如何將更多參數傳遞給 UIAlertAction 的處理程序？

Question

有沒有辦法將數組“listINeed”傳遞給處理程序 function“handleConfirmPressed”？ 我能夠通過將它添加為 class 變量來做到這一點，但這看起來很老套，現在我想對多個變量這樣做，所以我需要一個更好的解決方案。

func someFunc(){
   //some stuff...
   let listINeed = [someObject]

   let alert = UIAlertController(title: "Are you sure?", message: alertMessage, preferredStyle: UIAlertControllerStyle.Alert)
   alert.addAction(UIAlertAction(title: "Cancel", style: .Cancel, handler: nil))
   alert.addAction(UIAlertAction(title: "Confirm", style: .Destructive, handler: handleConfirmPressed))
   presentViewController(alert, animated: true, completion: nil)
}

func handleConfirmPressed(action: UIAlertAction){
  //need listINeed here
}

Answer 1

最簡單的方法是將一個閉包傳遞給UIAlertAction構造函數：

func someFunc(){
    //some stuff...
    let listINeed = [ "myString" ]

    let alert = UIAlertController(title: "Are you sure?", message: "message", preferredStyle: UIAlertControllerStyle.Alert)
    alert.addAction(UIAlertAction(title: "Cancel", style: .Cancel, handler: nil))
    alert.addAction(UIAlertAction(title: "Confirm", style: .Destructive, handler:{ action in
        // whatever else you need to do here
        print(listINeed)
    }))
    presentViewController(alert, animated: true, completion: nil)
}

如果您真的想要隔離例程的功能部分，您可以隨時放置：

handleConfirmPressedAction(action:action, needed:listINeed)

進入回調塊

稍微更模糊的語法，在將函數傳遞給完成例程和回調函數本身時都會保留函數的感覺，將handleConfirmPressed定義為curried函數：

func handleConfirmPressed(listINeed:[String])(alertAction:UIAlertAction) -> (){
    print("listINeed: \(listINeed)")
}

然后你可以使用addAction ：

alert.addAction(UIAlertAction(title: "Confirm", style: .Destructive, handler: handleConfirmPressed(listINeed)))

請注意，curried函數是以下的簡寫：

func handleConfirmPressed(listINeed:[String]) -> (alertAction:UIAlertAction) -> () {
    return { alertAction in
        print("listINeed: \(listINeed)")
    }
}

Answer 2

我認為這更容易。

class MyUIAlertAction: UIAlertAction {
    var params: [String: Any] = [:]
}

func someFunc(){
    //some stuff...
    let listINeed = [ "myString" ]
    
    let alert = UIAlertController(title: "Are you sure?", message: "message", preferredStyle: .alert)
    alert.addAction(UIAlertAction(title: "Cancel", style: .cancel, handler: nil))
    
    let action =  MyUIAlertAction(title: "Confirm", style: .destructive, handler:{ (action: UIAlertAction) in
        if let myaction = action as? MyUIAlertAction {
            let listINeed = myaction.params["listINeed"] as? [String] ?? []
            // whatever else you need to do here
            print(listINeed)
        }
    })
    action.params["listINeed"] = listINeed
    
    alert.addAction(action)
}