assuming I have a viewcontroller (vcA) that pushes QRCodeScannerViewcontroller (vcB). When (vcB) scanned something, It will push ResultviewController (vcC).
-Those 3 views is connected to a UInavigation controller
-the user clicks on the back button on (vcC)
my question is:
1)how can I know if (vcB) is visible without changing code on (vcB)? (vcB) is a pod
2)where will I put this code? I can only access (vcA)
i tried adding this code on (vcA) but nothing happened
override func viewDidDisappear(_ animated: Bool) {
if (vcB.isViewLoaded && (vcB.view.window != nil)){
print("vcb did appear!")
}
}
To know if an instance of cvB's class exists in the navigation stack, you could use this piece of code:
let result = self.navigationController?.viewControllers.filter({
if let vcB = $0 as? UIViewController { // Replace UIViewController with your class, for example ViewControllerB
return true
}
return false
})
if result.isEmpty {
print("An instance of vcB's class hasn't been pused before")
} else {
print("An instance of vcB's class has been pused before")
}
Related
When we perform a segue, it is easy to get the destination view controller so we can pass data to it using the prepare(for:) method.
I'd like to know the correct way to do this when the back button of a navigation controller is pressed.
I've managed to piece together something that works, but it feels wrong to be using my knowledge of the hierarchy of the view controllers within the navigation controller rather than getting the destination dynamically. Maybe i'm overthinking it?
override func willMove(toParent parent: UIViewController?) {
super.willMove(toParent: parent)
// This method is called more than once - parent is only nil when back button is pressed
if (parent == nil) {
guard let destination = self.navigationController?.viewControllers.first as? MyTableViewController else {
return
}
print("destination is \(destination)")
// set delegate of my networking class to destination here
// call async method on networking class to retrieve updated data for my table view
}
}
As a general rule, trying to do that makes for too tight of a coupling. The VC you are navigating away from shouldn't need to know about where it's headed.
Probably better to implement your networking class methods in viewWillAppear or viewDidAppear inside your MyTableViewController class.
However, you could give this a try:
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
// make sure we're in a navigation controller
guard let navC = navigationController else { return }
if navC.viewControllers.firstIndex(of: self) != nil {
// we're still in the nav stack, so we've either
// pushed to another VC, or presented a full-screen VC
// (or maybe something else)
return
}
// we've been removed from the nav stack
// so user tapped Back button
print("back button tapped")
// see if we're navigating back to an instance of MyTableViewController
guard let destVC = navC.viewControllers.last as? MyTableViewController else {
return
}
// do something with destVC...
print("on our way to", destVC)
}
Note: I just did this as an example... it would need plenty of testing and possibly additional case handling.
Is there any equivalent in Swift to RACObserve(self, presentingViewController)?
Or any other why to imitate this behaviour?
My issue is that I want to be notified whenever a view controller is "hidden" by another view controller. In objc what I'd do is to check if self.presentingViewController is nil.
Note that in this scenario there's no knowledge of which view controller is presented, so it's impossible to notify from within its viewDidAppear/viewDidDisappear.
As I understand your question: you need to to know which view controller is presented now and you need notification inviewDidAppear/viewDidDisappear.
So we can get this in several way.
The simple way is:
Get information of which is the top ViewController right now.
2.Call this method in your viewDidAppear/viewDidDisappear
Like this :
Get Which is The Top ViewController
func getTopViewController() -> UIViewController? {
if var topVC = UIApplication.shared.keyWindow?.rootViewController {
while let presentedViewController = topVC.presentedViewController {
topVC = presentedViewController
return topVC
}
return topVC
}
return nil
}
Call in viewDidAppear:
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(true)
if let top = getTopViewController() {
print("topView Controller name \(top.title)")
top.view.backgroundColor = .red
}
}
Hope it will help you !
I have NSObject class listening for a specific event from my server.
When this specific event happens, I would like to update the badge value of an existing tabBar item from my UITabBarController called TabBarController.
How can I access it from the NSObject class?
Below is the NSOBject class listening for the event.
The function connectedToSocketIo() is launched when the application is launched.
The print("Event is working") is displayed in the terminal so everything is working.
