ANSWER BELOW
Im facing a little issue that you may help me with.
the app Im working on allows you to request for content based on your location.
the first ViewController is somewhat a form that grab your location / a specified location + some other information to target specific answers.
I need to perform a segue to pass the "question" variables to my second ViewController where I load "answers" with a query based on the question details.
What is causing me trouble is that, whenever the question is geolocalized, I can't retrieve the information using prepareForSegue because it doesn't wait for the geoPoint to be made (completed).The second controller display my latitude and longitude as nil.
I see that I can call the "prepareForSegue" method using "perfomSegueWithIdentifier", and retrieve the information in my second view controller but it perform the segue twice... How can I trigger the segue only when Im ready but using the prepareForSegue data parameter I need to preserve?
Is there a way to pass variable from one controller to another using performSegue?
Any help would be awesome.
Also, while I don't think the code is relevant for my question, here is the code I use.
geoPointing method
#IBAction func doPostQuestion(sender: UIButton) {
var thereQ:PFObject = PFObject(className: "tquestion")
if(somewhereLabel.text == "my location"){
println("Location is geolocalized")
PFGeoPoint.geoPointForCurrentLocationInBackground {
(geoPoint: PFGeoPoint!, error: NSError!) -> Void in
if error == nil {
self.geoLati = geoPoint.latitude as Double
self.geoLong = geoPoint.longitude as Double
self.performSegueWithIdentifier("goto_results", sender:self) // call prepareForSegue when ready but implies to have a segue done on click... (performed twiced)
}
}
}
self.navigationController?.popToRootViewControllerAnimated(true)
}
prepareForSegue
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if(segue.identifier == "goto_results"){
// Get Label
let theDestination = (segue.destinationViewController as displayAnswersViewController)
theDestination.lat = self.geoLati
theDestination.lng = self.geoLong
}
}
ANSWER SOLUTION:
As suggested, to solve this problem you just need to create your segue from your viewController1 to your viewController2 and not from a button. This way you can trigger prepareForSegue programatically using the "performSegue" method that will call prepareForSegue anyway.
To solve this problem you just need to create your segue from your viewController1 to your viewController2 and not from a button. This way you can trigger prepareForSegue programatically using the "performSegue" method that will call prepareForSegue anyway.
Related
I'm trying to pass data from a SecondViewController to my FirstViewController when I click on my back button (UINaviagtionController).
For pass my data from FirstViewController to the SecondViewController I do this:
if segue.identifier == "showSecondVC" {
let vc = segue.destination as! SecondViewController
vc.rows = rows[pathForAVC]
vc.lap = lapTime[pathForAVC]
vc.indexPath = pathForAVC
}
But I have no idea how to pass data from SecondViewController to the FirstViewController and I really don't understand topics about it on Stack Overflow.
I want to transfer it when I click here:
Thanks.
You can use delegate pattern for that. You can grab the back button press event like this and update the data
override func viewWillDisappear(_ animated: Bool) {
if self.isMovingFromParentViewController {
self.delegate.updateData( data)
}
}
For more information on delegates you can go through this.
Actually things depend on your requirement, if you want data to be updated in first view controller as soon as it is updated in second view controller, you would need to call delegate as soon as the data is updated. But as in the question you have mentioned that you want it to be updated on back button only, above is the place to do it.
Another way would be to have Datasource as singleton so that it is available to all the view controllers and the changes are reflected in all view controllers. But create singleton if absolutely necessary, because these nasty guys hang around for entire time your application is running.
You should have a custom protocol such as:
public protocol SendDataDelegate: class {
func sendData(_ dataArray:[String])
}
Here I suppose you want to send a single array back to FirstViewController
Then make your first view controller to conform to the custom protocol, such as:
class FirstViewController: UIViewController, SendDataDelegate
In the second view controller, create a delegate a variable for that protocol, such as:
weak var delegate: SendDataDelegate?
and then you catch the back action and inside it you call your custom protocol function, such as:
self.delegate?.sendData(arrayToSend)
In the first viewController, in the prepare for segue function just set the delegate like
vc.delegate = self
So i am new to app development and i am trying to set up a very simple delegation/protocol pattern. I have been searching and trying different tutorials but can't seem to find anything that works and am getting in such a muddle. Please can somebody help. I will break i down so that its really clear as to what i need -
I have two view controllers, 'DetailedVC' and 'SelectionsVC'.
