Im using Xcode 8 and swift 3
I created a new project selecting new "Tabbed Application" when i created it. It provided two UIViewControllers embedded in one tab bar controller. I'm trying to pass two variables between the view controllers.
The problem is that the prepare for segue function is never called. I added a print statement in it that never prints. I added the prepare function in both view controllers and can tab back and forth with no prints.
Some code:
import UIKit
import MapKit
import CoreLocation
class FirstViewController: UIViewController, MKMapViewDelegate, CLLocationManagerDelegate{
#IBOutlet weak var mapView: MKMapView!
var locationManager:CLLocationManager?
var currentLocation:CLLocation?
var destPin: MapPin?
var isTracking: Bool? = false
override func viewDidLoad() {
super.viewDidLoad()
locationManager = CLLocationManager()
locationManager?.delegate = self
locationManager?.startUpdatingLocation()
locationManager?.desiredAccuracy = kCLLocationAccuracyNearestTenMeters
locationManager?.requestAlwaysAuthorization()
updateTracking()
}
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
self.currentLocation = locations[0]
}
func locationManager(_ manager: CLLocationManager, didFailWithError error: Error) {
print(error)
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
func getMapView()-> MKMapView{
return mapView
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(true)
if(self.isTracking!){
print("Istracking bool is true")
}
else{
print("Istracking bool is false")
}
updateTracking()
locationManager?.stopUpdatingLocation()
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
print("Preparing")
let barViewControllers = segue.destination as! UITabBarController
let destinationViewController = barViewControllers.viewControllers![1] as! FirstViewController
destinationViewController.destPin = self.destPin
destinationViewController.isTracking = self.isTracking
}
}
The contents of the prepare function may very well be wrong as well but without the function even being called it hardly matters. The other view controller is also embedded in the tab bar controller and also has a prepare function that does not execute.
If you'd like, its in this github repo
It is easy to do:
The result:
For example, there are FirstViewController and SecondViewController embeded in tabViewController:
In your firstViewController.swift:
import UIKit
class FirstViewController: UIViewController {
var vc1_variable:String = "first vc's variable."
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
In your secondViewController.swift:
import UIKit
class SecondViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
let first_vc:FirstViewController = self.tabBarController?.viewControllers![0] as! FirstViewController
print("\(first_vc.vc1_variable)")
}
}
Related
I want to send data to another controller without opening it.
Example
Main controller:
override func viewDidLoad() {
let vc = SecondViewController()
vc.test = "ABCDFER"
}
Second controller:
var test: String
override func viewDidLoad() {
print(test)
}
How to do it?
It works for me this way
class ViewController: UIViewController {
var otherViewController: OtherViewController!
override func viewDidLoad() {
super.viewDidLoad()
otherViewController = OtherViewController()
otherViewController.test = "ABCDFER"
}
#IBAction func press() {
self.show(self.otherViewController, sender: nil)
}
}
class OtherViewController: UIViewController {
var test: String!
override func viewDidLoad() {
super.viewDidLoad()
print(test)
}
}
In your Main controller, as soon as viewDidLoad() finishes your instance of SecondViewController is destroyed / deallocated. If you want to set a value inSecondViewController at that point, so you can "use" it later, you need to keep a reference to that instance:
So, in Main controller:
var secondVC: SecondViewController?
override func viewDidLoad() {
secondVC = SecondViewController()
secondVC.test = "ABCDFER"
}
Now, later - perhaps on a button tap - you want to use that same instance:
#IBAction func buttonTap(_ sender: Any) {
print("test in secondVC:", secondVC?.test)
}
Keep in mind the view life cycle, if the view viewDidLoad() it's only executed when loading the view through a xib or when view related actions are done with the controller, like addSubview().
The value is being passed and will not be deallocated while your main controller is alive.
You can force a lifecycle event to be called, but isn't recommended at all.
class ViewController: UIViewController {
var otherViewController: OtherViewController!
override func viewDidLoad() {
super.viewDidLoad()
otherViewController = OtherViewController()
otherViewController.test = "ABCDFER"
//Do not do this
otherViewController.viewDidLoad()
}
}
class OtherViewController: UIViewController {
var test: String!
override func viewDidLoad() {
super.viewDidLoad()
print(test)
}
}
when I perform my segue, the location is still updated in the next VC. I tried to put the startUpdatingLocation() into an other function than the super view, but nothing changed. Do you have any ideas what i can do? Grüße aus Mannheim
import UIKit
import MapKit
import CoreLocation
class uploadPrepare: UIViewController, UITextViewDelegate, CLLocationManagerDelegate {
#IBOutlet weak var weiterButton: UIButton!
let locationPrepare = CLLocationManager()
var regionPrepare: MKCoordinateRegion!
override func viewDidLoad() {
super.viewDidLoad()
locationPrepare.delegate = self
locationPrepare.desiredAccuracy = kCLLocationAccuracyBest
locationPrepare.requestWhenInUseAuthorization()
locationPrepare.startUpdatingLocation()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
func weiterButtonTapped(_ sender: UIButton){
self.locationPrepare.stopUpdatingLocation()
self.performSegue(withIdentifier: "goToMapCheck", sender: self)
}
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
let locationPrepare = locations[0]
let myLocationPrepare:CLLocationCoordinate2D = CLLocationCoordinate2DMake(locationPrepare.coordinate.latitude,locationPrepare.coordinate.longitude)
let span: MKCoordinateSpan = MKCoordinateSpanMake(0.0005,0.0005)
regionPrepare = MKCoordinateRegionMake(myLocationPrepare,span)
print("\(locationPrepare.coordinate.latitude)")
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?)