The only thing I need now is to be able to update the badge of a specific bar item.
import Foundation
import UIKit
import SwiftyJSON
class SocketIOManager: NSObject{
func connectedToSocketIo(){
socket.on("post-channel:App\\Events\\contact\\newContactRequest"){ (data, ack) -> Void in
let json = JSON(data)
if json[0]["id"].string! == self.defaults.stringForKey("user_id")! {
print("event is working")
// I want to change the tab bar item badge here
} else {
print("no event")
}
}
}
}
You should try to get a reference to the UITabBarController in your SocketIOManager class. Once you have a reference the tab bar controller you can change the badge value of the desired UITabBarItem.
import Foundation
import UIKit
import SwiftyJSON
class SocketIOManager: NSObject {
/*
var tabBarController: UITabBarController!
*/
// When the tabBarController gets set the connectedToSocketIO function gets automatically called.
var tabBarController: UITabBarController! {
didSet {
connectedToSocketIO()
}
}
init() {
super.init()
}
// Either call this function
init(tabBarController: UITabBarController) {
super.init()
self.tabBarController = tabBarController
connectedToSocketIO()
}
// Or create a setter
func setTabBarController(tabBarController: UITabBarController) {
self.tabBarController = tabBarController
}
func connectedToSocketIo() {
socket.on("post-channel:App\\Events\\contact\\newContactRequest"){ (data, ack) -> Void in
let json = JSON(data)
if json[0]["id"].string! == self.defaults.stringForKey("user_id")! {
print("event is working")
// Set the desired tab bar item to a given value
tabBarController!.tabBar.items![0].badgeValue = "1"
} else {
print("no event")
}
}
}
}
EDIT
class CustomTabBarController: UITabBarController {
var socketIOManager: SocketIOManager!
viewDidLoad() {
super.viewDidLoad()
socketIOManager = SocketIOManager(tabBarController: self)
}
}
Hope this helps!
#Jessy Naus
I removed:
the socket connection from the app delegate,
the override init function inside the socketIOManager so the init(UITabBarController)
and added the socket.connect() (from socket.io library) function inside the init function linked to the tab bar controller as follow:
init(tabBarController: UITabBarController) {
super.init()
self.tabBarController = tabBarController
socket.connect()
self.listeningToSocketEvent()
}
I have replaced "self.connectedToSocketIo()" by "listeningToSocketEvent()" has the meaning of this function is more clear.
All together following your instructions mentioned above = Works perfectly. So I put your answer as the good one.
Really not easy concept. Will still need some time to assimilate it and apply it to other components of the UI.
Thanks a lot for your help on this!
actually, I found another way which avoid touching my socket.io instance.
Source:
Swift 2: How to Load UITabBarController after Showing LoginViewController
I just make the link with my tab bar controller as follow:
In my SocketIOManager
//"MainTabBarController" being the UITabBarController identifier I have set in the storyboard.
//TabBarController being my custom UITabBarController class.
// receivedNotification() being a method defined in my custom TabBarController class
let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
let tabBarController: TabBarController = mainStoryboard.instantiateViewControllerWithIdentifier("MainTabBarController") as! TabBarController
tabBarController.receivedNotification(1)
In my TabBarController class:
func receivedNotification(barItem: Int){
if let actualValue = self.tabBar.items![barItem].badgeValue {
let currentValue = Int(actualValue)
self.tabBar.items![barItem].badgeValue = String(currentValue! + 1)
} else {
self.tabBar.items![barItem].badgeValue = "1"
}
// Reload tab bar item
let appDelegate = UIApplication.sharedApplication().delegate as! AppDelegate
appDelegate.window?.rootViewController = self
}
I have Tap Bar Controller with 2 paths. One is settingController Other one is loginController and contactListController.
