This is driving me crazy. The function updateTextView() is being called, verified by the print statements, but it is not setting the label in my view controller, and the print statements for the label are returning nil even though it has a default value set which is visible when the app is loaded. Whats more perplexing is that I set up a test button to call this function separately, and when I call it with test(), then the label updates properly.
class GoalDetailViewController: UIViewController, TextDelegate {
#IBAction func test(sender: AnyObject) {
updateTextView()
}
func updateTextView() {
print(goalSummaryTextBox?.text)
print("delegate called")
self.goalSummaryTextBox?.text = GoalsData.summaryText
print(goalSummaryTextBox?.text)
}
#IBOutlet weak var goalTitle: UILabel?
#IBOutlet weak var goalCreationDate: UILabel?
#IBOutlet weak var goalSummaryTextBox: UITextView?
override func viewDidLoad() {
super.viewDidLoad()
goalSummaryTextBox?.text = GoalsData.summaryText
}
}
updateTextView() is being called through a delegate method after I pop a different view controller, as can be seen below:
class TextEditViewController: UIViewController {
var textDelegate: TextDelegate?
#IBOutlet weak var textView: UITextView?
func configureView() {
navigationItem.title = "Edit Description"
navigationItem.setRightBarButtonItem((UIBarButtonItem(barButtonSystemItem: .Done, target: self, action: "segue")), animated: true)
}
func segue() {
textDelegate = GoalDetailViewController()
if let text = textView?.text {
GoalsData.summaryText = text
}
textDelegate?.updateTextView()
self.navigationController?.popViewControllerAnimated(true)
}
}
The line causing the issue is in the TextEditViewController below:
textDelegate = GoalDetailViewController()
What this line does is creates a new instance of GoalDetailViewController, and sets it as the delegate to the TextEditViewController. But, what you want is the original instance of GoalDetailViewController to be the delegate. This is why you were seeing the logs when popping TextEditViewController, since it was executing the other instance (which wasn't part of the view hierarchy). It also explains why all your IBOutlets are nil when stepping through updateTextView() on the delegate call, and that the button you added updates the text properly.
The solution is to make the delegate connection in the prepareForSegue method:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if let destination = segue.destinationViewController as? TextEditViewController {
destination.textDelegate = self
}
}
Add the above code to your GoalDetailViewController.
EDIT:
The below code will ensure that this problem does not happen in the future. Change the delegate's definition to:
weak var textDelegate: TextDelegate?
and change your protocol to:
protocol TextDelegate: class {
func updateTextView()
}
Related
Via a method or closure, perhaps?
I created a subclass view controller of my superclass/parent view controller and placed labels with placeholder text in that subclass view controller.
I want to set the labels' values to blank strings from the superclass/parent view controller, or, specifically, from an IBAction function that causes the subclass view controller to appear.
Here is the code, first from the parent class, then from the subclass...
'''
class ViewController: UIViewController {
#IBAction func leavingView(){
self.EntryViewController.entryDateLabel.text = ""
self.EntryViewController.entryLabel.text = ""
self.dismiss(animated: true, completion: nil)
}
'''
then from the subclass...
'''
class EntryViewController: ViewController {
#IBOutlet var entryDateLabel: UILabel!
#IBOutlet var entryLabel: UILabel!
}
'''
I have come up with 2 solutions to this problem, without having the parent view controller know about its subclass.
In the first example the parent sets properties on itself that the child listens to (via the didSet method, it then updates its view accordingly. However, this isn't ideal because the entryDate and entry string fields are useless on their own, almost redundant in the parent.
class ParentViewController: UIViewController {
var entryDate: String?
var entry: String?
#IBAction func leavingView(){
self.entryDate = ""
self.entry = ""
self.dismiss(animated: true, completion: nil)
}
}
class ChildViewController: ParentViewController {
#IBOutlet var entryDateLabel: UILabel!
