Up to date Xcode/Swift/iOS.
I have a Master VC (called StartVC) that contains a Child VC (called TopBarVC) via and embedded segue. The Child VC contains a button, that, when pressed, modally segues to a 3rd VC (called CategoryPickerOverlayVC) (the view in this VC serves as a dropdown box for picking a category).
#IBAction func CategoryFilterButtonPressed(_ sender: Any) {
performSegue(withIdentifier: "toCategoryPickerOverlay", sender: self)
}
When an option is selected from the dropdown box, which itself is composed of three buttons, the title of the selected button should be used to replace the title text of the button in the Child VC.
In the Master VC, I use prepareforsegue to store a reference to the Child VC in a variable - "topBarReference" - at the moment when the embed segue takes place.
var topBarReference: TopBarVC?
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "TopBarPane"{
topBarReference = segue.destination as? TopBarVC
}
}
Then, in the 3rd VC, when I click on one of the button options in the dropdown box, the button title is sent via a prepareforsegue to update the button in the Child VC (via "topBarReference").
if segue.identifier == "unwindToStartVC"{
let vc = segue.destination as! StartVC
vc.topBarReference?.filterButtonText = ((sender as! UIButton).titleLabel?.text)!
}
The 3rd VC then unwind segues back to the Master VC. I should add that when the button in the Child VC is changed, a variable (filterButtonText) in Child VC is first set with the title text and then this variable is then used to set the button title text via the viewDidAppear method of Child VC.
When using the debugger, I also note that viewDidAppear in the Master VC does not seem to execute after unwinding (I placed a diagnostic print-to-console in viewDidAppear and nothing prints after the unwind segue). I realise this would explain the button not getting updated but I've got no idea why viewDidAppear does not run.
I have also tried using a delegate protocol and instantiateViewController(withString:) to no avail. All of the methods produce the same result, which is that the button in the Child VC does not get updated. No errors are shown. Everything else happens as expected.
Any ideas as to what I am doing wrong?
Do you mean something like this?
If so, the solution I used was very simple: the third VC uses prepareForSegue to set a property of the embedded VC, and the embedded VC picks up that property in the unwind method.
In my implementation, the three view controllers are called ViewController, ChildViewController, and ThirdViewController. This is the entire code (everything else is configured in the storyboard):
class ChildViewController: UIViewController {
#IBOutlet weak var theButton: UIButton!
var buttonTitle : String?
#IBAction func unwind(_:UIStoryboardSegue) {
self.theButton.setTitle(self.buttonTitle, for: .normal)
}
}
class ThirdViewController: UIViewController {
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
(segue.destination as! ChildViewController).buttonTitle = (sender as! UIButton).currentTitle
}
}
Ok, so I have found that my original code works fine bar one line in the prepareforsegue of the Child VC. If I change that prepareforsegue from:
if segue.identifier == "unwindToStartVC"{
let vc = segue.destination as! StartVC
vc.topBarReference?.CategoryFilterButton.titleLabel?.text = ((sender as! UIButton).titleLabel?.text)!
}
to this:
if segue.identifier == "unwindToStartVC"{
let vc = segue.destination as! StartVC
vc.topBarReference?.CategoryFilterButton.setTitle((sender as! UIButton).titleLabel?.text, for: .normal)
}
it works just fine. The use of the .setTitle method seems to make a difference although I am not sure why.
Thanks to Matt for giving me the idea to change it to that. Matt's method did work when i tried it, although, as I am unwinding to the Master VC and not the Child VC, I had to edit the code accordingly, in terms of where I placed it.
As my little "discovery" equates to the smallest change to the original code, I'll mark this as the answer.
Thanks to all for taking the time to respond!
