cocoa - NSAlert - 如何将 View 呈现为工作表并在 Swift3 中获取返回值？

Question

我有以下代码可以正常工作:

 func alertDialog(question: String, text: String) -> Bool {
    let alert: NSAlert = NSAlert()
    alert.messageText = question
    alert.informativeText = text
    alert.alertStyle = NSAlertStyle.warning
    alert.addButton(withTitle: "Yes Please")
    alert.addButton(withTitle: "No Thank You")
     changedItem = false
  return alert.runModal() == NSAlertFirstButtonReturn

我检查 NSAlertFirstButtonReturn 的值，如下所示:

 func tableViewSelectionDidChange(_ notification: Notification)
    {
        print (#function, "changedItem", changedItem!)
        if changedItem == true {
            let answer = alertDialog(question: "Save your changes?", text: "Unsaved changes will be shredded.")
            print(#function, "answer: ", answer)
            if answer == true {
                print(#function, "TRUE")
                saveChanges(self)
                changedItem = false
            }
        }

我正在努力执行相同的功能，但将警报显示为表格。

我不知道如何呈现和测试结果。我目前的判断要么全对，要么全错。

我尝试了各种排列，如下所示，但没有任何乐趣，并且希望得到任何帮助。

//instead of the return sheetModal

        var result: Int! = 0
        //result = false
        alert.beginSheetModal(for: self.view.window!, completionHandler: { (NSAlertFirstButtonReturn) -> Void in
            if NSAlertFirstButtonReturn.hashValue  == 1000 {
                result = 1
            } else {
                result = 0
            }


        })
         print(#function, "NSAlertFirstButtonReturn: ", NSAlertFirstButtonReturn.hashValue)
        changedItem = false

        if result == 1 {
            return true
        } else {
            return false
        }

Answer 1

与 runModal 方法不同，beginSheetModal(for:completionHandler:) 异步工作。不可能从包含异步任务的函数/方法返回值。

向 alertDialog 方法添加完成处理程序:

func alertDialog(question: String, text: String, completion: @escaping (Bool)->() ) {
    let alert: NSAlert = NSAlert()
    alert.messageText = question
    alert.informativeText = text
    alert.alertStyle = NSAlertStyle.warning
    alert.addButton(withTitle: "Yes Please")
    alert.addButton(withTitle: "No Thank You")
    changedItem = false
    alert.beginSheetModal(for: self.view.window!, completionHandler: { result in
        completion(result == NSAlertFirstButtonReturn)
    })
}

并使用方法:

func tableViewSelectionDidChange(_ notification: Notification)
{
    print (#function, "changedItem", changedItem!)
    if changedItem == true {
        alertDialog(question: "Save your changes?", text: "Unsaved changes will be shredded.", completion: { [unowned self] answer in
            print(#function, "answer: ", answer)
            if answer == true {
                print(#function, "TRUE")
                self.saveChanges(self)
                self.changedItem = false
            }
        })
    }
}

功能实际上相同，但执行是异步的。

旁注:为什么 changedItem 是可选的？它似乎是一个真正的 Bool，只有两个状态。