#IBOutlet var entryLabel: UILabel!
override var entryDate: String? {
didSet {
guard isViewLoaded else {
return
}
entryDateLabel.text = entryDate
}
}
override var entry: String? {
didSet {
guard isViewLoaded else {
return
}
entryLabel.text = entry
}
}
}
In my opinion, the second solution is clearer and keeps implementation details more separate because you're using instructions or events to notify the child view controllers.
class ParentViewController: UIViewController {
#IBAction func leavingView(){
self.dismiss(animated: true, completion: didLeaveView)
}
func didLeaveView() { }
}
class ChildViewController: ParentViewController {
#IBOutlet var entryDateLabel: UILabel!
#IBOutlet var entryLabel: UILabel!
override func didLeaveView() {
entryDateLabel.text = ""
entryLabel.text = ""
}
}
Since your requirement is not that much clear I have created a demo for you and into that demo I have added child ContainerViewController into parent ViewController and from that parent view controller you can change UILabel text when you click on UIButton of parent ViewController and code will be for ViewController
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func btnFromParentViewTapped(_ sender: Any) {
//Here get the child of your parent view controller
if let containerView = self.children[0] as? ContainerViewController {
containerView.lblContainer.text = ""
}
}
}
and ContainerViewController code will be:
class ContainerViewController: UIViewController {
#IBOutlet weak var lblContainer: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
}
Don't need to add much here because you are accessing it from parent view.
And your result will be:
As you can see when I click on button which title says Change Container label text the label text from ContainerViewController set to empty string.
For more info check THIS demo project.
This is the error Xcode outputs
Unexpectedly found nil while unwrapping an Optional value
I have a viewcontroller that has a tableview and a few buttons; the buttons allow me to insert or remove data. It seems that when I click on Add (which brings up a new viewcontroller via segue as a sheet) the app crashes with the error above. Clicking on remove doesn't have this affect. So it has to do with something regarding the new viewcontroller as a guess. The console doesn't go further into the error other than printing out (lldb)
Here's my code
override func viewDidLoad() {
super.viewDidLoad()
alarmTableView.dataSource = self //error occurs here
alarmTableView.delegate = self //if i remove the above line if will occur here too.
}
My Viewcontroller which the above viewDidLoad func is embedded lists the protocols I need
class ViewController: NSViewController, NSTableViewDelegate, NSTableViewDataSource {
#IBOutlet weak var addAlarm: NSButton!
#IBOutlet weak var resetDataButton: NSButton!
#IBOutlet var alarmArrayController: NSArrayController!
#IBOutlet weak var alarmTableView: NSTableView!
#IBOutlet weak var deleteAll: NSButton!
#objc let moc: NSManagedObjectContext
required init?(coder: NSCoder) {
self.moc = CoreDataHandler.getContext()
super.init(coder: coder)
}
override func prepare(for segue: NSStoryboardSegue, sender: Any?) {
let destinationController = segue.destinationController as! AddAlarmViewController
//pass data to next controller here
}
#IBAction func deleteAllAction(_ sender: Any) {
if (alarmTableView.selectedRow >= 0) {
if (CoreDataHandler.deleteAllObjectsInEntity(entityName: "Alarm")) {
//remove from nsarray controller
for object in alarmArrayController.arrangedObjects as! [Alarm] {
print(object)
alarmArrayController.removeObject(object)
}
alarmTableView.reloadData()
}
}
else {
printInfo(str: "There are no alarms to delete")
}
}
/* Response to the remove alarm button - It removes a selected alarm object from the table */
#IBAction func resetDataAction(_ sender: Any) {
if (alarmTableView.selectedRow >= 0) {
let selectedAlarm = self.alarmArrayController.selectedObjects.first as! Alarm
alarmArrayController.remove(atArrangedObjectIndex: alarmTableView.selectedRow)
CoreDataHandler.deleteObjectInEntity(entityName: "Alarm", obj: selectedAlarm)
alarmTableView.reloadData()
}
else {
//will need a warning or play a sound.
printInfo(str: "Please select an alarm")
}
}
override func viewDidLoad() {
super.viewDidLoad()
printInfo(str: "viewdidload")
print(alarmTableView)
if (alarmTableView != nil) {
printInfo(str: "AlarmTableView Is initialised")
alarmTableView.dataSource = self
alarmTableView.delegate = self
}
else {
printInfo(str: "AlarmTableView is not initialised")
}
}
override var representedObject: Any? {
didSet {
// Update the view, if already loaded.