Related
I have a view controller with a container view that has a tab bar controller embedded in it. Im using this to display 3 different view controllers based on what is pressed from a segmented control in the main vc. I have been following this solution: https://stackoverflow.com/a/38283669/11536234
My problem is that when I change the segmented control index (by pressing a different segment) I can't figure out how to "reach" the prepare function.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
print("prepare reached")
//super.prepare(for: segue, sender: sender)
//switch(segue.identifier ?? "") {
//case "TabBar":
guard let TabController = segue.destination as? UITabBarController else {
fatalError("Unexpected destination: \(segue.destination)")
}
TabController.selectedIndex = toggle.selectedSegmentIndex
//default:
//fatalError("Unexpected Segue Identifier; \(segue.identifier)")
//}
}
#IBAction func toggleAction(_ sender: UISegmentedControl) {
print("toggle is now at index: ", toggle.selectedSegmentIndex)
//performSegue(withIdentifier: "TabBar", sender: sender)
//container.bringSubview(toFront: views[sender.selectedSegmentIndex])
}
So far i have tried placing a performsegue function in an action function linked to the segmented control. This doesn't work, however, because it essentially adds another embedded tab bar programmatically or calls the embed segue again and I receive this error statement: "There are unexpected subviews in the container view. Perhaps the embed segue has already fired once or a subview was added programmatically?"
*The commented lines of code are there to show what I've tried that hasn't worked vs where I'm at.
When you embed a view controller to a container view from another view controller(MainVC), the segue is performed only once when MainVC loads. To pass values to the embedded UIViewController/UITabBarController, you need to get the child view controller and send the data
class MainVC: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func segmentControlAction(_ sender: UISegmentedControl) {
if let tabBarVC = self.children.first(where: { $0 is UITabBarController }) as? UITabBarController {
tabBarVC.selectedIndex = sender.selectedSegmentIndex
}
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
//called before mainvc viewDidLoad
let destinationVC = segue.destination as? UITabBarController
destinationVC?.selectedIndex = 1
}
}
You can't do what you are trying to do.
With embed segues the segue fires when the host view controller is first loads. That invokes your prepare(for:sender) method, once and only once, before the embedded view controller's views are loaded. It doesn't get called again.
What you need to do is to save a pointer to your child view controller in an instance variable. Define a protocol that the parent uses to talk to the child, and then use that protocol to send a message to the child when the user selects a different segment in your segmented control.
Then the child (presumably the tab bar controller) can switch selected tabs in response to the message you define.
I have a storyboard with two main view controllers (ViewController / SecondViewController) and a container with an embedSegue that displays the EmbeddedViewController view.
Desired Result
I would like to pass the 5 from ViewController to EmbeddedViewController using prepareForSegue (I don't see a need for delegation here, since the data is only going 1 way, and that's TO the EmbeddedViewController.) Once "Segue" button is pressed, the second view controller appears with the yellow VC embedded with 5 in it.
Note - SecondViewController has no user interaction in displaying EmbeddedViewController. It just shows up automatically.
Problem
I can't get a reference to EmbeddedViewController from the mainSegue prepareForSegue. Nor can I access any child View Controllers from SecondViewController. Thought I could access properties of EmbeddedViewController if I access the children VC's of SecondViewController. See code below.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "mainSegue" {
let secondVCSegue = segue.destinationViewController as! SecondViewController
print("array -- \(secondVCSegue.childViewControllers)")
// Array prints nothing. Just a blank [] :(
}
}
Any tips are appreciated thanks.
I am using for the first time the Unwind Segue approach. I have multiple view controllers as can be seen in the picture below (a few of them shown of course). In the Edit Profile I have a Done button. Once clicked I trigger an IBAction that triggers an unwind segue.
Here is the code for the Done button in the nav bar:
#IBAction func unwindToMainViews(sender: UIStoryboardSegue) {
//let sourceViewController = sender.sourceViewController
self.performSegueWithIdentifier("unwindToMainSegue", sender: self)
}
and in the
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject!)
I am doing the following to pass data from Edit Profile back to Home View
if (segue.identifier == "unwindToMainSegue") {
// pass data to next view
let tabCtrl = segue.destinationViewController as! UITabBarController
let destinationVC = tabCtrl.viewControllers![0] as! HomeViewController
destinationVC.userObject = self.userObject;
}
When segue identifier is matched and code is executed (to transfer userObject from this controller to another), it triggers the error:
Could not cast value of type 'app.EditProfileViewController' (0x100b99d80) to 'UITabBarController' (0x104a1d030).
How can this error be fixed? I am surprised since i am casting to UITabBarController so thought it should work.
You don't return to the UITabBarController in an unwind segue. You return to the ViewController that triggered the original segue, or one if its ancestors.
As #jlehr stated in the comments:
Unwind segues don't return to anything; they dismiss any pushed and
presented view controllers between the source and destination view
controller. The destination is wherever the implementation of the
unwind method is found, regardless of how the source view controller
was presented.
