I have a storyboard with a split view. When the app starts I want to set the model for the view.
I have a simple class Day:
import Foundation
class Day: NSObject{
var date: Date
var sleep: Double
init(date: Date, sleep: Double){
self.date = date
self.sleep = sleep
super.init()
}
override convenience init(){
self.init(date: Date(), sleep: 8.0)
}
}
I have a view controller for one of the split panes:
import Cocoa
class DayViewController: NSViewController {
private var day: Day = Day()
#IBOutlet weak var sleep: NSTextField!
func set(day: Day){
self.day = day
//update()
}
// func update(){
//sleep.doubleValue = day.sleep
// }
}
I want to set the Day in the app delegate so that it displays it.
How do I get the instance of DayViewController in AppDelegate so I can set this value ?
Have you tried this ?
if window?.rootViewController is DayViewController {
guard let dayVC = window?.rootViewController as? DayViewController else {
//there was an error
return
dayVC.set(day: new Day())
}
I'm not sure if it will work. Maybe it is better to do the way #Siyavash said... put in the viewDidLoad itself.
This is what I've ended up doing. Thought it may be of interest. Still undecided as to whether this is a hack or not.
In DayViewController I set a reference to it in the AppDelegate:
override func viewDidLoad() {
super.viewDidLoad()
let app: AppDelegate = NSApplication.shared.delegate as! AppDelegate
app.dayViewController = self
}
In AppDelegate I can then set the day for the view:
var dayViewController: DayViewController?
func applicationDidFinishLaunching(_ aNotification: Notification) {
let day: Day = Day.init(date: Date(), sleep: 9.5)
dayViewController!.set(day: day)
}
As requested in a comment here’s what I do now I have more experience of swift.
The example used a simple “Day” class as my model but in my implementation the model is called “TrainingDiary”. I now have virtually nothing in my AppDelegate. Instead I did the following:
I have protocol which all the view controllers that provide a view on the model implement
protocol TrainingDiaryViewController{
func set(trainingDiary td: TrainingDiary)
}
I have my view controller for the main window which now has a TabViewController in it (rather than the split view I had but this approach would work for that).
In that view controller I have overridden prepare(for:sender:):
override func prepare(for segue: NSStoryboardSegue, sender: Any?) {
super.prepare(for: segue, sender: sender)
guard let tabViewController = segue.destinationController as? NSTabViewController else {return}
for controller in tabViewController.childViewControllers{
if let c = controller as? TrainingDiaryViewController{
trainingDiaryVCs.append(c)
}
}
}
This means I now have a reference to all view controllers that are views on a TrainingDiary
In the main view there is a TableView which I use to manage the training diaries (i.e. add, remove, select). The main view controller is set as the TableViews delegate and the TableView is set in IB to have single selection and to avoid no selection. I then implemented:
func tableViewSelectionDidChange(_ notification: Notification) {
if let trainingDiary = trainingDiarysArrayController.selectedObjects[0] as? TrainingDiary{
for c in trainingDiaryVCs{
c.set(trainingDiary: trainingDiary)
}
}
}
All works great.
Related
I am new to Swift and am building an app to learn. Right now I am making the registration section of the app.
I thought the UX would be better if there were multiple VC's asking a single question, i.e. one for your name, one for your birthdate, etc as opposed to jamming all that into a single view controller. The final view controller collects all of that information and sends a dictionary as FUser object to be saved on Firebase.
I figured I could instantiate the final view controller on each of the previous five view controllers and pass that data directly to the end. I kept getting errors and figured out that the variables were nil. It works just fine if I pass the data directly to the next view controller but it doesn't seem to let me send it several view controllers down. Obviously there's a nuance to how the memory is being managed here that I'm not tracking.
Is there a way to do what I am trying to do or do I have to pass the data through each view controller along the way?
import UIKit
class FirstViewController: UIViewController {
//MARK: - IBOutlets
#IBOutlet weak var firstNameTextField: UITextField!
