How to pass data when the back button clicked? - ios

I'm trying to pass data from UITableview to another UITableview, I succeed to pass data when I press on cell but I couldn't pass data back when I press on back button of navigation bar; I've tried global variables to solve this problem but since I'm storing date of those variables in database it causes a lot of problems to me, because it enforces all stored reminders to save the same data, I could to do some tricks to solve this problem but we all know that global variable is bad practice and does't confirm to OOP neither MVC, the question is how to pass data back with using Prepare for segue function; note that the table view are static not dynamic.
and if your were asking what data I'm trying to pass is days of week, when Friday and Saturday are selected for example it sends back true values to previous view and if Friday and Saturday are deselected false values are sent back to previous view
so how can I solve this problem?
thanks in advance

You need to do four things:
First
You should have a custom protocol such as:
public protocol DataBackDelegate: class {
func savePreferences (preferencesRestaurantsArray : [Bool], preferencesCusinesArray : [Bool])
}
as you see, I supposed that you want to send back two arrays, but you can edit that in order to send whatever data and datatypes you want.
Second
Your first view controller (or table view controller since table view controller is just a subclass of view controller) has to conform to your custom protocol, such as:
class MainTableViewController: UITableViewController, DataBackDelegate
Third
In your second view controller, you need to have a variable for that protocol, such as:
weak var delegate: DataBackDelegate?
and then you catch the back action and inside it you call your custom protocol function, such as:
self.delegate?.savePreferences(Preferences2ViewController.preferencesRestaurantsArray, preferencesCusinesArray: Preferences2ViewController.preferencesCusinesArray)
Fourth
In your first main controller, in the segue that fires the second view controller, you should set the deleage to self, such as:
destination.dataBackDelegate = self
where destination is the second view controller

I don't have implement the tableviews, I just show you the concept.
VIEWCONTROLLER A (first UITableView) :
import UIKit
class vc1: UIViewController {
//Just to store days and the selected state (at start they should be unselected I presume)
var selectedDays : [String : Bool] = [
"Monday":false,
"Tuesday":false,
"Wednesday":false,
"Thursday":false,
"Friday":false,
"Saturday":false,
"Sunday": false
]
override func viewDidLoad() {
super.viewDidLoad()
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
//set this current view controller to the other UIViewController which will be pushed (vc2)
//You will need it later when pass back data
let secondViewController = segue.destinationViewController as! vc2
secondViewController.previousVC = self
}
}
VIEWCONTROLLER B (your 2nd UITableView) :
class vc2: UIViewController {
var previousVC : ViewController
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewWillDisappear(animated: Bool) {
super.viewWillDisappear(true)
//Suppose that I selected the day of monday and the day thursday
//get the datasource from the previousVC UIViewController and set the correct selected days
previousVC.selectedDays["monday"] = true
previousVC.selectedDays["thursday"] = true
//Here your previousVC selectedDays dictionary variable contains now the new values
//So you can do all you want with it when you will come back on your previous viewcontroller
/*
var selectedDays : [String : Bool] = [
"Monday":true,
"Tuesday":false,
"Wednesday":false,
"Thursday":true,
"Friday":false,
"Saturday":false,
"Sunday": false
]
*/
}
}
Is this what you wanted ?

Related

Is there a way to pass data back to a view controller when swiping down to dismiss another view controller?