DetailedVC has a variable called -
var sendingData = (choice: "", choiceValue:0.0)
and
UIbutton buttonSelectTapped
SelectionsVC has a variable called -
var recievedData = (choice: "", choiceValue:0.0)
And all i want to do is send the data from the variable 'sendingData' in DetailedVC when the button (buttonSelectTapped) is tapped to the SelectionsVC and store it in the variable 'recievedData'. I do not want the VC to transition from one to the other or anything to be sent back, only to send the data to the other VC.
Then when the user views that controller 'SelectionsVC' at whatever stage, the data will be called in the viewDidLoad when loading that controller.
Use NSUserDefault to pass data between viewcontroller if you do not want the VC to transition from one to the other or anything to be sent back, only to send the data to the other VC.
DetailedVC Code
func viewDidLoad() {
NSUserDefaults.standardUserDefaults().removeObjectForKey("selectedData")
}
func didTapButtonSelectTapped() {
NSUserDefaults.standardUserDefaults().setDouble(sendingData , forKey: "selectedData")
}
SelectionsVC code
func viewDidLoad() {
if(NSUserDefaults.standardUserDefaults().doubleForKey("selectedData")) {
recievedData = NSUserDefaults.standardUserDefaults().doubleForKey("selectedData")
}
}
But as your question title describe their is no use of protocol/delegate in above code.
Passing Data on transition from viewcontroller :
DetailedVC Code
func didTapButtonSelectTapped() {
let vc = SelectionsVC()
vc.recievedData = sendingData
self.presentViewController(vc, animated: true, completion: nil)
}
I am using the QR code reader code from AppCoda (http://www.appcoda.com/qr-code-reader-swift/#comments) and converted it to Swift 3. The base code works perfectly fine.
However, what I want to achieve is to retrieve a String from the QR reader, store it in a variable, and pass the variable to a following view controller. So I added a bit of code to it to get the following:
func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputMetadataObjects metadataObjects: [Any]!, from connection: AVCaptureConnection!) {
if metadataObjects == nil || metadataObjects.count == 0 {
qrCodeFrameView?.frame = CGRect.zero
messageLabel.text = "No barcode/QR code is detected"
return
}
let metadataObj = metadataObjects[0] as! AVMetadataMachineReadableCodeObject
if supportedBarCodes.contains(metadataObj.type) {
let barCodeObject = videoPreviewLayer?.transformedMetadataObject(for: metadataObj)
qrCodeFrameView?.frame = barCodeObject!.bounds
if metadataObj.stringValue != nil {
messageLabel.text = metadataObj.stringValue
}
//
//
// CODE I ADDED STARTS BELOW
//
performSegue(withIdentifier: "showMenu", sender: self)
}
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "showMenu"{
let tabVc = segue.destination as! UITabBarController
let navVc = tabVc.viewControllers?.first as! UINavigationController
let menuVc = navVc.viewControllers.first as! MenuViewController
menuVc.qrScan = self.messageLabel.text
}
It actually achieves what I wanted it to do, but it somehow triggers the "performSegue" multiple times. The transition animation of the first segue goes halfway, and then the second one happens.
The segue "showMenu" is a manual segue connected from the view controller of the QR Reader view to a tab bar controller that houses a navigation controller and Menu view controller.
Things I've tried:
Print the passed on variable in the viewdidload function of Menu view controller. The string gets printed out twice.
Added a hidden button on the QR reader view and change the segue connection of "showMenu" from the view controller to the button. Removed perform segue from code. While holding the camera in place to scan qr codes, pressing the button performs the intended function and the segue is only triggered once.
With the same setting as (2), I programmatically trigger the button by using a touch up inside event when a qr code is scanned. The segue gets triggered twice.
Added breakpoints for performSegue and the if clause right above it. After I scan something, and press the "continue program execution" button, the program loops between the two breakpoints on and on.
If anyone can enlighten me a bit over here, I would be very grateful. Thanks a bunch for the help in advance.
The issue was fixed by adding the following line of code after the segue was performed:
self.captureSession?.stopRunning()
However, the question of why doesn't unwind segue have a similar issue still remains.
I've just solved the same problem. You have to create an unwind to the previous view.
To do this in the interface builder, you have to ctrl-drag from the controller to the exit in the controller you're actually in (not the one you want to unwind).
