleScript(source: script)! 所以正确的解决方案是返回一个Optional String而不是使用force unwrapping：

  func runAppleScript(script:String) -> String? {
      let errorInfo: AutoreleasingUnsafeMutablePointer<NSDictionary?> = nil
      let startAtLoginScript = NSAppleScript(source: script)
      let theDescriptor = startAtLoginScript?.executeAndReturnError(errorInfo)
      return theDescriptor?.stringValue
  }
  
  if let scriptResult = runAppleScript("tell app \"Spotify\" to playpause") {
      NSLog("\(scriptResult)")
  } else {
      print("the script execution failed")
  }
  

  如果您在失败时更喜欢使用默认值而不是nil，则无需返回Optional：

  func runAppleScript(script:String) -> String {
      let errorInfo: AutoreleasingUnsafeMutablePointer<NSDictionary?> = nil
      let startAtLoginScript = NSAppleScript(source: script)
      let theDescriptor = startAtLoginScript?.executeAndReturnError(errorInfo)
      return theDescriptor?.stringValue ?? ""  // if nil, returns the default ""
  }
  
  let scriptResult = runAppleScript("tell app \"Spotify\" to playpause")
  NSLog("\(scriptResult)")
  

  至于使用新的 Swift 2 错误处理系统，你在 runAppleScript 中使用的所有方法都没有抛出错误，因此只有在你使用自定义错误类型并自己抛出错误时它才会起作用 . 例：

  enum MyAppleScriptError: ErrorType {
      case ExecutingScriptFailed
      case GettingStringValueFailed
  }
  
  func runAppleScript(script:String) throws -> String {
      let errorInfo: AutoreleasingUnsafeMutablePointer<NSDictionary?> = nil
      let startAtLoginScript = NSAppleScript(source: script)
      guard let theDescriptor = startAtLoginScript?.executeAndReturnError(errorInfo) else {
          throw MyAppleScriptError.ExecutingScriptFailed
      }
      guard let value = theDescriptor.stringValue else {
          throw MyAppleScriptError.GettingStringValueFailed
      }
      return value
  }
  
  do {
      let scriptResult = try runAppleScript("tell app \"Spotify\" to playpause")
      NSLog("\(scriptResult)")
  } catch {
      print(error)
  }
  

  Swift 3

  同样的想法，但一些实现细节是不同的 .

  func runAppleScript(_ script:String) -> String? {
      let errorInfo: AutoreleasingUnsafeMutablePointer<NSDictionary?>? = nil
      if let startAtLoginScript = NSAppleScript(source: script) {
          let theDescriptor = startAtLoginScript.executeAndReturnError(errorInfo)
          return theDescriptor.stringValue
      }
      return nil
  }
  
  if let scriptResult = runAppleScript("tell app \"Spotify\" to playpause") {
      NSLog("\(scriptResult)")
  } else {
      print("no return value")
  }
  

  并且有错误处理：

  enum MyAppleScriptError: ErrorProtocol {
      case ExecutingScriptFailed
      case GettingStringValueFailed
  }
  
  func runAppleScript(_ script:String) throws -> String {
      let errorInfo: AutoreleasingUnsafeMutablePointer<NSDictionary?>? = nil
      let startAtLoginScript = NSAppleScript(source: script)
      guard let theDescriptor = startAtLoginScript?.executeAndReturnError(errorInfo) else {
          throw MyAppleScriptError.ExecutingScriptFailed
      }
      guard let value = theDescriptor.stringValue else {
          throw MyAppleScriptError.GettingStringValueFailed
      }
      return value
  }
  
  do {
      let scriptResult = try runAppleScript("tell app \"Spotify\" to playpause")
      NSLog("\(scriptResult)")
  } catch {
      print(error)
  }
  

  回复于 2024-05-04T07:55:45+08:00
• 0

  我修复了自己的代码 .

  import Foundation
  
  func runAppleScript(script:String) -> String
  {
      let theResult:String
      let errorInfo = AutoreleasingUnsafeMutablePointer<NSDictionary?>()
      let startAtLoginScript: NSAppleScript = NSAppleScript(source: script)!
      let theDiscriptor:NSAppleEventDescriptor = startAtLoginScript.executeAndReturnError(errorInfo)
      if let _ = theDiscriptor.stringValue
      {
          theResult = theDiscriptor.stringValue!
      } else {
          theResult = ""
      }
  
      return theResult
  }
  
  
  
  let scriptResult = runAppleScript("")
  

  我要做的是在解开之前检查theDiscriptor.stringValue是否有值 . 我得到的错误是因为我在打开包装后试图检查该值 . 只需删除支票上的 ! 即可修复我的问题 .

  Edit

  在Swift 3中尝试此操作时，代码 let errorInfo = AutoreleasingUnsafeMutablePointer<NSDictionary?>() 不再有效 . 为了解决这个问题，我更新了代码 .

  func runAppleScript(script:String) -> String?
  {
      var theResult:String?
      let startAtLoginScript: NSAppleScript = NSAppleScript(source: script)!
      var errorInfo:NSDictionary? = nil
      let theDiscriptor:NSAppleEventDescriptor = startAtLoginScript.executeAndReturnError(&errorInfo)
      if let _ = theDiscriptor.stringValue {theResult = theDiscriptor.stringValue!}
      return theResult
  }
  

  Bonus

  通过返回可选字符串，它允许您检查代码是否返回了值 .

  例：

  Old way

  let output = runAppleScript("script")
  if output != ""
  {
      //Script returned date
  } else {
      //Script did not return data
  }
  

  New way

  if let output = runAppleScript("script")
  {
      //Script returned data
  } else {
      //Script did not return data
  }
  

  回复于 2024-05-04T07:55:45+08:00