I have a view controller, lets call it vc1, which passes some data to another (vc2) using prepare for segue, and then calling performSegue.
Is there a way to pass some data back from vc2 to vc1 when vc2 is dismissed by swiping down?
Thanks,
Edit --
Apologies for the lack of information, very new to swift so unsure of the correct question to ask in this situation.
To elaborate, the root of the issue at the moment is that vc2 is not dismissed programatically. ie there is currently no function called, it is simply dismissed by the user swiping down.
Is there some function that I can include to capture this dismissal, and use it to send data back to vc1?
I would prefer not to add any buttons to vc2 if possible.
Apologies again, and I appreciate all the help given already!
Try This
class VCOne: UIViewController {
//Create a shared instance of VCOne
static var sharedInstance:VCOne?
//Let the data to be passed back to VCOne is of type string
var dataToBePassedBack:String?
override func viewDidLoad() {
super.viewDidLoad()
//set the sharedInstance to self
VCOne.sharedInstance = self
}
}
Class VCTwo:UIViewController{
//function in which you are dismissing your current VC you can use the shared
instance to pass the data back
func dismissVC(){
//before dismissing the VCTwo you can set the value for VCOne
VCOne.sharedInstance?.dataToBePassedBack = "data"
}
}
Using Protocol And Delegate You Do or Other Option is NSotificationcenter.
One way yo do it is to create another file that it the controller of everything and then have a delegate that always notifies the view controllers when new changes are available. I will walk it through.
protocol HeadControllerDelegate {
// Create a function that sends out the data to the delegates when it is called
// You can use your custom struct here to pass more data easly
func didReciveNewData(myData: String?)
}
struct HeadController {
// Create a shared instance so that the viewcontroller that conforms to the view as well as when we sends out the data the delegate is correct
static var shared = HeadController()
// Creates the delegate, every view can asign it to
public var delegate: HeadControllerDelegate?
// Add all your values here you want to pass back
var myValue: String? {
// The didSet gets called every time this value is set, and then is it time to call the delegate method
didSet {
// Calls the delegates didReciveMethod to notify the delegates that new data exsists
delegate?.didReciveNewData(myData: myValue)
}
}
}
Now in your viewcontroller class where you would like the data to be avaiable (as you said when you swipe down)
class ViewController: UIViewController {
// Here you create a property of the shared instance
let headController = HeadController.shared
override func viewDidLoad() {
super.viewDidLoad()
// Set yourself as the delegate for the headController delegate to recive data
headController.delegate = self
}
}
extension ViewController: HeadControllerDelegate {
// here will the data be recived
func didReciveNewData(myData: String?) {
// handle the data here, you have now got newData
print(myData)
}
}
In the class where you want to pass data you just do it like this. The beauty of this is that you can have multiple classes or structs that writes to the head controllers data (just make sure you do it thought the shared instance). It is also a good pracice according to we to use the delegate pattern.
class Sender {
var headController = HeadController.shared
func sendData(data: String) {
// Here you change the data of the headcontroller wich will send the data to all the delegates
headController.myValue = data
}
}
Hope this answer helps. If you have any questions please let me know.
UPDATE -- EASIER SOLUTION
Here is an easier solution but is less scalable as the previous one according to me.
In prepareForSegue simply pass over your current viewContorller as a field in the destination view controller. Then when viewDidDissapear in the new view controller you can simply pass back the data. Not to worry, I will show you!
In prepare for Segue
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let dc = segue.destination as? SecondViewController {
dc.viewController = self
}
}
And declare the secondViewContorller as following. The ViewDidDisappear method will be called when the view has dismissed, and therefore can you pass over the data to the view controller you have set before using the prepare for segue method.
class SecondViewController: UIViewController {
var viewController: UIViewController?
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidDisappear(_ animated: Bool) {
(viewController as? ViewController)?.value = 2
}
}
Then you could update the UI using a didSet, which simply will be called when the property is set, which will be done in the view did disappear method.
var value: Int = 0 {
didSet {
print(value)
text?.text = "\(value)"
}
}
Hope this helps!

Passing variables back from a ViewController to a previous one, but variables not updating?

