Swift：在视图之间传递变量不会第一次更新

Question

I have a tableview with cell data. When I click the cell, it takes me to another view controller and displays the cell label in a UIlabel on the new ViewController.

However, When I go back to the tableview and select a different cell, the value on the new view controller doesn't update immediately. It displays the last clicked cell, then if I go back and repeat the process a second time it will update.

didSelectRowAtIndexPath

override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
    let currentCell = tableView.cellForRowAtIndexPath(indexPath)! as UITableViewCell

    self.labeltosend = currentCell.textLabel!.text!
}

prepareForSegue

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == PostSegueIdentifier {
        if let destination = segue.destinationViewController as? NewViewController {
            destination.newlabel = labeltosend
        }
    }
}

Am I supposed to reload the data somehow?

edit 1: Destination View Controller

@IBOutlet weak var dispLabel: UILabel!
var newlabel = String()

override func viewWillAppear(animated: Bool) {
    dispLabel.text = newlabel
}

override func viewDidLoad() {
    super.viewDidLoad()
    // Do view setup here.

}

Answer 1

prepareForSegue(_:sender) is not called if you draw segue from cell to next view controller. Try to draw segue from view controller to view controller. And perform a manual segue using performSegueWithIdentifier("MySegueIdentifier" sender:self) in tableView(_:didSelectRowAtIndexPath:indexPath) . For more info please have a look at this answer .

Answer 2

Think prepareForSegue is sometimes getting called before didSelectRowAtIndexPath you can move that code to prepareForSegue. When you set up a segue as you have sender in prepareForSegue is the indexPath of row tap, precisely so you can do these sorts of things.

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == PostSegueIdentifier {
        if let destination = segue.destinationViewController as? NewViewController {
            let indexPath = sender as NSIndexPath
            let currentCell = tableView.cellForRowAtIndexPath(indexPath)! as UITableViewCell

            self.labeltosend = currentCell.textLabel!.text!
            destination.newlabel = labeltosend
        }
    }
}

You should read Duncan's comment.

Answer 3

First: if you have your segue connected from the UITableViewCell, don't. Delete it and connect the segue from the view controller itself.

Second: on the didSelectRowAtIndexPath method, call prepareForSegue method.

And finally on the destination controller:

@IBOutlet weak var dispLabel: UILabel!
var newlabel = String()

override func viewWillAppear(animated: Bool) {
    //dispLabel.text = newlabel
}

override func viewDidLoad() {
    super.viewDidLoad()
    // Do view setup here.
    dispLabel.text = newlabel

}

Also, you need to improve your naming convention. Is really confusing

Hope this helps!