//MARK: - ViewLifeCycle
override func viewDidLoad() {
super.viewDidLoad()
}
//MARK: - IBActions
#IBAction func continueToMiddleViewController(_ sender: Any) {
let vcFinal = storyboard?.instantiateViewController(withIdentifier:
"finalVC") as! finalViewController
vcFinal.firstName = firstNameTextField.text
let vc = storyboard?.instantiateViewController(withIdentifier:
"middleVC") as! middleViewController
vc.modalPresentationStyle = .fullScreen
present(vc, animated: false)
}
...
}
import UIKit
class FinalViewController: UIViewController {
var firstName: String?
...
//MARK: - ViewLifeCycle
override func viewDidLoad() {
super.viewDidLoad()
}
...
}
TL;DR: The fastest one that would solve your problem is creating a singleton
There are many strategies for this. For a starter, it might be a good idea to read some begginer articles, like this one. I can update this answer if you don't find it useful, but it'd look just like the article
Viewcontroller's variable can't be initiated until any of the init method is called.
There are detailed answers on this thread.
Passing Data between ViewControllers
Another way to approach this problem could be to make use of closures. Note that personally I've moved away from using storyboards but I'll try to explain still. Closures are also referred to as callbacks, blocks, or in some context like here - completions.
You can declare a closure like let onSubmitInfo: (String?) -> Void below, it stores a reference to a block of code that can be executed at a later stage just like a function and it takes an optional string as a parameter just like a function can.
The closures are specified in the initialisers where a block of code is passed into the respective classes below and the closures are then called in the IBActions that will trigger the block of code that is defined where the below classes are initialised:
class First: UIViewController {
// MARK: - IBOutlets
#IBOutlet weak var firstNameTextField: UITextField!
// MARK: - Properties
private let onSubmitInfo: (String?) -> Void
init(onSubmitInfo: (String?) -> Void) {
self.onSubmitInfo = onSubmitInfo
}
// MARK: - IBActions
#IBAction func continue(_ sender: Any) {
onSubmitInfo(firstNameTextField.text)
}
}
class Second: UIViewController {
// MARK: - IBOutlets
#IBOutlet weak var lastNameTextField: UITextField!
// MARK: - Properties
private let onSubmitInfo: (String?) -> Void
init(onSubmitInfo: (String?) -> Void) {
self.onSubmitInfo = onSubmitInfo
}
// MARK: - IBActions
#IBAction func continue(_ sender: Any) {
onSubmitInfo(lastNameTextField.text)
}
}
To manage showing the above views and collecting the values returned by their closures (i.e. onSubmitInfo) we create a FlowController class that will also show the next view when the closure is called.
In FlowController we define the closures or blocks of code to be executed when it is called inside the IBAction in the respective First and Second classes above.
The optional string that is provided in the respective First and Second classes is used as the (firstName) and (secondName) closure properties below:
class FlowController: UIViewController {
private var fistName: String?
private var lastName: String?
...
private func showFirstView() {
let firstViewController = First(onSubmitInfo: { (firstName) in
self.firstName = firstName
showSecondView()
})
navigationController?.pushViewController(
firstViewController,
animated: true)
}
private func showSecondView() {
let secondViewController = Second(onSubmitInfo: { (lastName) in
self.lastName = lastName
showFinalView()
})
navigationController?.pushViewController(
secondViewController,
animated: true)
}
private func showFinalView() {
let finalViewController = Final(
firstName: firstName,
lastName: lastName)
navigationController?.pushViewController(
finalViewController,
animated: true)
}
}
The FlowController finally shows the Final view controller after it has collected the firstName form the First view controller and the lastName form the Second view controller in the showFinalView function above.
class Final: UIViewController {
let firstName: String
let lastName: String
...
}
I hope this is a shove in the right direction. I have moved away from storyboards because I find creating views in code is more verbose and clear on peer reviews and it was also easier for me to manage constraints and just to manage views in general.