I have two view controllers which I am interested in passing variables from one view controller to the next in a backwards manner. To achieve this I used a protocol, however, the variable in the first view controller are not updating when going back from view controller two to view controller one:
Below is my code for the first view controller:
import UIKit
class BlueBookUniversalBeamsVC: UIViewController {
var lastSelectedTableRowByTheUser: Int = 0
var lastSelectedTableSectionByTheUser: Int = 0
override func viewDidLoad() {
super.viewDidLoad()
print(lastSelectedTableRowByTheUser)
print(lastSelectedTableSectionByTheUser)
}
}
extension BlueBookUniversalBeamsVC: ProtocolToPassDataBackwardsFromDataSummaryVcToPreviousVc {
func dataToBePassedUsingProtocol(passedSelectedTableSectionNumberFromPreviousVc: Int, passedSelectedTableRowNumberFromPreviousVc: Int) {
self.lastSelectedTableRowByTheUser = passedSelectedTableRowNumberFromPreviousVc
self.lastSelectedTableSectionByTheUser = passedSelectedTableSectionNumberFromPreviousVc
print("Last selected row passed back from SummaryVC is equal to \(passedSelectedTableRowNumberFromPreviousVc)")
print("Last selected section passed back from SummaryVC is equal to \(passedSelectedTableSectionNumberFromPreviousVc)")
}
Below is my code inside the second view controllerL
import UIKit
class BlueBookUniversalBeamDataSummaryVC: UIViewController {
var delegate: ProtocolToPassDataBackwardsFromDataSummaryVcToPreviousVc?
#objc func navigationBarLeftButtonPressed(sender : UIButton) {
let main = UIStoryboard(name: "Main", bundle: nil)
let previousViewControllerToGoTo = main.instantiateViewController(withIdentifier: "BlueBookUniversalBeamsVC")
if delegate != nil {
delegate?.dataToBePassedUsingProtocol(passedSelectedTableSectionNumberFromPreviousVc: self.selectedTableSectionNumberFromPreviousViewController, passedSelectedTableRowNumberFromPreviousVc: self.selectedTableRowNumberFromPreviousViewController)
}
self.present(previousViewControllerToGoTo, animated: true, completion: nil)
}
}
The weird thing is that in Xcode console when I go back from VC2 to VC1, inside the protocol function extension in VC1 I can see the values being printed correctly. However, when the values get printed from inside viewDidLoad() both of them are showing as 0. Any idea why this is happening, is there something I am missing out here?
Your second view controller is instantiating a new instance of the first view controller rather than using the instance that was already there. The second view controller shouldn’t present the first view controller again, but rather dismiss (or pop) back to it, depending upon the first presented or pushed to it.
By the way, the delegate property of the second view controller that points back to the first one should be a weak property. You never want a child object maintaining a strong reference to a parent object. Besides, delegates are almost always weak...

How would you save(append) data from one View Controller to another View Controller when you segue from a different view controller?

Sorry, the question is a bit long. Please bear with me.
Basically, I'm trying to write a simple count up/count down ios app using swift. I have three main view controllers. One is an "Initial View Controller" (which is the root view controller) that contain only two buttons - one that presents modally to the actual counting page (second view controller) and another present modally to a tableViewController page (third view controller). so those are the three view controllers.
So, if the user chooses to save the counter they have been counting I want to append the data on that counter view controller to an array I have created to be displayed on the tableViewController. So I'm making the tableViewController a delegate of the Counter View Controller to append the data to the array.
And as to my understanding, you need to implement prepareSegue in tableViewController to connect the tableViewController to the Counter View Controller. However, because the segue to the Counter View Controller doesn't originate from the tableViewController and instead from the Initial View Controller, the prepareSegue function is not working, and thus the delegate doesn't work. So to simplify my question- How would you save(append) data from one View Controller to another View Controller when you segue from a different view controller?
I hope my question was clear. I'm completely new to software development and not sure if I'm making any sense. Thanks so much for the help!
If you have three controllers in the storyboard path, One -> Two -> Three, and you want One to know about data changes in Three, then you need to propagate the changes via Two.
A rough version might look like this:
protocol CountDelegate: class {
func updateCount()
}
class One: UIViewController, CountDelegate {
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
guard let destination = segue.destination as? Two else { return }
destination.delegate = self
}
func updateCount() {
// whatever
}
}
class Two: UIViewController {
weak var delegate: CountDelegate?
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
guard let destination = segue.destination as? Three else { return }
destination.delegate = self.delegate // just pass the delegate down
}
}
class Three: UIViewController {
weak var delegate: CountDelegate?
func doWork() {
self.delegate?.updateCount()
}
}
So the delegate is One, and both Two and Three (via Two) point back to it as the delegate.
Solution 1 (Using Notifications):
Each time the counter is updated in CounterViewController, the following code needs to be executed:
let notification = Notification.init(name: NSNotification.Name(rawValue: "UpdateCounter"), object: NSNumber.init(value: 1), userInfo: nil)
NotificationCenter.default.post(notification)
This code is implemented in the Initial View Controller (to observe for the changes in counter):
override func viewDidLoad() {
super.viewDidLoad()
NotificationCenter.default.addObserver(self, selector: #selector(parseNotification(_:)), name: NSNotification.Name.init(rawValue: "UpdateCounter"), object: nil)
}
func parseNotification(_ notification: Notification?) {
if let number = notification?.object as? NSNumber {
/** here counter is a class variable in Initial ViewController **/
counter = number.intValue
}
}
And add the following code in prepareforSegue in the Initial View Controller
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
//Condition to check if TableViewController is being opened
tableViewController.counter = counter
}
Don't forget to remove the observer in the Initial View Controller:
deinit {
NotificationCenter.default.removeObserver(self)
}
Solution 2 (Using Global/Shared variables):
Create a global/shared variable such as
class Shared {
var value = 0
let instance = Shared()
}
In the CounterViewController, you set the value every time the counter is updated
Shared.instance.value = counterValue
You can read the value in TableViewController using the following code:
Shared.instance.value

