ios - prepareForSegue 在 performSegue 之前调用

Question

我正在尝试执行一个 segue，将多个变量传递到下一个 View ，包括一个变量 currentID，它是从解析数据库中检索到的。在将 currentID 设置为从数据库下载的 currentID 之前，不应调用 performSegue。但是，当我运行代码时，当 currentID 传递给下一个 View 时，它最终变成了一个空字符串。

这是我的按钮调用的代码:

@IBAction func submitButtonPressed(_ sender: Any) {

    let point = PFGeoPoint(latitude:0.0, longitude:0.0)
    let testObject = PFObject(className: "Person")

    testObject["inputAmount"] = inputAmount
    testObject["outputAmount"] = outputAmount
    testObject["inputCurrency"] = inputCurrency
    testObject["outputCurrency"] = outputCurrency
    testObject["location"] = point

    testObject.saveInBackground { (success, error) -> Void in

        // added test for success 11th July 2016

        if success {
            print("Object has been saved.")

            self.currentID = String(describing: testObject.objectId!)
            if(self.currentID != ""){
                self.performSegue(withIdentifier: "mainToListSegue", sender: self)
            }

        } else {
            if error != nil {
                print (error)
            } else {
                print ("Error")
            }
        }
    }
}

这里是 prepareForSegue 方法:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    let listViewController = (segue.destination as! UINavigationController).viewControllers[0] as! ListViewController
    listViewController.inputCurrency = inputCurrency
    listViewController.outputCurrency = outputCurrency
    listViewController.inputAmount = inputAmount
    listViewController.outputAmount = outputAmount
    listViewController.currentID = currentID
    listViewController.cellContent = cellContent
}

Answer 1

为了满足您的需求，您必须在 View Controller 之间连接您的 segue，而不是从 UIButton 到 View Controller 。

每次你需要在调用之前准备你的 segue 时，程序如下:

然后，命名并使用委托(delegate)方法

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    if segue.identifier == "mySegue" {

    }
}