{
let uploadInterfaceGoing = segue.destination as! mapCheck
uploadInterfaceGoing.regionReceived = regionPrepare
}
}
I am trying to pass data between my two view controllers in my UIscrollview. I am trying to use delegation to send data between Viewcontroller1 and Viewcontroller2. The delegate is Viewcontroller, while the delegator is Viewcontroller1 and Viewcontroller2.
In the code posted below, when the switch in Viewcontroller1 is toggled, it makes the switch in Viewcontroller2 put to the "off" state. I keep on getting the
fatal error: unexpectedly found nil while unwrapping an Optional value
error when I run it, but I have no clue what is causing this problem. Any ideas why?
Below is the Viewcontroller that contains the Uiscrollview and the subviews/childviews
import UIKit
class ViewController: UIViewController, testing {
var vc1 = ViewController1(nibName: "ViewController1", bundle: nil)
var vc2 = ViewController2(nibName: "ViewController2", bundle: nil)
#IBOutlet weak var scrollView: UIScrollView!
func test1() {
vc2.switch2.on = false
}
override func viewDidLoad() {
super.viewDidLoad()
self.addChildViewController(vc1)
self.scrollView.addSubview(vc1.view)
vc1.didMoveToParentViewController(self)
var frame1 = vc2.view.frame
frame1.origin.x = self.view.frame.size.width
vc2.view.frame = frame1
self.addChildViewController(vc2)
self.scrollView.addSubview(vc2.view)
vc2.didMoveToParentViewController(self)
self.scrollView.contentSize = CGSizeMake(self.view.frame.size.width * 2, self.view.frame.size.height);
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
here is the Viewcontoller1 code
protocol testing{
func test1()
}
class ViewController1: UIViewController {
var delegate:testing?
#IBOutlet weak var switch1: UISwitch!
override func viewDidLoad() {
super.viewDidLoad()
let vc = ViewController()
self.delegate = vc
// Do any additional setup after loading the view.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func switch1toggled(sender: AnyObject) {
delegate?.test1()
}
/*
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
// Get the new view controller using segue.destinationViewController.
// Pass the selected object to the new view controller.
}
*/
}
and here is the Viewcontroller 2 code
import UIKit
class ViewController2: UIViewController {
#IBOutlet weak var switch2: UISwitch!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func switch2toggled(sender: AnyObject) {
}
/*
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
// Get the new view controller using segue.destinationViewController.
// Pass the selected object to the new view controller.
}
*/
}
sorry for the long post, I have been stuck for a week on how to change the state of another switch from toggling a switch in another class, and this was the most efficient way that I found
Try This:
ViewController1
class ViewController1: UIViewController {
let defaults = NSUserDefaults.standardUserDefaults()
let switch1Key = "view1Switch"
override func viewWillAppear(animated: Bool) {
view1Switch.on = defaults.boolForKey(switch1Key)
}
#IBOutlet weak var view1Switch: UISwitch!
#IBAction func view1SwitchChanged(sender: UISwitch) {
defaults.setBool(view1Switch.on, forKey: switch1Key)
}
}
ViewController2
class ViewController2: UIViewController {
let defaults = NSUserDefaults.standardUserDefaults()
let switch1Key = "view1Switch"
override func viewWillAppear(animated: Bool) {
view2Switch.on = defaults.boolForKey(switch1Key)
}
#IBOutlet weak var view2Switch: UISwitch!
#IBAction func view2SwitchChanged(sender: UISwitch) {
defaults.setBool(view2Switch.on, forKey: switch1Key)
}
}
This method syncs the state of the two UISwitches using viewWillAppear and NSUserdefaults. The basic thought pattern is that you save the state of the switch to NSUserdefaults so that when either ViewController1 or ViewController2 is instantiated the view1Switch or view2Switch outlet's .on property is set to the saved value.
Caveats:
The first value for the switch when ViewController1 is instantiated (in the first app run) will be off because boolForKey returns false when there is no saved value. This can be hacked by using view1Switch.on = true directly after view1Switch.on = defaults.boolForKey(switch1Key)
This method makes the switches have the same value. In order to make them have different values, you can use a ! operator like so in ViewController2 view2Switch.on = !defaults.boolForKey(switch1Key). This way switch 1 will always be the opposite of switch 2.
