I tried to pass the value of the cell that the user clicks on to another view controller.
Here is my code.
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
productDisplayed = currentProductList[indexPath.row] as? Product
performSegue(withIdentifier: "ProductDetailSegue", sender: self)
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if ( segue.identifier == "AddProductSegue"){
let controller: AddProductViewController = segue.destination as! AddProductViewController
controller.delegate = self
}
if ( segue.identifier == "ProductDetailSegue"){
let controller: ProductDetailsViewController = segue.destination as! ProductDetailsViewController
controller.currentProduct = productDisplayed
}
}
Firstly, I didn’t write “performSegue()”.
The issue I met is that the screen will be transferred firstly rather than assign the value to “productDisplayed”, which means the object “currentProduct” in the second VC is nil.
Then I added “performSegue()”.
It still didn’t work. The thing is the second screen was displayed twice. The first time is same with the picture above. And the second time is correct.
But when I tried to click the back button on the left top. It returned to the nil page rather than the ProductDetail page. The screenshot is as follows.
It seems like "prepare" method always being called first then the tableView. How to change the order? If can, this should be fixed I think.
Hope to get your help.
Thank you.
Cause of Problem:
In your storyboard, you may have bound, ProductDetailsViewController with UITableViewCell directly.
It means, upon click/selection of row, it will perform segue (navigation) operation directly.
At the same time, programatically you perform navigation operation using performSegue(withIdentifier: "ProductDetailSegue", sender: self)
Solution:
You have two ways to solve this issue.
I recommend - In your story board, switch segue connection from UITableViewCell to UIViewController (Remove segue connection from UITableViewCell and attach the same segue connection with UIViewController of your tableview)
In your source code, delete/remove this line performSegue(withIdentifier: "ProductDetailSegue", sender: self) and handle data transmission from this function override func prepare(for segue: UIStoryboardSegue, sender: Any?)
Related
I have a UIViewController which should show me DetailInformations depending on what Cell was pressed in the UITableViewController.
For the moment I am passing them through a sequel:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "show" {
var ctrl = segue.destination as! DetailViewController
ctrl.information = _informationList[id]
}
}
The id variable is set through:
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
id = indexPath.row
}
Now in my UIViewController I change the information with:
override func viewDidLoad() {
super.viewDidLoad()
setInformation(i: information)
}
Now my problem is, that if I press, lets say cell 2. It switches to the ViewController and shows Information of cell 1. Than I go back to the tableview and I press cell 3. Then it shows me cell 2.
In short, it seems that the viewController is loaded (with the last information), before it sets the new information.
Is there any better way to solve this?
Try using indexPathForSelectedRow in prepareForSegue as of it looks like that you have created segue from UITableViewCell to the Destination ViewController so that prepareForSegue will call before the didSelectRowAt.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "show" {
var ctrl = segue.destination as! DetailViewController
if let indexPath = self.tableView.indexPathForSelectedRow {
ctrl.information = _informationList[indexPath.row]
}
}
}
I am assuming based on what you are describing is that you used a segue in your Storyboard to link directly from the cell to the detail view controller. This is not what you want to do, as mentioned earlier, because you don't get the order of events you would expect. You could use the delegation design pattern for this, but assuming you want to stick with segues you need to make the "show" segue from the table VC itself to the detail VC. You then manually call the segue from the tableView didSelectRowAt code.
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
id = indexPath.row
performSegue(withIdentifier: "show", sender: self)
}
Finally, you could then use an unwind segue when you come back to catch any data changes initiated in the detail VC.
I have two segues from one ViewController.
One is supposed to run(crashes for now) when clicking on LogOut Button (Go to LogIn ViewController), another one runs(works good) when clicking on thumbnail of a video.
Since I need to retrieve the video from the server and display it in the ViewController I'm heading to(WatchVideoViewController), I do the code below:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
// Get a reference to a destination View Controller
let detailViewController = segue.destinationViewController as! WatchVideoViewController
// Set the selected video property of the destination view controller
detailViewController.selectedVideo = self.selectedVideo
}
As you might guess this code runs when performing every segue, that's why my LogOut segue crashes.
Could not cast value of type 'AppName.LoginViewController' to 'Appname.WatchVideoViewController'.