When i run the program the entry pint is set tocontactListControllerand if login is false apps shownloginController`. After login value is set on true and loginController is dismiss. On bottom i have Tab Bar Controller: ContactList | Settings
When i go to settings i have a LOGOUT button, i would like to do when i tap this how to set value login on false ? i have no segue between ContactList and SettingController
This is my ContactListController
class ContactsTableViewController: UITableViewController, SettingsControllerDelegate {
let settingsController: SettingsController = UIStoryboard(name: "Main", bundle: nil).instantiateViewControllerWithIdentifier("settingsController") as! SettingsController
override func viewDidLoad() {
super.viewDidLoad()
settingsController.delegate = self
}
func didLogoutSuccessfully() {
loggedIn = false
}
}
This is settings controller
protocol SettingsControllerDelegate {
func didLogoutSuccessfully()
}
class SettingsController: UITableViewController {
var delegate: SettingsControllerDelegate?
fun tapButton() {
self.delegate?.didLogoutSuccessfully() // Set login as false
}
if i added
override func viewDidLoad() {
super.viewDidLoad(
settingsController.delegate = self
presentViewController(settingsController, animated: true, completion: nil)
}
my controller setting is appear first. How can i change this value in other way?
UPDATE
in contact list i have
var loggedIn: Bool = false {
didSet {
if loggedIn == true {
self.configureView()
}
}
}
override func viewDidAppear(animated: Bool) {
if loggedIn == false {
performSegueWithIdentifier("showLogin", sender: nil)
}
//tableView.reloadData()
}
Consider either 1: using notifications (to which all interested controllers are registered as observers) to react to session state changes, 2: moving your session state to something "higher up the chain" (like in or "hanging off of" your app delegate), or 3: making a singleton session controller.
1 can be used with 2 and 3 and either 2 or 3 make accessing the current state from anywhere in your app easier. I'd go with a mix of 1 and 3 myself.
This approach in general relieves you from having to walk and inspect the controller hierarchy to find and set the same thig on all other controllers (which is icky because it's so tightly coupled; changing the hierarchy and/or reusing VCs elsewhere would probably break things).
You can pass data between the tabs using UITabViewControllers.viewControllers method which returns array of the view controllers in the tab
//in SettingsVC
func viewWillDisapear(){
//assuming its in the second index of tabBar
let contactVC = self.tabBarController.viewControllers[1] as ContactsTableViewController
contactVC.delegate = self
contactVC.loggedIn = true //or false as you wish
super.viewWillDisapear()
}
I am getting "unexpectedly found nil while unwrapping an Optional value" because in my code below I am trying to assign value to webview before its initialize. I am trying to transition from Master to Detail view controller.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "showDetail" {
if let indexPath = self.tableView.indexPathForSelectedRow() {
let object = self.fetchedResultsController.objectAtIndexPath(indexPath) as NSManagedObject
let controller = (segue.destinationViewController as UINavigationController).topViewController as DetailViewController
controller.detailItem = object
controller.navigationItem.leftBarButtonItem = self.splitViewController?.displayModeButtonItem()
controller.navigationItem.leftItemsSupplementBackButton = true
}
}
}
Detail View Code:
var detailItem: AnyObject? {
didSet {
// Update the view.
self.configureView()
}
}
func configureView() {
// Update the user interface for the detail item.
if let detailContent = detailItem?.valueForKey("content") as? String{
self.webView.loadHTMLString(detailContent as String, baseURL:nil)
}
}
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
self.configureView()
}
It is failing because my Webview in Nil. How do I come around this situation where my outlets are not initialized while setting them.
Please help.
Thanks.
Stop and think about the order in which things happen:
prepareForSegue - The destination view controller exists, but that's all. It has no view and its outlets have not been set. You can set its non-outlet properties but that's all you can do.
The segue starts to happen.
The destination view controller gets viewDidLoad. Now it has a view and its outlets are set.
The segue completes and the destination view controller gets viewWillAppear: and later, viewDidAppear:. Now its view is actually in the interface.
So clearly you cannot permit configureView to assume that the web view exists, because the first time it is called, namely in prepareForSegue, it doesn't exist. configureView needs to test explicitly whether self.webView is nil, and if it is, it should do nothing:
func configureView() {
// Update the user interface for the detail item.
if self.webView == nil { return } // no web view, bail out
if let detailContent = detailItem?.valueForKey("content") as? String{
self.webView.loadHTMLString(detailContent as String, baseURL:nil)
}
}
After that, everything will be fine. viewDidLoad will subsequently be called, and configureView will be called again - and this time, both detailItem and the web view exist, so all will be well.