I'm wanting to make a subclass of UITableViewController that has some specific functions in it. That way when I make a TableViewController in the storyboard I can just subclass this new class I made.
But when I try to replace UITableViewController with my new class, I get errors about not having viewDidLoad() function or any of the other lifecycle functions.
Here is my subclass of UITableViewController:
class TutorialTVC: UITableViewController {
var tutorialTab: TutorialTab?
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
self.tutorialTab?.dropDownTab()
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
self.tutorialTab?.pullUpTab(0.2)
}
func createTutorialTab(segueNameOnOpen: String) {
self.tutorialTab = TutorialTab(sourceVC: self, putTabBelowView: nil, segueNameOnOpen: segueNameOnOpen)
}
}
As you can see, I tried adding in the override for viewDidLoad(), but even then is states this:
Method does not override any method from its superclass.
I thought that when you subclass something, all of it's functions are brought in as well... Or is there additional code I need to add to make this happen. I'm pretty new to subclassing like this.
My guess is you didn't import UIKit in this file. However you can create your class as subClass of UITableViewController right from the interface as below,
This will handle import of UIKit. Also it will add all the essential methods to start with TableViewController.
Related
The title basically asks my question for me. I have a number of view controllers which I'm loading in or dismissing as a user goes through the app. I'm having some asynchrony issues with the dismiss calls being called potentially too much. It's been a bit of a doozy going through the code base and finding what is being called where. I'd like to just print off whenever a new UIViewController hits the points in it's lifecycle functions viewWillAppear() or viewWillDisappear(). Is there a way for me to extent the UIViewController in such a way that all of its subclasses will naturally do this? Or would I have to go through each subclass to add in that code?
Thank you!
You could create a new UIViewController base class with the following:
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
print("\(type(of: self)) will appear")
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
print("\(type(of: self)) will disappear")
}
You'll have to inherit from this class on any view controller whos events you want to log
I've been looking at and trying all the solutions others have posted to this problem, but I'm still not getting it.
My use case is very simple. I have a viewController with a button, when that button is pressed I want to navigate to another tab and reload the data including an api call.
When using the button, I navigate to the tab fine, but viewDidAppear is not being called.
If on another tab, and navigate using the tab bar, viewDidAppear works fine. Also viewWillAppear is working, but I have to add a manual delay to the functions I want to call so it's not ideal.
So what do I need to do to navigate using self.tabBarController.selectedIndex = 0 and get the functionality of viewDidAppear?
Update: The viewWillAppear method I added gets called but I have to add a delay to my functions in order for them to work, and it's a bit clunky, not ideal. Not sure why viewDidAppear will not work :(
Here is a screenshot of the structure:
I appreciate any help on this one!
The "current" ViewController is my tab index 2:
import UIKit
class PostPreviewVC: UIViewController {
//Here I create a post object and post it to the timeline with the below button
#IBAction func postButtonPressed(_ sender: Any) {
//create the post via Firebase api
self.tabBarController?.selectedIndex = 0
}
}
In my destination viewController:
import UIKit
import Firebase
import SDWebImage
import AVFoundation
class HomeVC: UIViewController {
// MARK: - PROPERTIES
var posts = [Post]()
let refreshControl = UIRefreshControl()
//more properties...
#IBOutlet weak var tableView: UITableView!
override func viewDidLoad() {
super.viewDidLoad()
setupUI()
configureTableView()
reloadTimeline()
UserFirebase.timeline { (posts) in
self.posts = posts
self.tableView.reloadData()
}
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
print("viewDidAppear")
_ = self.view
setupUI()
configureTableView()
reloadTimeline()
UserFirebase.timeline { (posts) in
self.posts = posts
self.tableView.reloadData()
}
}
override func viewWillAppear(_ animated: Bool) {
super.viewDidAppear(animated)
print("viewWillAppear")
DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
self.reloadTimeline()
self.configureTableView()
}
}
//All the tableview code below here...
}
Added a custom class for my tab bar controller:
import UIKit
class TabBarController: UITabBarController, UITabBarControllerDelegate {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
print("viewDidAppear in tabBar custom Class called")
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
print("viewWillAppear in tabBar custom Class called")
}
}
When you are using UITabBarController, the method viewDidLoad will called only once when any UIViewController is loaded in memory. After that, when you are navigating the same UIViewController, then it will load from memory.
