NSAlert - 如何在 Swift3 中将视图呈现为 sheet 并获得 return 值？

Question

我有以下代码工作正常：

 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

我这样检查 NSAlertFirstButtonReturn 的值：

 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 sheet。

我不知道如何呈现和测试结果。我目前得到的全是真或全是假。

我已经尝试了各种排列，例如下面的排列，但并不愉快，如果有任何帮助，我将不胜感激。

//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 return 来自包含异步任务的函数/方法的值。

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
            }
        })
    }
}

功能几乎相同，但执行是异步的。

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

NSAlert - 如何在 Swift3 中将视图呈现为 sheet 并获得 return 值？

NSAlert - how can I present a view as a sheet and get a return value in Swift3?

cocoa

swift3

macos-sierra