Make a segmented control change the value for another VC [duplicate]

Say I have multiple view controllers in my Swift app and I want to be able to pass data between them. If I'm several levels down in a view controller stack, how do I pass data to another view controller? Or between tabs in a tab bar view controller?
(Note, this question is a "ringer".) It gets asked so much that I decided to write a tutorial on the subject. See my answer below.
Your question is very broad. To suggest there is one simple catch-all solution to every scenario is a little naïve. So, let's go through some of these scenarios.
The most common scenario asked about on Stack Overflow in my experience is the simple passing information from one view controller to the next.
If we're using storyboard, our first view controller can override prepareForSegue, which is exactly what it's there for. A UIStoryboardSegue object is passed in when this method is called, and it contains a reference to our destination view controller. Here, we can set the values we want to pass.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "MySegueID" {
if let destination = segue.destination as? SecondController {
destination.myInformation = self.myInformation
}
}
}
Alternatively, if we're not using storyboards, then we're loading our view controller from a nib. Our code is slightly simpler then.
func showNextController() {
let destination = SecondController(nibName: "SecondController", bundle: nil)
destination.myInformation = self.myInformation
show(destination, sender: self)
}
In both cases, myInformation is a property on each view controller holding whatever data needs to be passed from one view controller to the next. They obviously don't have to have the same name on each controller.
We might also want to share information between tabs in a UITabBarController.
In this case, it's actually potentially even simpler.
First, let's create a subclass of UITabBarController, and give it properties for whatever information we want to share between the various tabs:
class MyCustomTabController: UITabBarController {
var myInformation: [String: AnyObject]?
}
Now, if we're building our app from the storyboard, we simply change our tab bar controller's class from the default UITabBarController to MyCustomTabController. If we're not using a storyboard, we simply instantiate an instance of this custom class rather than the default UITabBarController class and add our view controller to this.
Now, all of our view controllers within the tab bar controller can access this property as such:
if let tbc = self.tabBarController as? MyCustomTabController {
// do something with tbc.myInformation
}
And by subclassing UINavigationController in the same way, we can take the same approach to share data across an entire navigation stack:
if let nc = self.navigationController as? MyCustomNavController {
// do something with nc.myInformation
}
There are several other scenarios. By no means does this answer cover all of them.
This question comes up all the time.
One suggestion is to create a data container singleton: An object that gets created once and only once in the life of your application, and persists for the life of your app.
This approach is well suited for a situation when you have global app data that needs to be available/modifiable across different classes in your app.
Other approaches like setting up one-way or 2-way links between view controllers are better suited to situations where you are passing information/messages directly between view controllers.
(See nhgrif's answer, below, for other alternatives.)
With a data container singleton, you add a property to your class that stores a reference to your singleton, and then use that property any time you need access.
You can set up your singleton so that it saves it's contents to disk so that your app state persists between launches.
I created a demo project on GitHub demonstrating how you can do this. Here is the link:
SwiftDataContainerSingleton project on GitHub
Here is the README from that project:
SwiftDataContainerSingleton
A demonstration of using a data container singleton to save application state and share it between objects.
The DataContainerSingleton class is the actual singleton.
It uses a static constant sharedDataContainer to save a reference to the singleton.
To access the singleton, use the syntax
DataContainerSingleton.sharedDataContainer
The sample project defines 3 properties in the data container:
var someString: String?
var someOtherString: String?
var someInt: Int?
To load the someInt property from the data container, you'd use code like this:
let theInt = DataContainerSingleton.sharedDataContainer.someInt
To save a value to someInt, you'd use the syntax:
DataContainerSingleton.sharedDataContainer.someInt = 3
The DataContainerSingleton's init method adds an observer for the UIApplicationDidEnterBackgroundNotification. That code looks like this:
goToBackgroundObserver = NSNotificationCenter.defaultCenter().addObserverForName(
UIApplicationDidEnterBackgroundNotification,
object: nil,
queue: nil)
{
(note: NSNotification!) -> Void in
let defaults = NSUserDefaults.standardUserDefaults()
//-----------------------------------------------------------------------------
//This code saves the singleton's properties to NSUserDefaults.
