I want to use Soroush Khanlou coordinator pattern (http://khanlou.com) in my iOS app. My problem is how can I pass data back to my first view controller through coordinators?
Before using the coordinator pattern, I used a delegate(protocol) to pass data back from second view controller to the first one, because my first view controller was responsible for creating and presenting the second view controller, that was not a good solution. So I decided to use coordinator
to remove the job of app navigation from my view controllers.
This is the scenario:
class FirstViewController: UIViewController {
weak var coordinator: MainCoordinator?
func showSecondViewController(data: Data) {
coordinator?.presentSecondViewController(data: data) {[weak self] in
guard let self = self else { return }
//Do something
}
}
class MainCoordinator: NSObject, Coordinator {
var childCoordinators = [Coordinator]()
var navigationController: UINavigationController
init(navigationController: UINavigationController) {
self.navigationController = navigationController
}
func start(completion: (() -> Void)?) {
navigationController.delegate = self
let firstViewController = FirstViewController.instantiate()
firstViewController.coordinator = self
navigationController.pushViewController(firstViewController, animated: false)
}
func presentSecondViewController(data: Data, completion: #escaping () -> Void) {
let child = SecondCoordinator(data: data, navigationController: navigationController)
childCoordinators.append(child)
child.parentCoordinator = self
child.start() {
completion()
}
}
func refresh(data: SomeDataType) {
//data from second view controller is here but I don't know how to pass it to my first view controller
//there is no reference to my first view controller
//what is the best way to pass data back?
}
}
class SecondCoordinator: Coordinator {
weak var parentCoordinator: MainCoordinator?
var childCoordinators = [Coordinator]()
var navigationController: UINavigationController
var data: Data!
init(navigationController: UINavigationController) {
self.navigationController = navigationController
}
convenience init(data: Data, navigationController: UINavigationController) {
self.init(navigationController: navigationController)
self.data = data
}
func start(completion: (() -> Void)?) {
let vc = SecondViewController(data: data)
vc.coordinator = self
vc.delegate = self. //here I used delegate to get data from second view controller to pass it to first view controller
navigationController.present(vc, animated: true) {
completion!()
}
}
}
extension SecondCoordinator: SecondViewControllerDelegate {
func refresh(data: SomeDataType) {
parentCoordinator?.refresh(data: data) // I need to pass this data to my first view controller
}
}
Using delegate pattern or closure callback pattern, you can pass a value from second view controller to first view controller.
If you use delegate pattern, data flow is below.
SecondViewController -> SecondViewControllerDelegate -> SecondCoordinator -> SecondCoordinatorDelegate -> FirstCoorfinator -> FirstViewController
If you use closure callback pattern, you will pass a closure as a parameter of
start method or initializer of SecondCoordinator.
Related
I want to trigger an action on button tap with my callback. Also I have presenter and coordinator. But nothing happenes. My code is not working in this closure:
startViewController.output = { [weak self] action in
switch action {
case .registrationButtonTapped:
self?.showRegistrationViewController()
case .loginButtonTapped:
self?.showLoginViewController()
}
}
In my ViewController I have enum:
enum StartViewControllerButton {
case registrationButtonTapped
case loginButtonTapped
}
callback:
var output: ((StartViewControllerButton) -> Void)?
and selectors:
#objc func registrationButtonPressed() {
startModulPresenter.openNextScreen()
self.output?(.registrationButtonTapped)
}
#objc func loginButtonPressed() {
startModulPresenter.openNextScreen()
self.output?(.loginButtonTapped)
}
My Presenter
class StartModulPresenter: StartModulPresenterProtocol {
var navigationController: UINavigationController
var coordinator: CoordinatorProtocol?