In order to overcome this problem, you must divide your code in viewDidLoad & viewDidAppear. So, in viewDidLoad, you only put that code which you want to intialize once throughout the app such as adding UIView's or other things, while in viewDidAppear / viewWillAppear, you can make API calls or some functions which fetches dynamic data.
Finally, when you are calling self.tabBarController.selectedIndex = 0, it will call viewDidLoad only once and viewDidAppear / viewWillAppear every time when you are navigating that UIViewController.
Hope this helps to understand like how UITabBarController works.
For UITabBarController viewDidLoad only gets called once. and your viewWillAppear and viewDidAppear get called multiple times. you can either check if your viewWillAppear gets called or not. because your view will appear gets called before your viewDidAppear it's just like going through the reverse engineering process.
You can also add viewDidAppear method into your UITabBarController custom class. and call its superclass method into it in that way I think it will solve your problem.
Note: In the case of UITabbarController, Always do your UI update task and API calling a task in either
viewWillAppear or viewDidAppear
I have an app with 6 UIViewControllers.
ANY viewcontroller features a function like this one:
#IBAction func onHelp(_ sender: UIBarButtonItem) {
DispatchQueue.main.async(execute: { () -> Void in
let helpVC = self.storyboard?.instantiateViewController(withIdentifier: "Help") as! HelpViewController
helpVC.starter = "MapHelp"
helpVC.helpSubtitle = "Map"
self.present(helpVC, animated: true, completion: nil)
})
}
Any IBAction in any viewcontroller presents the same HelpViewController but passing different parameters (starter and helpSubtitle).
Since I don't like to repeat code, first of all I thought this function should be converted to something more generic.
But: is there any way to create a generic IBAction, working for every viewcontroller?
Create a BaseViewController and add the generic method there.
class BaseViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
func genericMethod(starter: String, helpSubtitle: String){
let helpVC = self.storyboard?.instantiateViewController(withIdentifier: "Help") as! HelpViewController
helpVC.starter = starter
helpVC.helpSubtitle = helpSubtitle
self.present(helpVC, animated: true, completion: nil)
}
#IBAction func onHelp(_ sender: UIButton?) {
//You can use this method as generic IBaction if you want. It can be connected to buttons of all child View Controllers. But doing so will limit your param sending ability. On the plus side though, you won't have to define an IBAction everywhere and you can simply connect your child VC's button to Parent Class' IBAction.
}
}
Now inherit your ViewControllers from this class like:
import UIKit
class ViewController: BaseViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
#IBAction func btnTapped(_ sender: Any) {
genericMethod(starter: "View Controller", helpSubtitle: "I was triggered from VC1")
}
}
and
import UIKit
class SecondViewController: BaseViewController {
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
#IBAction func btnTapped(_ sender: Any) {
genericMethod(starter: "View Controller 2", helpSubtitle: "I was triggered from VC2")
}
}
That's it. Both your ViewControllers can call the parent method. If you still want to use the generic IBAction, you can do that too but I'd not recommend that course given that you want to pass params that can vary. If you wanted to do it though, it would look like this:
Bear in mind, the ViewController here has been inherited from the base ViewController which is why it can access the IBActions defined in the parent class. All you have to do is drag and connect.
How to stop animation of first view controller when second is started in swift programming. I have created a function which stops animation in first view controller. I want it to be called in second view controller.
In first View Controller
func stopAni(){
self.resultView.stopAnimating()
ButtonAudioPlayer.stop()
ButtonAudioPlayer1.stop()
ButtonAudioPlayer2.stop()
ButtonAudioPlayer3.stop()
ButtonAudioPlayer4.stop()
ButtonAudioPlayer5.stop()
ButtonAudioPlayer6.stop()
Not sure how to call this function in second view controller.
You can create a delegate something like:
protocol StopAnimationDelegate{
func stopAnimations()
}
Then, on your first view controller you're going to adopt this protocol:
class FirstViewController : UIViewController, StopAnimationDelegate{
//..... here code
func stopAnimations(){
//Stop your animations or call your method stopAni here.
}
//.... here more code
#IBAction func openSecondViewController(sender:UIButton){
self.performSegueWithIdentifier("segue_first_second",sender:nil)
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "segue_first_second"{
let secondViewController = segue.destinationViewController as! SecondViewController
secondViewController.delegate = self
}
}
}
On your second view controller, you can make something like:
class SecondViewController: UIViewController{
var delegate:StopAnimationDelegate?