To unwind to the viewController that triggered the original segue, you need to implement the #IBAction func returnToHere(segue: UIStoryboardSegue) function in the viewController you want to return to.
Then when you set up your Done button by dragging to the Exit icon, you select returnToHere from the pop-up.
To pass data back to the sourceViewController, give your unwind segue an identifier such as "unwindToSource", then override prepareForSegue in the viewController you are returning from:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "unwindToSource" {
let dvc = segue.destinationViewController as! SourceViewController
dvc.userObject = self.userObject
}
}
I have an app setup to have a Master root viewController with a Navigation bar that has a "Settings button". When the user taps the settings button, it brings up a 'settingsTableViewController' that is not dynamic, but rather static so i can format the tableviews with settings like style.
in this settings view, i have a UITextField that takes a Person's name.
When the user clicks "Done" in the navigation bar, i want to pass that name back to the Master Root ViewController so i can use it in the title to display the Person's name. (I want to pass the name upon dismissing the view)
I have tried to use segue's but no luck. Here is a bit of what i tried.
SettingsViewController (pop's over the MasterVC)
class SettingsTableViewController: UITableViewController {
#IBOutlet weak var nameTextfield: UITextField!
#IBAction func done(sender: AnyObject) {
self.dismissViewControllerAnimated(true, completion: nil)
}
override viewDidLoad(){
self.title = "Settings"
}
// MARK: - Navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
// Trying to pass what was typed in the textfield to the Root ViewController and store this name in a variable of type String called 'name'
if segue.identifier == "masterView"{
let masterViewController = segue.destinationViewController as! MasterTableViewController
masterViewController.name = nameTextField.text
print("Segue was used")
}
}
}
MasterTableViewController.swift
class MasterTableViewController: UITableViewController {
var name: String!
// I am trying to then display the name entered in the pop-over view in this root view controller's title
override viewDidLoad(){
self.title = name!
}
}
My question is, what did i do wrong? I have tried to use delegation but i get nil and the data doesn't seem to get passed either way so any leads will greatly help. Thanks
There is a different kind of segue called Unwind Segue to do that. It doesn't create a new mvc and its used to pass data back to the vc that presented the current one. here is how to do it
First, go to your storyboard and control drag from settingVc to the exit button on top of it (to itself). it will give you 'Selection Segue' and choose IBAction goBack. This means any vc that presented the current one will get to prepare if they implement this method. In other words, you're putting out a protocol and the presenter vc will conform by implementing goBack IBAction. here is how to implement that. In your Mater vc
//You must have this function before you do the segue in storyboard
#IBAction func goBack(segue: UIStoryboardSegue){
/* this is optional
if let stv = segue.sourceViewController as? SettingsTableViewController{
self.name = stv.nameTextfield?.text
}
*/
}
In your setting vc (current vc)
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
//make sure you set the id of your segue to "Your Go back Unwind segue". ofc u can name it whatever
if segue.identifier == "Your Go back Unwind segue"{
if let mtvc = segue.destinationViewController as? MasterTableViewController{
mtvc.name = nameTextField.text
print("Segue was used")
}
}
}
and done method should be something like this
#IBAction func doneEditing(sender: UIButton) {
presentingViewController?.dismissViewControllerAnimated(true, completion: nil)
}
I've been trying to pass data to another View Controller. But as I have two Bar Buttons that lead to two different View Controllers I have to set a condition. But when I try to pass the data it won't work. Here's the code I've been using:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if (segue.identifier == "ViewController") {
let destViewController = segue.destinationViewController as! ViewController
destViewController.chips = chips
destViewController.blind = blind
}
}
I have my destination Storyboard id to ViewController but when ViewController view opens the data isn't passed through.
EDIT:
In both View Controllers chips and blind are declared as:
var chips = 0
var blind = 0
Before I added a back button the data was passed correctly. But then the application crashed every time I clicked "Back" so I decided to add a condition which doesn't seem to work.
I'm very new to Xcode/Swift, but I believe the string in your if (segue.identifier == "ViewController") is the problem. Instead of "ViewController" you need to use the identifier of your segue. Select your segue in Main.storyboard, click on the Attributes Inspector and give it a name in the Identifier field. That's the string you want to use.