}
}
func printInfo(str: String) {
print("ViewController: \(str)")
}
func tableView(_ tableView: NSTableView, heightOfRow row: Int) -> CGFloat {
return 100.0
}
}
class AddAlarmViewController: ViewController {
#IBOutlet weak var closeButton: NSButton!
override func viewDidLoad() {
super.viewDidLoad()
// Do view setup here.
printClassInfo(str: "viewDidLoad")
CoreDataHandler.saveTestData()
}
#IBAction func closeButtonAction(_ sender: Any) {
self.dismissViewController(self)
}
func printClassInfo(str: String) {
print("AddAlarmViewController \(str)")
}
}
If I remove the lines where the error occurs the app run fine. But I want to override the delegate and datasource and use the functions to further customise the table. I'm also using Cocoa Bindings.
Why am I getting this error?
Update
I haven't solved it yet, but i placed a couple of print statements in my viewDidLoad function. It seems that when the app is first loaded, the table view is initialised. But after when I clicked on the Add button, the table view is then set to nil for some odd reason, as if another table view has been initialised. However the data is still visible
Problem:
class AddAlarmViewController: ViewController {
//...
override func viewDidLoad() {
super.viewDidLoad()
//...
}
}
Your AddAlarmViewController is a subclass of ViewController instead of NSViewController.
In AddAlarmViewController's viewDidLoad you call super.viewDidLoad() which basically calls ViewController's viewDidLoad.
But... in this case ViewController is a new instance as the super class of AddAlarmViewController and none of it's properties are initialized.
Whatever it be, it's probably not what you want.
Solution:
class AddAlarmViewController: NSViewController {
//... rest as it is
}
I am doing a Mac application, and I have a problem appending text to a NSScrollView when I call a function from a different class.
I have this function on my ViewController class:
import Cocoa
class PopoverVC1: NSViewController {
let popover1 = NSPopover()
class func loadView() ->PopoverVC1 {
let vc = NSStoryboard(name: NSStoryboard.Name(rawValue: "Main"),
bundle: nil).instantiateController(withIdentifier:
NSStoryboard.SceneIdentifier(rawValue: "Popover1")) as! PopoverVC1
vc.popover1.contentViewController = vc
return vc
}
override func viewDidLoad() {
super.viewDidLoad()
popover1.behavior = .transient
popover1.contentViewController = self
}
func showPopover (view: NSView){
popover1.show(relativeTo: view.bounds, of: view, preferredEdge: .maxY)
}
#IBOutlet weak var radioOption1: NSButton!
#IBOutlet weak var radioOption2: NSButton!
#IBOutlet weak var radioOption3: NSButton!
#IBAction func clickOption(_ sender: NSButton) {
switch sender {
case radioOption1: popover1.performClose(sender)
case radioOption2: let vc = ViewController()
vc.myPrint(string: "This is a test")
default: print ("hello")
}
}
}
Than I have a PopoverVC1 class, which is a class to a popover I am using:
import Cocoa
class ViewController: NSViewController {
#IBOutlet weak var oneYes: NSButton!
#IBOutlet weak var oneNo: NSButton!
#IBOutlet weak var notesArea: NSScrollView!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override var representedObject: Any? {
didSet {
// Update the view, if already loaded
}
}
func myPrint (string: String){
let mystring = string
let myNotes = notesArea.documentView as? NSTextView
let text = myNotes?.textStorage!
let attr = NSAttributedString(string: mystring)
text?.append(attr)
}
let popover1 = NSPopover()
#IBAction func oneClicked(_ sender: NSButton) {
switch sender {
case oneYes: let vc = PopoverVC1.loadView()
vc.showPopover(view: sender)
case oneNo:
let myNotes = notesArea.documentView as? NSTextView
let text = myNotes?.textStorage!
let attr = NSAttributedString(string: "test")
text?.append(attr)
default: print ("")
}
}
}
However, I got an error when I press the radio button "oneNo" that should call the function "myPrint" and pass the argument.
