斯威夫特：如何传递子视图控制器prepareForSegue的数据以更改父视图控制器表视图单元格的TextLabel？

Question

How can I pass data from child viewcontroller prepareForSegue to change Title of a cell of parent viewcontroller tableview?

I have done it this way, but I don't think it's right:

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) 

{
    if segue.identifier == "unwindToCreateTask" {
        let contact = contactList[self.tableView.indexPathForSelectedRow()!.row]

        let destinationVC = segue.destinationViewController as! CreateTaskVC

        destinationVC.tableView.reloadData()

        if let destinationCell = destinationVC.tableView.dequeueReusableCellWithIdentifier("assignToCell") as? UITableViewCell {
            destinationCell.textLabel?.text = contact.contactName
            destinationCell.detailTextLabel?.text = contact.contactEmail
        }
    }
}

Answer 1

Your child view controller should not know about the implementation of its parent. You are reaching into the table view of the parent from the child, but it would be more correct for the parent to access the required data from the child. Unwind segues allow you to do this by defining an unwind method in the parent.

In your parent , you define an @IBAction method that takes a single UIStoryboardSegue parameter. This is called on the parent at the start of the segue, and allows you to "pass back" any data to the parent in a way that prevents the need for delegation. A UIStoryboardSegue has a sourceViewController property, so in the case of an unwind segue, the child is the source.

@IBAction func unwindToParent(segue: UIStoryboardSegue) {
    if let childVC = segue.sourceViewController as? ChildVC {
        // update this VC (parent) using newly created data from child
    }
}

After defining the method, you create the segue in your storyboard by control-dragging from the triggering element in your child scene to the "exit" icon at the top of that scene. From the menu that appears, choose the unwind action you just created in the parent.