//Init
init(navigationController: UINavigationController) {
self.navigationController = navigationController
coordinator = AuthorizationCoordinator(navigationController: navigationController)
}
//Functions
func openNextScreen() {
coordinator?.start()
}
}
My Coordinator:
class AuthorizationCoordinator: RegistrationCoordinatorProtocol {
var presenter: PresenterProtocol?
var navigationController: UINavigationController
var childCoordinators: [CoordinatorProtocol] = []
//Init
init(navigationController: UINavigationController) {
self.navigationController = navigationController
}
func start() {
presenter = StartModulPresenter(navigationController: navigationController)
let startViewController = StartViewController(startModulPresenter: presenter as! StartModulPresenter)
startViewController.output = { [weak self] action in
switch action {
case .registrationButtonTapped:
self?.showRegistrationViewController()
case .loginButtonTapped:
self?.showLoginViewController()
}
}
}
private func showRegistrationViewController() {
let registrationViewController = RegistrationViewController()
registrationViewController.view.backgroundColor = .orange
self.navigationController.pushViewController(registrationViewController, animated: true)
}
private func showLoginViewController() {
let loginViewController = LoginViewController()
loginViewController.view.backgroundColor = .orange
self.navigationController.pushViewController(loginViewController, animated: true)
}
}
Could you check if startViewController is pushed/presented or not?
func start() {
presenter = StartModulPresenter(navigationController: navigationController)
let startViewController = StartViewController(startModulPresenter: presenter as! StartModulPresenter)
startViewController.output = { [weak self] action in
switch action {
case .registrationButtonTapped:
self?.showRegistrationViewController()
case .loginButtonTapped:
self?.showLoginViewController()
}
}
}
And, is self.output is nil or not? If it is nil please check your assignment call, it needed to be called before you use this variable.
#objc func loginButtonPressed() {
startModulPresenter.openNextScreen()
self.output?(.loginButtonTapped)
}
Honestly, I don't recommend you to use this design pattern, just a simple thing but the real result is too complicated.
Just use protocol-based MVC. View communicate with Controller via protocol/closure or Reactive-based with Combine (PassthroughSubject/CurrentValueSubject)
In View Controller A,
var completionBlock: (((String) -> ()))? = nil
& I am calling the completion block like(ViewController A):
if let block = completionBlock {
block("block data to pass")
}
I don't want to pass the completion data to ViewController B, instead i want to pass to ViewController C which is presenting from ViewController B.
In simple words, i want to pass the closure data to from ViewController A to ViewController C.I know how to pass data with delegates, just curious with closures?
How can we achieve that?
If this block is something that you need to pass between several viewControllers, you have few options:
1- Pass closure as a variable: Create a variable on each new ViewController in the middle of VC-A, VC-C and pass them in between
for example:
//View Controller B:
var block:(((String) -> ()))? = nil
//Pass from A-B
if let viewcontrollerB = XXXX { //instantiate ViewController B from A
viewcontrollerB.block = self.block
}
//ViewController C:
var block:(((String) -> ()))? = nil
//Pass from B-C
if let viewcontrollerC = XXXX { //instantiate ViewController C from B
viewcontrollerC.block = self.block
}
//Call the block from ViewController C
if let block = self.block {
block("block data to pass")
}
2-Pass via Notification Center
You can pass this block from Any View Controller to Any Other:
//send notification:
let notification = Notification(name: Notification.Name("pass block"), object: block, userInfo: nil)
NotificationCenter.default.post(notification)
3-Access from shared object
Use a singleton design and create a static shared object and read/write to the object from different view controllers
//AppDelegate:
static var block:(((String) -> ()))? = nil
//ViewController A:
AppDelegate.block = XXX
//ViewController C:
if let block = AppDelegate.block {
block("block data to pass")
}
This is just a sample code i quickly wrote for you, you can modify objects based on your need. Hopefully will address your problem.
import UIKit
class ViewControllerA: UIViewController {
var block:(((String) -> ()))? = { input in
print(input)
}
override func viewDidLoad() {
super.viewDidLoad()
self.title = "A"
let VCB = ViewControllerB()
let VCC = ViewControllerC()
VCC.block = block
VCB.VCC = VCC
self.navigationController?.pushViewController(VCB, animated: true)
}
}
class ViewControllerB: UIViewController {
var VCC:ViewControllerC?
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = .gray
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
if let VCC = VCC {
self.present(VCC, animated: true, completion: nil)
}
}
}
class ViewControllerC: UIViewController {
var block:(((String) -> ()))? = nil
override func viewDidLoad() {
super.viewDidLoad()
self.view.backgroundColor = .yellow
//Will run the block that has been passed
block?("test")
}
}
Consider two view controller Controller1 and Controller2, I have created a form of many UITextField in controller 1, in that when a user clicks a particular UITextField it moves to Controller2 and he selects the data there.