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an Optional value
I did some tests and when I call this same function "myPrint" from within the ViewCotroller class it works fine.
Any ideas?
Your issue is in clickOption when you are calling:
let vc = ViewController()
vc.myPrint(string: "This is a test")
When you call this method from code and the ViewController's UIViews are set up in a storyboard, the connection from the storyboard is not made. That is why the notesArea is nil when you call the function myPrint. In this case you are creating a new copy of ViewController and it will not be the same one that created the popover.
There are a few ways you can solve the problem that you are trying to accomplish. One of them is known as a delegate. This is a way for you to to call the ViewController's methods like your popover inherited them. You can check out a tutorial here. The idea is that we want to have a reference to the ViewController in your popover so that you can call the functions in the protocol. Then the ViewController that conforms to the protocol will be responsible for handling the method call.
So let's create a protocol called PrintableDelegate and have your ViewController class conform to it. Then in your popover, you will be able to have a reference to the ViewController as a weak var called delegate (you can use what ever name you want but delegate is standard). Then we can call the methods described in the protocol PrintableDelegate, by simply writing delegate?.myPrint(string: "Test"). I have removed some of your irrelevant code from my example.
protocol PrintableDelegate {
func myPrint(string: String)
}
class ViewController : UIViewController, PrintableDelegate {
func myPrint (string: String){
let mystring = string
let myNotes = notesArea.documentView as? NSTextView
let text = myNotes?.textStorage!
let attr = NSAttributedString(string: mystring)
text?.append(attr)
}
#IBAction func oneClicked(_ sender: NSButton) {
let vc = PopoverVC1.loadView()
// Set the delegate of the popover to this ViewController
vc.delegate = self
vc.showPopover(view: sender)
}
}
class PopoverVC1: NSViewController {
// Delegates should be weak to avoid a retain cycle
weak var delegate: PrintableDelegate?
#IBAction func clickOption(_ sender: NSButton) {
// Use the delegate that was set by the ViewController
// Note that it is optional so if it was not set, then this will do nothing
delegate?.myPrint(string: "This is a test")
}
}
I have a view controller embedded in another VC.
I would like to get the value of a variable from the main VC inside the embedded one. Specifically, I would like to change the text of label2 based on the value of label1.
I tried with "prepareForSegue", but it seems it's not triggered for embedded view controllers. I tried to isolate the problem in a test project:
Code for main VC:
class MyViewController: UIViewController {
#IBOutlet weak var label1: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
label1.text = "Hello"
}
}
Code for embedded VC:
class EmbeddedVC: UIViewController {
#IBOutlet weak var label2: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
}
Thanks for your help :)
A way to achiŠµve this is to get the child view controller instance in the parent's viewDidLoad. It appears that the parent's viewDidLoad: gets called after the child's viewDidLoad:, which means the label is already created in the child's view.
override func viewDidLoad() {
super.viewDidLoad()
if let childVC = self.childViewControllers.first as? ChildVC {
childVC.someLabel.text = "I'm here. Aye-aye."
}
}
First of all you can't set directly EmbeddedVC's lable2.text In prepareForSegue
because call sequence following below
MainVC's prepareForSeque this time EmbeddedVC's label2 is nil
EmbeddedVC's viewDidLoad called then label2 loaded
MainVC's viewDidLoad called then label1 loaded
so if you assign MainVC's label1.text to EmbeddedVC's label2.text in prepareForSeque
both label1 and label2 are nil so did not work
There are two way to solve this question
First Solution
MainViewController has EmbeddedVC and when MainVC's viewDidLoad called, assign label1.text to embeddedVC.label2.text
class MyViewController: UIViewController {
#IBOutlet weak var label1: UILabel!
var embeddedVC: EmbeddedViewController? = nil
override func viewDidLoad() {
super.viewDidLoad()
label1.text = "Hello"
embeddedVC?.label2.text = label1.text
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let embeddedVC = segue.destination as? EmbeddedViewController {
self.embeddedVC = embeddedVC
}
}
}
class EmbeddedViewController: UIViewController {
#IBOutlet weak var label2: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
}
Second Solution, use protocol and get MainVC's label text when viewWillAppear or viewDidAppear (later viewDidLoad called)
protocol EmbeddedVCDelegate: class {
func labelText() -> String?