Once you have done this, you have to set an identifier to this unwind segue (in your case "showMenu". To do this, you have to the unwind segue from the scenes menu on the left part and set the identifier name on the Attributes inspector.
Currently I have the application loading up the data in a tableview presented to the user that I want them to select the object they wish to view further details about. From their I want to be able to read out the data in the object to the user in various forms either labels or a tableview dependent on the data.
I have been reading around and trying to understand this stuff but it is all still new to me! I had another guy on here help me out with saving the data and passing the data around to store but reading it out is a seemingly different thing. Any examples in swift language would lead me down the right path I know that I need to use the didselectrow method and call a segue and also that I need a prepare for segue but I am not quite sure how it should look.
I have read multiple posts and some do actually attempt to pass objects but not in the manner in which I am trying to..Are you able to pass whole objects after they have been have been selected in a tableview to another view controller to present all data related to that object or are you only able to pass information from that object to the next viewcontroller? I have examples of prepareforsegue and perform segue before not sure what else I am missing but I am currently not able to pass any information between the tableview and the viewcontroller.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!) {
if (segue.identifier == "decktoRecord") {
var detailVC: StatWidgetViewController = segue.destinationViewController as! StatWidgetViewController
detailVC.deckRecord = decktoPass
}
}
func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
let indexPath = tableView.indexPathForSelectedRow()
let selectedCell = tableView.cellForRowAtIndexPath(indexPath!) as UITableViewCell?
self.performSegueWithIdentifier("decktoRecord", sender: indexPath);
}
decktoPass is just a variable that contains the type of data entity that is the primary entity of the object.
A little confused by what you're asking but from what I understand, once the user clicks on a cell you want to segue to another view controller where they can edit the the details?
To add an exception breakpoint, open up your left panel with all your files/viewcontrollers, at the very top of it should be a small panel with a few icons, the first one is a folder, click on the second last one (the one that looks like a tag)
click on the plus in the bottom right and click add exception breakpoint, this should let you know where the problem in your code is occurring
Okay to edit the details in another View controller start by preparing the segue from the original view controller
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "showTaskDetail" {
let detailVC: TaskDetailViewController = segue.destinationViewController as! TaskDetailViewController
let indexPath = self.tableView.indexPathForSelectedRow()
let thisTask = fetchedResultsController.objectAtIndexPath(indexPath!) as! TaskModel
detailVC.detailTaskModel = thisTask
detailVC.delegate = self
}
else if segue.identifier == "showTaskAdd" {
let addTaskVC:AddTaskViewController = segue.destinationViewController as! AddTaskViewController
addTaskVC.delegate = self
}
}
okay so like the code is showing above, I have a segue called showTaskDetail which shows the details of whatever it is, in my case its a simple task. You said you want to edit this information in another view controller when a user clicks on the row, well you need to be able to get this information in the other view controller.
So create a variable in the other viewcontroller that will hold these values, for me i called it detailTaskModel
var detailTaskModel: TaskModel!
Incase you're confused about what TaskModel is, I'm using CoreData to store my data, and TaskModel is a NSMangedObject class.
let detailVC: TaskDetailViewController = segue.destinationViewController as! TaskDetailViewController
this line you're just specifying what your other view controller is, replace TaskDetailViewController with your swift class.
let detailVC: TaskDetailViewController = segue.destinationViewController as! TaskDetailViewController
this line fetches the data from the row selected
Now you should be able to pass your information into the other view controller and edit it using the detailTaskModel, do you need help with that as well?
Big problem here guys, I'm on the verge of finishing my blog project until I came across a segue issue, I'm trying to display the contents of a blogs web view on a uiwebview in another controller. This is my first time working with MediaRSS and AFNetworking. I have been able to parse the contents before, but am having no luck this time around. All help is greatly appreciated. I keep getting NSIndexPath is not a member of PostLink
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "viewpost" {
let indexPath = tableView.indexPathForSelectedRow()
let item = items[indexPath!.row]
let detailViewController = segue.destinationViewController as PostViewController
detailViewController.postLink = indexPath.postLink
}
}
}
UPDATE 9:17PM
Looks like im performing a segue properly, because now my page will go to a blank. Can someone please confirm the parameters I am passing in, I just need someone to look and tell me please
NSIndexPath does not have any member named postLink. I think you mean to write item.postLink.
detailViewController.postLink = item.postLink
I hope item is of some type that has 'postLink' member and it is populated with appropriate value.