After selecting the data in Controller2 it automatically moves to Controller1, while returning from controller2 to controller1 other UITextfield data got cleared and only the selected data from controller2 is found. I need all the data to be found in the UITextfield after selecting.
Here is the code for returning from Controller2 to Controller1
if(Constants.SelectedComplexName != nil)
{
let storyBoard: UIStoryboard = UIStoryboard(name: "NewUserLogin", bundle: nil)
let newViewController = storyBoard.instantiateViewController(withIdentifier: "NewUser") as! NewUserRegistrationViewController
self.present(newViewController, animated: true, completion: nil)
}
To pass messages you need to implement Delegate.
protocol SecondViewControllerDelegate: NSObjectProtocol {
func didUpdateData(controller: SecondViewController, data: YourDataModel)
}
//This is your Data Model and suppose it contain 'name', 'email', 'phoneNumber'
class YourDataModel: NSObject {
var name: String? //
var phoneNumber: String?
var email: String?
}
class FirstViewController: UIViewController, SecondViewControllerDelegate {
var data: YourDataModel?
var nameTextField: UITextField?
var phoneNumberTextField: UITextField?
var emailTextField: UITextField?
override func viewDidLoad() {
super.viewDidLoad()
callWebApi()
}
func callWebApi() {
//After Success Fully Getting Data From Api
//Set this data to your global object and then call setDataToTextField()
//self.data = apiResponseData
self.setDataToTextField()
}
func setDataToTextField() {
self.nameTextField?.text = data?.name
self.phoneNumberTextField?.text = data?.phoneNumber
self.emailTextField?.text = data?.email
}
func openNextScreen() {
let vc2 = SecondViewController()//Or initialize it from storyboard.instantiate method
vc2.delegate = self//tell second vc to call didUpdateData of this class.
self.navigationController?.pushViewController(vc2, animated: true)
}
//This didUpdateData method will call automatically from second view controller when the data is change
func didUpdateData(controller: SecondViewController, data: YourDataModel) {
}
}
class SecondViewController: UIViewController {
var delegate: SecondViewControllerDelegate?
func setThisData(d: YourDataModel) {
self.navigationController?.popViewController(animated: true)
//Right After Going Back tell your previous screen that data is updated.
//To do this you need to call didUpdate method from the delegate object.
if let del = self.delegate {
del.didUpdateData(controller: self, data: d)
}
}
}
push your view controller instead of a present like this
if(Constants.SelectedComplexName != nil)
{
let storyBoard: UIStoryboard = UIStoryboard(name: "NewUserLogin", bundle: nil)
let newViewController = storyBoard.instantiateViewController(withIdentifier: "NewUser") as! NewUserRegistrationViewController
self.navigationController?.pushViewController(newViewController, animated: true)
}
and then pop after selecting your data from vc2 like this
self.navigationController?.popViewController(animated: true)
and if you are not using navigation controller then you can simply call Dismiss method
self.dismiss(animated: true) {
print("updaae your data")
}
There are a few ways to do it, but it usually depends on how you move from VC#1 to VC#2 and back.
(1) The code you posted implies you have a Storyboard with both view controllers. In this case create a segue from VC#1 to VC#2 and an "unwind" segue back. Both are fairly easy to do. The link provided in the comments does a good job of showing you, but, depending on (1) how much data you wish to pass back to VC#1 and (2) if you wish to execute a function on VC#2, you could also do this:
VC#1:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "ShowVC2" {
if let vc = segue.destination as? VC2ViewController {
vc.VC1 = self
}
}
}
VC#2:
weak var VC1:VC1ViewController!
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
if isMovingFromParentViewController {
VC1.executeSomeFunction()
}
}
Basically you are passing the entire instance of VC1 and therefore have access to everything that isn't marked private.
(2) If you are presenting/dismissing VC#2 from VC#1, use the delegate style as described by one of the answers.