}
class MyViewController: UIViewController, EmbeddedVCDelegate {
#IBOutlet weak var label1: UILabel!
// MARK: EmbeddedVCDelegate
func labelText() -> String? {
return label1.text
}
override func viewDidLoad() {
super.viewDidLoad()
label1.text = "Hello"
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let embeddedVC = segue.destination as? EmbeddedViewController {
embeddedVC.delegate = self
}
}
}
class EmbeddedViewController: UIViewController {
#IBOutlet weak var label2: UILabel!
weak var delegate: EmbeddedVCDelegate? = nil
override func viewDidLoad() {
super.viewDidLoad()
}
override viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
label2.text = delegate?.labelText()
}
}
You should try to use prepareForSegue like this:
if segue.identifier == "identifier" {
guard let destinationViewController = segue.destination as? VC2 else { return }
destinationViewController.label2.text = mytext
}
Where the segue identifier you assign in storyboard
I am beginner in swift and working on one project where I am using collectionView. From collectionView, I want to transfer some values to details view but I am getting the above mentioned error. Values are not nil but somehow, it is giving this error while performing segue. Anybody help me, I am badly stuck here.
//In my CollectionView Controller.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if(segue.identifier == "DetailsView")
{
if let vc:DetailsViewController = segue.destinationViewController as? DetailsViewController
{
vc.details.text = self.description
vc.line.text = self.subText
vc.startTime.text = self.formatted_time
}
}
}
//DetailsViewController
import UIKit
class DetailsViewController: UIViewController {
#IBOutlet var startTime: UILabel!
#IBOutlet var line: UILabel!
#IBOutlet var details: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}
This basically means your IBOutlets are not yet initialised.
You should set strings and then in the viewDidLoad set you labels.
So to sum up:
Add string properties in your DetailsViewController
Set these string properties in your preparForsegue function
in the viewDidLoad of your DetailsViewController, set your labels
Your code should look like something like this :
//In my CollectionView Controller.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if(segue.identifier == "DetailsView")
{
if let vc:DetailsViewController = segue.destinationViewController as? DetailsViewController
{
vc.detailsString = self.description
vc.lineString = self.subText
vc.startTimeString = self.formatted_time
}
}
}
//DetailsViewController
import UIKit
class DetailsViewController: UIViewController {
#IBOutlet var startTime: UILabel!
#IBOutlet var line: UILabel!
#IBOutlet var details: UILabel!
var startTimeString: String?
var lineString: String?
var detailsString: String?
override func viewDidLoad() {
super.viewDidLoad()
startTime.text = tmpStartTimeString
line.text = tmpLineString
details.text = tmpDetailsString
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
}
Double check my code, I've wrote it very quickly ;)
The IBOutlets in a destination view controller aren't set until some time after prepareForSegue finishes
In DetailsViewController, add three instance variables:
var startTime: String?
var line: String?
var details: String?
Then in prepareForSegue, set those three values:
vc.details = self.description
vc.line = self.subText
vc.startTime = self.formatted_time
Then in viewDidLoad of DetailsViewController
detailsLabel.text = self.details
lineLabel.text = self.line
startTimeLabel.text = self.startTime
As the two answer above are point out when you create an instance of a UIViewController like for example in the prepareForSegue when you call segue.destinationViewController as? DetailsViewController this not mean that the #IBOutlet's are injected or initialized yet. The #IBOutlet's are initialized when the view is fully loaded, so you can do two of the following options:
Create variables in your UIViewController in which you can save the values after the init of the UIViewController in the prepareForSegue and then in the viewDidLoad() of the another UIViewController you set the values for the #IBOutlet's.
Another option is call the view (e.g let _ = vc.view) property when you create the instance of the UIViewController, in this way you can force the view to load load fully and you can set your #IBOutlet's from the prepareForSegue.
I hope this help you.