Here are pieces of code where I call segues:
#IBAction func pressLogOutButton(sender: AnyObject) {
self.performSegueWithIdentifier("logOutSegue", sender: self)
}
// Handle event when user selects a cell(thumbnail)
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
// Take note of which video is selected
self.selectedVideo = self.videos[indexPath.row]
// Call the segue
self.performSegueWithIdentifier("goToVideo", sender: self)
}
Is there any way to avoid running prepareForSegue when calling pressLogOutButton? Thanks a lot!
Check in your prepareForSegue
if segue.identifier == "logOutSegue"
// perform log out logic
I am populating a table view as menu using a custom table view cell and using it as menu.I am able to navigate to other views using navigation controller.
But I want to create views and its controls programmatically. Is it possible?
Can anyone please share me an example. Please find my menu structure in the following image.
This is how i did it. It works like a charm!!!
func tableView(_tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
//Remove the below line from this function as it will perform segue.
//performSegue(withIdentifier: "DynamicSegue", sender: self)
}
override func prepare(for segue: UIStoryboardSegue, sender: AnyObject?) {
// This will actually perform your segue
var DestViewController = segue.destination as! DynamicSuperView
let selectedRow = tableView.indexPathForSelectedRow?.row
DestViewController.labelText = names[selectedRow!]
}
i am trying to build my first iOS app with swift. I am stuck at a segue where i want to give the row indexpath to the next page, but the indexpath is "optional(0)" instead of "0". does anyone know why? in the code, there's a print sender. That one says "optional(0)" The variable "viewController.passedValue" is set to 0, the real code is behind it in comments
does anyone know why it gives "Optional(0)"?
Code:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let viewController = segue.destinationViewController as! NewsDetailViewController
print(String(sender))
viewController.passedValue = 0 // sender as! int
}
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
performSegueWithIdentifier("DetailSegue", sender: indexPath.row)
print("HIER")
}
You are calling
performSegueWithIdentifier("DetailSegue", sender: indexPath.row)
And then, iOS is calling your prepareForSegue, in which sender is defined as an AnyObject?, i.e. an optional AnyObject:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
...
}
Thus, when you print sender, it's an optional and thus informs you of such. If you don't want the optional, you could unwrap it (either forced unwrapping or, better, optional binding).
--
As an aside, though, it is a misuse of sender to be storing the indexPath.row there. As the documentation for performSegueWithIdentifier says, the sender is:
The object that you want to use to initiate the segue. This object is made available for informational purposes during the actual segue.
But indexPath.row is not the object that initiated the segue (the table view cell is). I therefore would advise against using the sender to hold the indexPath.row. A more common pattern would be
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if let destination = segue.destinationViewController as? NewsDetailViewController, let row = tableView.indexPathForSelectedRow?.row {
destination.passedValue = row
}
}
This also has the virtue of giving you the alternative of not defining a didSelectRowAtIndexPath at all, and just represent your segue from the storyboard's cell prototype directly to the NewsDetailViewController scene. If you really want to segue programmatically, you can do that, but it's not necessary. But I would not advise using sender to represent the indexPath.row, but rather the UI control that triggered the segue.
i recently made a tableview filled with cells. i was wondering if i can, when i tap a cell display a certain picture instead of a blank screen
i tried linking cells with different image views but i can't do that using a tableview ,so what is the required code
i do know that I'm supposed to use the prepareForSegue statement
override prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {}
i just don't know what to type
i only want to add an image display when i tap one of the cells
thanks for the help
You have to add another view controller in your storyboard which will be opened after tapping the cell.
In tableView(_:didSelectRowAtIndexPath:) you have to remember which cell was tapped, and in prepareForSegue you can pass data to the destination view controller. In destination view controller just load the image based on data passed.
You can use prepareForSegue to pass data from your cell to the next ViewController (the image one).
I would do something similar to this.
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
self.indexTapped = indexPath.row
self.performSegueWithIdentifier("goToImageViewController", sender: self)
}
....
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if (segue.identifier == "goToImageViewController") {
var vc = segue.destinationViewController as! ImageViewController
vc.image = imageDatasource[indexTapped] as! UIImage
}
}
Once you call performSegueWithIdentifier(identifier: String?, sender: AnyObject?) the transition will be automatically handled after executing the prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) code.