VC#1:
var VC2 = VC2ViewController()
extension VC1ViewController: VC2ControlllerDelegate {
func showVC2() {
VC2.delegate = self
VC2.someData = someData
present(VC2, animated: true, completion: nil)
}
function somethingChanged(sender: VC2ViewController) {
// you'll find your data in sender.someData, do what you need
}
}
VC#2:
protocol VC2Delegate {
func somethingChanged(sender: VC2ViewController) {
delegate.somethingChanged(sender: self)
}
}
class DefineViewController: UIViewController {
var delegate:DefineVCDelegate! = nil
var someData:Any!
func dismissMe() {
delegate.somethingChanged(sender: self)
dismiss(animated: true, completion: nil)
}
}
}
Basically, you are making VC#1 be a delegate to VC2. I prefer the declaration syntax in VC#2 for `delegate because if you forget to set VC#1 to be a delegate for VC#2, you test will force an error at runtime.
I found Router in Clean Swift architecture is responsible to navigate and pass data between view controllers. Some samples and articles depict that Routers use segue to communicate with view controllers. What would be the convenient design when I don't want to use any segue from Storyboard. Is it possible to pass data without segue in Clean Swift? If you describe with simplest complete example, would be appreciated.
Article says that you can:
// 2. Present another view controller programmatically
You can use this to manually create, configure and push viewController.
Example.
Let's pretend that you have ViewController with button (handle push):
final class ViewController: UIViewController {
private var router: ViewControllerRouterInput!
override func viewDidLoad() {
super.viewDidLoad()
router = ViewControllerRouter(viewController: self)
}
#IBAction func pushController(_ sender: UIButton) {
router.navigateToPushedViewController(value: 1)
}
}
This ViewController has router that implements ViewControllerRouterInput protocol.
protocol ViewControllerRouterInput {
func navigateToPushedViewController(value: Int)
}
final class ViewControllerRouter: ViewControllerRouterInput {
weak var viewController: ViewController?
init(viewController: ViewController) {
self.viewController = viewController
}
// MARK: - ViewControllerRouterInput
func navigateToPushedViewController(value: Int) {
let pushedViewController = PushedViewController.instantiate()
pushedViewController.configure(viewModel: PushedViewModel(value: value))
viewController?.navigationController?.pushViewController(pushedViewController, animated: true)
}
}
The navigateToPushedViewController func can takes any parameter you want (it is good to encapsulate parameters before configure new vc, so you may want to do that).
And the PushedViewController hasn't any specific implementation. Just configure() method and assert (notify you about missing configure() call):
final class PushedViewModel {
let value: Int
init(value: Int) {
self.value = value
}
}
final class PushedViewController: UIViewController, StoryboardBased {
#IBOutlet weak var label: UILabel!
private var viewModel: PushedViewModel!
func configure(viewModel: PushedViewModel) {
self.viewModel = viewModel
}
override func viewDidLoad() {
super.viewDidLoad()
assert(viewModel != nil, "viewModel is nil. You should call configure method before push vc.")
label.text = "Pushed View Controller with value: \(viewModel.value)"
}
}
Note: also, i used Reusable pod to reduce boilerplate code.
Result:
As above article explained you can use option 2/3/4 of navigateToSomewhere method as per your app design.
func navigateToSomewhere()
{
// 2. Present another view controller programmatically
// viewController.presentViewController(someWhereViewController, animated: true, completion: nil)
// 3. Ask the navigation controller to push another view controller onto the stack
// viewController.navigationController?.pushViewController(someWhereViewController, animated: true)
// 4. Present a view controller from a different storyboard
// let storyboard = UIStoryboard(name: "OtherThanMain", bundle: nil)
// let someWhereViewController = storyboard.instantiateInitialViewController() as! SomeWhereViewController
// viewController.navigationController?.pushViewController(someWhereViewController, animated: true)
}
You need pass data across protocols
protocol SecondModuleInput {
// pass data func or variable
var data: Any? { get set }
}
protocol SecondModuleOutput {
// pass data func or variable
func send(data: Any)
}
First presenter
class FirstPresenter: SecondModuleOutput {
var view: UIViewController
var secondModuleInputHandler: SecondModuleInput?
// MARK: SecondModuleInput
func send(data: Any) {
//sended data from SecondPresenter
}
}
Second presenter
class SecondPresenter: SecondModuleInput {
var view: UIViewController
var secondModuleOutputHandler: SecondModuleOutput?
static func configureWith(block: #escaping (SecondModuleInput) -> (SecondModuleOutput)) -> UIViewController {
let secondPresenter = SecondPresenter()
secondPresenter.secondModuleOutputHandler = block(secondPresenter)
return secondPresenter.view
}
// Sending data to first presenter
func sendDataToFirstPresenter(data: Any) {
secondModuleOutputHandler?.send(data: data)
}
// MARK: FirstModuleInput
var data: Any?
