Linking tableview cell information to a view controller - swift

Question

I'm pretty new to Swift. I wish to reflect tableview cell data (title and description of a post) in a new view controller. Here's the code I put in the first view controller (which contains the tableview cell).
func tableView(tableView: UITableView!, didSelectRowAtIndexPath indexPath: NSIndexPath!) {
let indexPath = tableView.indexPathForSelectedRow()!
let currentCell = tableView.cellForRowAtIndexPath(indexPath) as! PostCell!
let post = posts[indexPath.row]
valuetoPass = post.title
valuetoPass_desc = post.postDescription
performSegueWithIdentifier("seguetoVC", sender: self)
}
And this one...
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "seguetoVC" {
let viewController = segue.destinationViewController as! UpdateVC
viewController.toPassTitle = valuetoPass
viewController.toPassDesc = valuetoPass_desc
}
}
Here's a part of UpdateVC..Added the variables, toPassTitle and toPassDesc...And these are the lines I added to viewDidLoad():
override func viewDidLoad() {
super.viewDidLoad()
self.postTxt.delegate = self
self.descTxt.delegate = self
descTxt.text = toPassTitle
postTxt.text = toPassDesc
}
Just wondering what I'm doing wrong-- viewController.toPassTitle and viewController.toPassDesc keep on returning a null value. Thanks in advance.

Answer 1

You can set the sender parameter to be whatever type you want, there's no reason for it to be self, i.e. the originating view controller if that's not what you need. In fact, there should never be a need to pass the originating view controller as the sender, because you can get it from segue.sourceViewController in prepareForSegue.
In the documentation for prepareForSegue, Apple suggests:
Because segues can be triggered from multiple sources, you can use the information in the segue and sender parameters to disambiguate between different logical paths in your app. For example, if the segue originated from a table view, the sender parameter would identify the table view cell that the user tapped. You could then use that information to set the data on the destination view controller.
Which sounds like exactly the situation you're in. Since you've already figured out the model object for your cell, we can pass that rather than the cell. So, you could call performSegueWithIdentifier("seguetoVC", sender: post), and then change up your prepareForSegue implementation to use the details from the post directly, e.g.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "seguetoVC" {
let viewController = segue.destinationViewController as! UpdateVC
if let post = sender as ? Post {
viewController.toPassTitle = post.title
viewController.toPassDesc = post.postDescription
}
}
}
You don't need to call tableView.cellForRowAtIndexPath(indexPath) as! PostCell! anywhere, and it could be fairly expensive, so don't do it if you don't use it. Your didSelectRowAtIndexPath method might look more like this:
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
let post = posts[indexPath.row]
performSegueWithIdentifier("seguetoVC", sender: post)
}
There's also a bunch more you could do to make it safer, so have a look at unwrapping optionals using constructs such as if let and guard let, which can also help you avoid force casting (!), and potentially crashing your app. I've done that in unwrapping sender to post, so you can see an example there.

Answer 2

You do not need to declare indexPath again. didSelectRowAtIndexPath already has indexPath. Update your codes in didSelectRowAtIndexPath method.
func tableView(tableView: UITableView!, didSelectRowAtIndexPath indexPath: NSIndexPath!) {
let post = posts[indexPath.row]
valuetoPass = post.title
valuetoPass_desc = post.postDescription
performSegueWithIdentifier("seguetoVC", sender: self)
}
On top of that, ensure that in your storyboard, you need to name your segue identifier with seguetoVC also.