ios - 为什么我不能在我的prepareForSegue方法中快速转换发送者？

Question

我的应用程序中有一个 ListView ，我正在动态添加单元格。对于每个单元格，我想附加一个segue，并感谢它在用户按下单元格时打开一个UIViewController(称为FullUser)(该UIViewController将包含此segue传递的数据，从所选的特定单元格获取)由用户存储在名为 SingleUser 的结构中)。所以我有这个方法:

override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
    var cell: UITableViewCell = tableView.cellForRowAtIndexPath(indexPath) as! SingleEventCell

    let user =  self.items[indexPath.row] as? SingleUser

    self.performSegueWithIdentifier("fullUserFromListSegue", sender: user)
    }

然后:

var fullUserDetails: FullUser?

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
     if (segue.identifier == "fullUserFromListSegue"){

        fullUserDetails = segue.destinationViewController as? FullUser

       //now I want to set the textfield on the other panel:

        let user2 =  sender as? SingleUser

        var username = user2?.username

        fullRequestDetails!.username.text = username!
    }
}

但是我收到错误，当我在调试器中检查它时，我发现 user2 为零。为什么这样？我想在那里存储一个 SingleUser 对象，那么如何将它传递到那里呢？

Answer 1

将逻辑移至 prepareForSegue() 函数中，然后在目标 View Controller 上设置属性。请注意，如果 destinationViewController 不属于您期望的类，那么您应该检查 Storyboard中的 View Controller 设置。

var fullUserDetails: FullUser?

override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
    // check the destintation view controller is of correct class        
    if let fullUserDetails = segue.destinationViewController as? FullUser {
        let path = self.tableView.indexPathForSelectedRow
        let user =  self.items[path.row] as? SingleUser

        var username = user?.username

        fullRequestDetails!.username.text = username!
    }
}