}
Router
class FirstRouter {
func goToSecondModuleFrom(firstPresenter: FirstPresenter, with data: Any) {
let secondPresenterView = SecondPresenter.configureWith { (secondPreseter) -> (SecondModuleOutput) in
firstPresenter.secondModuleInputHandler = secondPreseter
return firstPresenter
}
//Pass data to SecondPresenter
firstPresenter.secondModuleInputHandler?.data = data
//Go to another view controller
//firstPresenter.view.present(secondPresenterView, animated: true, completion: nil)
//firstPresenter.view.navigationController.pushViewController(secondPresenterView, animated: true)
}
}
I want to pass my data from one ViewController to another VC on VC dismiss. Is it possible?
I've tried the next method and no success:
On button click:
self.dismiss(animated: true) {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let controller = storyboard.instantiateViewController(withIdentifier: "EditViewController") as! EditViewController
controller.segueArray = [values]
}
when EditViewController appears again, my segueArray is nil there.
How can I pass my data from my ViewController to the EditViewController on dismiss?
The best way to pass data back to the previous view controller is through delegates... when going from ViewController A to B, pass view controller A as a delegate and on the viewWillDisappear method for ViewController B, call the delegate method in ViewController A.. Protocols would help define the delegate and the required methods to be implemented by previous VC. Here's a quick example:
Protocol for passing data:
protocol isAbleToReceiveData {
func pass(data: String) //data: string is an example parameter
}
Viewcontroller A:
class viewControllerA: UIViewController, isAbleToReceiveData {
func pass(data: String) { //conforms to protocol
// implement your own implementation
}
prepare(for: Segue) {
/** code for passing data **/
let vc2 = ViewCOntrollerB() /
vc2.delegate = self //sets the delegate in the new viewcontroller
//before displaying
present(vc2)
}
}
Dismissing viewcontroller:
class viewControllerB: UIViewController {
var delegate: isAbleToReceiveData
viewWillDisappear {
delegate.pass(data: "someData") //call the func in the previous vc
}
}
In the dismiss completion block, you create a new instance of the EditViewController. I assume that another EditViewController instance exists back in the navigation stack, you need to find that instance & set the segueArray to values.
That you can achieve by iterating through your navigation stack's viewcontrollers like:
viewController.navigationController?.viewControllers.forEach({ (vc) in
if let editVC = vc as? EditViewController {
editVC.segueArray = ....
}
})
But I would recommend to use the delegate pattern, like:
protocol EditViewControllerDelegate: class {
func setSegueArray(segues: [UIStoryboardSegue])
}
In the viewcontroller (call it just ViewController) where the dismiss block is, declare a delegate property:
class ViewController: UIViewController {
weak var delegate: EditViewControllerDelegate?
....
}
Then on presenting the instance of (I assume from EditViewController) ViewController set the delegate like:
...
if let vc = presentingViewController as? ViewController {
vc.delegate = self
}
And conform the EditViewController to the delegate protocol like:
extension EditViewController: EditViewControllerDelegate {
func setSegueArray(segues: [UIStoryboardSegue]) {
// Do the data setting here eg. self.segues = segues
}
}
To detect when the back button is pressed on a view controller, I just use:
override func didMove(toParentViewController parent: UIViewController?) {
guard parent == nil else { return } // Back button pressed
... // Pass on the info as shown in you example
} // didMoveToParentViewController
A generic solution: (🔸 Swift 5.1 )
/**
* Returns a ViewController of a class Kind
* ## Examples:
* UIView.vc(vcKind: CustomViewController.self) // ref to an instance of CustomViewController
*/
public static func vc<T: UIViewController>(vcKind: T.Type? = nil) -> T? {
guard let appDelegate = UIApplication.shared.delegate, let window = appDelegate.window else { return nil }
if let vc = window?.rootViewController as? T {
return vc
} else if let vc = window?.rootViewController?.presentedViewController as? T {
return vc
} else if let vc = window?.rootViewController?.children {
return vc.lazy.compactMap { $0 as? T }.first
}
return nil
}