//edit this code to save your custom properties
defaults.setObject( self.someString, forKey: DefaultsKeys.someString)
defaults.setObject( self.someOtherString, forKey: DefaultsKeys.someOtherString)
defaults.setObject( self.someInt, forKey: DefaultsKeys.someInt)
//-----------------------------------------------------------------------------
//Tell NSUserDefaults to save to disk now.
defaults.synchronize()
}
In the observer code it saves the data container's properties to NSUserDefaults. You can also use NSCoding, Core Data, or various other methods for saving state data.
The DataContainerSingleton's init method also tries to load saved values for it's properties.
That portion of the init method looks like this:
let defaults = NSUserDefaults.standardUserDefaults()
//-----------------------------------------------------------------------------
//This code reads the singleton's properties from NSUserDefaults.
//edit this code to load your custom properties
someString = defaults.objectForKey(DefaultsKeys.someString) as! String?
someOtherString = defaults.objectForKey(DefaultsKeys.someOtherString) as! String?
someInt = defaults.objectForKey(DefaultsKeys.someInt) as! Int?
//-----------------------------------------------------------------------------
The keys for loading and saving values into NSUserDefaults are stored as string constants that are part of a struct DefaultsKeys, defined like this:
struct DefaultsKeys
{
static let someString = "someString"
static let someOtherString = "someOtherString"
static let someInt = "someInt"
}
You reference one of these constants like this:
DefaultsKeys.someInt
Using the data container singleton:
This sample application makes trival use of the data container singleton.
There are two view controllers. The first is a custom subclass of UIViewController ViewController, and the second one is a custom subclass of UIViewController SecondVC.
Both view controllers have a text field on them, and both load a value from the data container singlelton's someInt property into the text field in their viewWillAppear method, and both save the current value from the text field back into the `someInt' of the data container.
The code to load the value into the text field is in the viewWillAppear: method:
override func viewWillAppear(animated: Bool)
{
//Load the value "someInt" from our shared ata container singleton
let value = DataContainerSingleton.sharedDataContainer.someInt ?? 0
//Install the value into the text field.
textField.text = "\(value)"
}
The code to save the user-edited value back to the data container is in the view controllers' textFieldShouldEndEditing methods:
func textFieldShouldEndEditing(textField: UITextField) -> Bool
{
//Save the changed value back to our data container singleton
DataContainerSingleton.sharedDataContainer.someInt = textField.text!.toInt()
return true
}
You should load values into your user interface in viewWillAppear rather than viewDidLoad so that your UI updates each time the view controller is displayed.
Another alternative is to use the notification center (NSNotificationCenter) and post notifications. That is a very loose coupling. The sender of a notification doesn't need to know or care who's listening. It just posts a notification and forgets about it.
Notifications are good for one-to-many message passing, since there can be an arbitrary number of observers listening for a given message.
Swift 4
There are so many approaches for data passing in swift. Here I am adding some of the best approaches of it.
1) Using StoryBoard Segue
Storyboard segues are very much useful for passing data in between Source and Destination View Controllers and vice versa also.
// If you want to pass data from ViewControllerB to ViewControllerA while user tap on back button of ViewControllerB.
#IBAction func unWindSeague (_ sender : UIStoryboardSegue) {
if sender.source is ViewControllerB {
if let _ = sender.source as? ViewControllerB {
self.textLabel.text = "Came from B = B->A , B exited"
}
}
}
// If you want to send data from ViewControllerA to ViewControllerB
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.destination is ViewControllerB {
if let vc = segue.destination as? ViewControllerB {
vc.dataStr = "Comming from A View Controller"
}
}
}
2) Using Delegate Methods
ViewControllerD
//Make the Delegate protocol in Child View Controller (Make the protocol in Class from You want to Send Data)
protocol SendDataFromDelegate {
func sendData(data : String)
}
import UIKit
class ViewControllerD: UIViewController {
#IBOutlet weak var textLabelD: UILabel!
var delegate : SendDataFromDelegate? //Create Delegate Variable for Registering it to pass the data
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
textLabelD.text = "Child View Controller"
}
#IBAction func btnDismissTapped (_ sender : UIButton) {
textLabelD.text = "Data Sent Successfully to View Controller C using Delegate Approach"
self.delegate?.sendData(data:textLabelD.text! )
_ = self.dismiss(animated: true, completion:nil)
}
}
ViewControllerC
import UIKit
class ViewControllerC: UIViewController , SendDataFromDelegate {
#IBOutlet weak var textLabelC: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view.
}
#IBAction func btnPushToViewControllerDTapped( _ sender : UIButton) {
if let vcD = self.storyboard?.instantiateViewController(withIdentifier: "ViewControllerD") as? ViewControllerD {