#override func viewDidLoad(){
delegate?.stopAnimations()
}
}
Note: That's a way of how you can accomplish that, but all depends on what you need to do, for example you can simply stop the animations when you perform the segue (but again, that depends on what you want to do).
Another option, is using NSNotificationCenter to post a notification to Stop the animation, something like:
In First View Controller:
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
NSNotificationCenter.defaultCenter().addObserver(self, selector: "stopAnim", name: "kStopAnimations", object: nil)
}
//...Your stopAnim method
//... More Code
}
class SecondViewController : UIViewController{
override func viewDidLoad() {
NSNotificationCenter.defaultCenter().postNotificationName("kStopAnimations", object: nil)
}
}
I am trying to get to grips with delegates but the delegate I have set up seems to be nil and I am not sure why. I have a HomeViewController where the game is started from, then a UITableViewController where the player selects a row from a table. The row index is then used to pull data to be used in the game. The UITableViewController segues back to the HomeViewController where the game then starts. I thought I had put the correct protocol and delegate code in place but the delegate seems to be nil.
Any help much appreciated!
import UIKit
import Foundation
class HomeViewController: UIViewController, WordListsTableViewControllerDelegate {
override func viewDidLoad() {
super.viewDidLoad()
// sets up the game here
}
func wordListSelected(selectedWordList: Int) {
// passes the index path of the table to the AppWordList class to create the wordList for the game.
controller.wordList = AppWordList(wordListNumber: selectedWordList)
}
and in the TableViewController
import UIKit
protocol WordListsTableViewControllerDelegate {
func wordListSelected(selectedWordList: Int)
}
class WordListsTableViewController: UITableViewController {
var delegate: WordListsTableViewControllerDelegate?
override func viewDidLoad() {
super.viewDidLoad()
reloadData()
tableView.reloadData()
}
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
var selectedWordList = Int()
if (indexPath.section) == 2 {
selectedWordList = (indexPath.row) // Console shows the row is being selected ok.
delegate?.wordListSelected(selectedWordList) // IS NIL ???
// exit segue back to the HomeVC
performSegueWithIdentifier("startGameSegue", sender: nil)
}
}
You need to inform the HomeViewController class that has to be the delegate receiver for the class WordListsTableViewController, like this:
import UIKit
import Foundation
class HomeViewController: UIViewController, WordListsTableViewControllerDelegate
{
var wordListTableViewController = WordListTableViewController() // You forgot this
override func viewDidLoad() {
super.viewDidLoad()
wordListTableViewController.delegate = self // And this
// sets up the game here
}
func wordListSelected(selectedWordList: Int) {
// passes the index path of the table to the AppWordList class to create the wordList for the game.
controller.wordList = AppWordList(wordListNumber: selectedWordList)
}
You're missing a very important point about the Delegate Pattern, you need to keep a reference to the class that delegate its function and set it delegate in the class that handle the function. So let suppose you present the WordListsTableViewController by a segue from the HomeViewController like in the following example:
class HomeViewController: UIViewController, WordListsTableViewControllerDelegate {
// the reference to the class that delegate
var wordListTableViewController: WordListsTableViewController!
override func viewDidLoad() {
super.viewDidLoad()
// sets up the game here
}
func wordListSelected(selectedWordList: Int) {
// passes the index path of the table to the AppWordList class to create the wordList for the game.
controller.wordList = AppWordList(wordListNumber: selectedWordList)
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
// get the reference to the WordListsTableViewController
self.wordListTableViewController = segue.destinationViewController as! WordListsTableViewController
// set as it delegate
self.wordListTableViewController.delegate = self
}
}
And then you should be notified from the WordListsTableViewController, in the above example I assume the use of segues, but if you present the WordListsTableViewController you can use the same principle of keep a reference to the delegate class, like I show in the above example.
I do not apply any concept in code regarding the retain-cycles that can be happen in the use of delegates, but you can read more in my answer of this question about how to implement delegates correctly:
"fatal error: unexpectedly found nil while unwrapping an Optional value" while calling a protocol method
I strongly recommend you read more about the Delegate Pattern in this post:
How Delegation Works – A Swift Developer’s Guide
I hope this help you.
In your HomeViewController you have to set delegate to self:
override func viewDidLoad() {
super.viewDidLoad()
// get reference to your word lists table view controller
// if controller is your table view that should work
// controller.delegate = self
let wordLists = WordListsTableViewController....
// set up delegate
wordLists.delegate = self.
}