I recommend this method over delegation because, while delegation is powerful, its power doesn't seem needed here.
If you have any questions please ask! :D
I have the following 2 controllers listed below. I'm using delegation to try and create a progressWindow which will run code and print it nicely but where the code is arbitrary.
The closures are defined by the class conforming to the protocol (in my case SyncViewController), but I want to change the UI of the progressWindowViewController from SyncViewControllers codeToRun {} closure. How do I do this?
SyncViewController.swift
import UIKit
class SyncViewController: UIViewController, progressWindowDelegate {
var codeToRun = {
//(self as! ProgressWindowViewController).theTextView.text = "changed the text"
print("code to run")
}
var codeToCancel = {print("code to cancel")}
var titleToGive = "Starting Sync..."
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func yesSyncButtonAction(sender: UIButton) {
//Segue to the ProgressWindowViewController...
}
#IBAction func noSyncActionButton(sender: UIButton) {
tabBarController?.selectedIndex = 1 //assume back to inventory section
}
// MARK: - Navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if(segue.identifier == "SyncToProgressSegue"){
let progressWindow = segue.destinationViewController as! ProgressWindowViewController
progressWindow.controllerDelegate = self //sets the delegate so we have reference to this window still.
}
}
}
ProgressWindowViewController.swift
import UIKit
protocol progressWindowDelegate{
var titleToGive : String {get}
var codeToRun : ()->() {get}
var codeToCancel : ()->() {get}
}
class ProgressWindowViewController: UIViewController {
#IBOutlet weak var theTextView: UITextView!
#IBOutlet weak var theProgressBar: UIProgressView!
#IBOutlet weak var navItemLabel: UINavigationItem!
//Sets delegate
var controllerDelegate:progressWindowDelegate!
override func viewDidLoad() {
super.viewDidLoad()
navItemLabel.title! = controllerDelegate.titleToGive
dispatch_async(dispatch_get_main_queue(),{
self.controllerDelegate.codeToRun() //Will run code accordingly.
})
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func cancelNavItemButtonAction(sender: UIBarButtonItem) {
dispatch_async(dispatch_get_main_queue(),{
self.controllerDelegate.codeToCancel()
})
}
/*
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
// Get the new view controller using segue.destinationViewController.
// Pass the selected object to the new view controller.
}
*/
}
An example of how his might be used is downloading thousands of inventory records with images, which would print the inventory details as it grabs them into the progressWindow.
But this progressWindow could also be used for other large/small tasks that need to print particular stuff into the progressWindow textarea (like logging in and therefore coming from a different view controller than sync in my example). The idea is to make it a dynamic class.
Instead of creating a variable, just use a function/method?
override func viewDidLoad() {
super.viewDidLoad()
dispatch_async(dispatch_get_main_queue(),{
self.controllerDelegate?.codeToRun(self)
})
}
.
protocol progressWindowDelegate : class {
var titleToGive : String {get}
func codeToRun(progressWindowViewController:ProgressWindowViewController)
var codeToCancel : ()->() {get}
}
class SyncViewController: UIViewController, progressWindowDelegate {
func codeToRun(progressWindowViewController:ProgressWindowViewController) {
print("code to run")
}
Also make delegate weak and optional:
delegate weak var controllerDelegate:progressWindowDelegate? = nil
I am Created 2 Views, One is and Used Protocol and Delegate. For first view the Delegate function is not called.
My FirstView Controller : Here I am Accessing the Delegate Function.
import UIKit
class NextViewController: UIViewController,DurationSelectDelegate {
//var secondController: DurationDel?
var secondController: DurationDel = DurationDel()
#IBAction func Next(sender : AnyObject)
{
let nextViewController = DurationDel(nibName: "DurationDel", bundle: nil)
self.navigationController.pushViewController(nextViewController, animated: true)
}
override func viewDidLoad() {
super.viewDidLoad()
secondController.delegate=self
}
func DurationSelected() {
println("SUCCESS")
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
My SecondView Controller : Here I Am creating Delegate.
import UIKit
protocol DurationSelectDelegate {
func DurationSelected()
}
class DurationDel: UIViewController {
var delegate: DurationSelectDelegate?
#IBAction func Previous(sender : AnyObject) {
//let game = DurationSelectDelegate()
delegate?.DurationSelected()
self.navigationController.popViewControllerAnimated(true)
}
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
}
To me, it looks like you're pushing a view controller that you haven't actually set the delegate for. If you change your "Next" function, to include the line
nextViewController.delegate = self
You should see that the delegation works. In doing this, you can also probably remove the creation of "secondController", as it looks like that's redundant.
The naming convention you have followed would confuse fellow developers in your team. The instance should have been
let durationDel = DurationDel(nibName: "DurationDel", bundle: nil)
And then as #Eagerod mentioned, the delegate you would set is
durationDel.delegate = self