vcD.delegate = self // Registring Delegate (When View Conteoller D gets Dismiss It can call sendData method
// vcD.textLabelD.text = "This is Data Passing by Referenceing View Controller D Text Label." //Data Passing Between View Controllers using Data Passing
self.present(vcD, animated: true, completion: nil)
}
}
//This Method will called when when viewcontrollerD will dismiss. (You can also say it is a implementation of Protocol Method)
func sendData(data: String) {
self.textLabelC.text = data
}
}
Instead of creating a data controller singelton I would suggest to create a data controller instance and pass it around. To support dependency injection I would first create a DataController protocol:
protocol DataController {
var someInt : Int {get set}
var someString : String {get set}
}
Then I would create a SpecificDataController (or whatever name would currently be appropriate) class:
class SpecificDataController : DataController {
var someInt : Int = 5
var someString : String = "Hello data"
}
The ViewController class should then have a field to hold the dataController. Notice that the type of dataController is the protocol DataController. This way it's easy to switch out data controller implementations:
class ViewController : UIViewController {
var dataController : DataController?
...
}
In AppDelegate we can set the viewController's dataController:
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
if let viewController = self.window?.rootViewController as? ViewController {
viewController.dataController = SpecificDataController()
}
return true
}
When we move to a different viewController we can pass the dataController on in:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
...
}
Now when we wish to switch out the data controller for a different task we can do this in the AppDelegate and do not have to change any other code that uses the data controller.
This is of course overkill if we simply want to pass around a single value. In this case it's best to go with nhgrif's answer.
With this approach we can separate view form the logic part.
As #nhgrif pointed out in his excellent answer, there are lots of different ways that VCs (view controllers) and other objects can communicate with each other.
The data singleton I outlined in my first answer is really more about sharing and saving global state than about communicating directly.
nhrif's answer lets you send information directly from the source to the destination VC. As I mentioned in reply, it's also possible to send messages back from the destination to the source.
In fact, you can set up an active one-way or 2-way channel between different view controllers. If the view controllers are linked via a storyboard segue, the time to set up the links is in the prepareFor Segue method.
I have a sample project on Github that uses a parent view controller to host 2 different table views as children. The child view controllers are linked using embed segues, and the parent view controller wires up 2-way links with each view controller in the prepareForSegue method.
You can find that project on github (link). I wrote it in Objective-C, however, and haven't converted it to Swift, so if you're not comfortable in Objective-C it might be a little hard to follow
SWIFT 3:
If you have a storyboard with identified segues use:
func prepare(for segue: UIStoryboardSegue, sender: Any?)
Although if you do everything programmatically including navigation between different UIViewControllers then use the method:
func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool)
Note: to use the second way you need to make your UINavigationController, you are pushing UIViewControllers on, a delegate and it needs to conform to the protocol UINavigationControllerDelegate:
class MyNavigationController: UINavigationController, UINavigationControllerDelegate {
override func viewDidLoad() {
self.delegate = self
}
func navigationController(_ navigationController: UINavigationController, willShow viewController: UIViewController, animated: Bool) {
// do what ever you need before going to the next UIViewController or back
//this method will be always called when you are pushing or popping the ViewController
}
}
It depends when you want to get data.
If you want to get data whenever you want, can use a singleton pattern. The pattern class is active during the app runtime. Here is an example of the singleton pattern.
class AppSession: NSObject {
static let shared = SessionManager()
var username = "Duncan"
}
class ViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
print(AppSession.shared.username)
}
}
If you want to get data after any action, can use NotificationCenter.
extension Notification.Name {
static let loggedOut = Notification.Name("loggedOut")
}
#IBAction func logoutAction(_ sender: Any) {
NotificationCenter.default.post(name: .loggedOut, object: nil)
}
NotificationCenter.default.addObserver(forName: .loggedOut, object: nil, queue: OperationQueue.main) { (notify) in
print("User logged out")
}
The way that I would do it would be instead of passing data between view controllers, I would just declare a variable globally. You can even do this with a function!
For example:
var a = "a"
func abc() {
print("abc")
}
class ViewController: UIViewController {
}

