swift conditionally call unwind segue using shouldPerformSegue - ios

Question

I have two view controllers: Step3VC (we'll call this 'A') and Step3AddJobVC (we'll call this 'B'). I'm trying to validate some data on 'B' before performing an unwind segue back to 'A'.
'B' takes some user input, and I want to verify that the user input is not duplicate. The user is making a list of chores, and so duplicate names won't work. When the user taps 'save', the unwind segue performs, and the data is added to an array.
Here's the problem: the array is on 'A', but the validation needs to happen on 'B' before 'A' gets called. How do I do that?
What I've tried:
I've tried using shouldPerformSegue in 'B', but the array comes back blank []. So that's no good. Here's the code from 'B':
override func shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool {
print("identifier is: ", (identifier))
print("sender is: ", (sender)!)
let newVC = Step3VC()
print(newVC.dailyJobs)
return false
}
So then I tried putting the validation into 'A' during the unwind segue...
#IBAction func unwindToStep3VC(sender: UIStoryboardSegue) {
let sourceVC = sender.source as! Step3AddJobVC
let updatedJob = sourceVC.job
// check for duplicate names
for name in dailyJobs {
print(name.name)
if name.name.lowercased() == (sourceVC.jobTextField.text?.lowercased()) { // check to see if lowercased text matches
print("error")
// call alert function from sourceVC
sourceVC.duplicateNameCheck()
return
}
}
if let selectedIndexPathSection = jobsTableView.indexPathForSelectedRow?.section { // if tableview cell was selected to begin with
// Update existing job
if selectedIndexPathSection == 0 {
let selectedIndexPathRow = jobsTableView.indexPathForSelectedRow
dailyJobs[(selectedIndexPathRow?.row)!] = updatedJob!
jobsTableView.reloadData()
} else if selectedIndexPathSection == 1 {
let selectedIndexPathRow = jobsTableView.indexPathForSelectedRow
weeklyJobs[(selectedIndexPathRow?.row)!] = updatedJob!
jobsTableView.reloadData()
}
} else {
// Add a new daily job in the daily jobs array
let newIndexPath = IndexPath(row: dailyJobs.count, section: 0)
dailyJobs.append(updatedJob!)
jobsTableView.insertRows(at: [newIndexPath], with: .automatic)
}
}
...but it gave the error:
popToViewController:transition: called on <ToDo_App.SetupNavController 0x7fcfd4072c00> while an existing transition or presentation is occurring; the navigation stack will not be updated.
If I pull out the 'if' validation code, the unwind segue works properly. The data is transferred and does the right thing. The problem is that if the user enters duplicate entries, I can't figure out how to stop them.
This is my code for checking if user input is duplicate:
// check for duplicate names
for name in dailyJobs {
print(name.name)
if name.name.lowercased() == (sourceVC.jobTextField.text?.lowercased()) { // check to see if lowercased text matches
print("error")
// call alert function from sourceVC
sourceVC.duplicateNameCheck()
return
}
}
What am I missing? Is there a better way to do this? How do I call the variables from 'A' while I'm in 'B' to perform my validation BEFORE the unwind segue is called / performed?

Answer 1

You are trying to validate the things in shouldPerformSegue which is the right place, the thing which you are doing wrong is recreating new object of Step3VC and trying to access dailyJobs which is never set with value.
let newVC = Step3VC()
print(newVC.dailyJobs)
What you have do is pass dailyJobs form VC A to VC B while presenting VC B and then check if the data is duplicate or not in shouldPerformSegue.
Your code have to look like:
class VCA: UIViewController {
var dailyJobs = getDailyJobsFromServer()
#IBAction segueToVCB(sender: UIButton) {
let sb = UIStoryboard(name: "Main", bundle: nil)
let vcB = sb.instantiateViewController(withIdentifier: "VCB") as! VCB
vcB.dailyJobs = dailyJobs
self.present(vcB, animated: true, completion: nil)
}
}
class VCB: UIViewController {
var dailyJobs: //DataType
override func shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool {
//Here you do comparision with dailyJobs
if dailyJobs == userInput {
}
return false
}
}