Eureka row to present view controller and return value in Swift 3.0

I am looking for help in figuring out how to have a row in a MultivaluedSection present a view controller with a second Eureka form and return a value back to the MultivaluedSection row. I've been able to get a regular ButtonRow to push a view controller using a segue, but I can't figure out not to get a value back to the row in the MultivaluedSection. I'm not sure if the ButtonRow method supports returning values or not so I started looking for other solutions. One I found is to use a custom presenter row (https://github.com/xmartlabs/Eureka#custom-presenter-rows), but I don't understand how to make that work.
Here one thing I did find, but again, I don't understand how to put this all together:
Help creating simple Custom Presenter Row
- https://github.com/xmartlabs/Eureka/issues/716
Can someone either point me to a working sample or help walk me through getting this setup?
If you are already pushing a new VC with a segue, then you might want to implement a protocol and define the functions to pass data back.
Here is a good tutorial with Navigation controllers where at the end a Protocol is added.
eg:
View one (could be the Form View Controller with the ButtonRow)
class FormVC: FormViewController , FooViewControllerDelegate{
var text : String!
override func viewDidLoad() {
super.viewDidLoad()
}
/// Delegate protocol callback implementation
func myVCDidFinish(controller: FooViewController, text: String) {
// Receive the data as a delegate
self.text = text
// In this case we also want to finish the view
controller.navigationController?.popViewController(animated: true)
}
/// This represents the prepare for segue mentioned as implemented in the question
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
// Act upon the segue we want from this VC
// The string is defined in the storyboard, so it must be exactly the same
if segue.identifier == "mySegue"{
// Creating the second VC instance
let vc = segue.destination as! FooViewController
// Since this class is now a delegate, setup the delegate
vc.delegate = self
}
}
}
View two (the pushed View controller)
protocol FooViewControllerDelegate {
func myVCDidFinish(controller: FooViewController, text: String)
}
class FooViewController: UIViewController {
/// Data
var text : String!
/// Set up an optional delegate
var delegate:FooViewControllerDelegate? = nil
override func viewDidLoad() {
super.viewDidLoad()
// Init label
self.text = "Pushed view data to pass back
}
}

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