I want to take user settings details from this view controller and read these details to the previous view controller. I have tried many different ways, but I cannot take values until I visit this view controller
I have tried first method from this page Pass Data Tutorial
This method is also not working. I think it is very simple, but I cannot figure out the right way to do it.
class SetConvViewController: UIViewController {
var engS = "engS"
#IBOutlet weak var swithEnglish: UISwitch!
override func viewDidLoad() {
super.viewDidLoad()
if let eng2 = defaults.value(forKey: engS)
{
swithEnglish.isOn = eng2 as! Bool
}
}
let defaults = UserDefaults.standard
#IBAction func switchEng(_ sender: UISwitch) {
defaults.set(sender.isOn, forKey: engS)
}
}
If I understand you correctly from this part - „but I cannot take values until I visit this view controller” - your problem lies with the fact, that until you visit your settings, there is no value for them in UserDefaults.
If you are reading them using getObject(forKey:) method, I’d recommend you to switch to using getBool(forKey:), since it will return false even if the value has not been set yet for that key ( docs )
Anyhow, if you want to set some default/initial values you can do so in your didFinishLaunching method in AppDelegate :
if UserDefaults.standard.object(forKey: „engS”) == nil {
// the value has not been set yet, assign a default value
}
I’ve also noticed in your code that you used value(forKey:) - you should not do that on UserDefaults - this is an excellent answer as to why - What is the difference between object(forKey:) and value(forKey:) in UserDefaults?.
On a side note, if you are using a class from iOS SDK for the first time, I highly recommend looking through its docs - they are well written and will provide you with general understanding as to what is possible.
I would recommend you to store this kind of data as a static field in some object to be able to read it from any place. e.g.
class AppController{
static var userDefaults = UserDefaults.standard
}
and then you can save it in your SetConvViewController like
#IBAction func switchEng(_ sender: UISwitch) {
AppController.userDefaults.set(sender.isOn, forKey: engS)
}
and after that you can just read it from any other view controller just by calling
AppController.userDefaults
Using segues you can set to any destination whether it be next vc or previous:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "PreviousVC" {
if let prevVC = segue.destination as? PreviousViewController {
//Your previous vc should have your storage variable.
prevVC.value = self.value
}
}
If you're presenting the view controller:
Destination vc:
//If using storyboard...
let destVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "DestinationViewController") as! DestinationViewController
destVC.value = self.value
self.present(destVC, animated: true, completion: nil)
Previous vc:
weak var prevVC = self.presentingViewController as? PreviousViewController
if let prevVC = prevVC {
prevVC.value = self.value
}
I want to pass data between two view controllers, but don't want the view to change when the users presses my save data button.
The users needs to fill in multiple data fields, and when finish can press another button to go to the second view controller.
I found many tutorials how to pass data using segue, but they all change view as soon as the 'save button is pressed'.
Any one can explain to me how to alter the code?
#Phillip Mills: here is how I used your code. (what am I doing wrong?)
code:
//////// declaring classes on FirstViewController (trying it first on only one ViewController)
class FakeVC1 {
func userInput() {
DataModel.shared.username = outbj14u.text
}
class FakeVC2 {
func viewAppears() {
if let name = DataModel.shared.username {
outbj14p.text = name
print("I have nothing to say")
}
}
}
class DataModel {
static let shared = DataModel()
var username: String?
}
////till here
//// here is where i call the functions
override func viewDidAppear(_ animated: Bool) {
FakeVC1().userInput()
FakeVC2().viewAppears()
if let xbj14p = UserDefaults.standard.object(forKey: "outbj14p") as? String
{
outbj14p.text = xbj14p
}
if let xbj14u = UserDefaults.standard.object(forKey: "outbj14u") as? String
{
outbj14u.text = xbj14u
}
////
#Phillip Mills: Below is what I have know. I think I got the code on the FirstViewController right, but the code on the Second View controller must be wrong. I don't get any errors, but the text field on the SecondViewController remains unchanged after putting input on in the FirstViewController
//// Code on the FirstViewController
class DataModel {
static let shared = DataModel()
var username: String?
}
#IBAction func savebj14p(_ sender: Any) {
outbj14p.text = inbj14p.text
DataModel.shared.username = outbj14p.text
UserDefaults.standard.set(inbj14p.text, forKey: "namebj14p")
}
//and on the SecondViewController
#IBOutlet weak var bj14u: UILabel! // connected to a label
//and
class DataModel {
static let shared = DataModel()
var username: String?
}
override func viewDidAppear(_ animated: Bool) {
if let name = DataModel.shared.username {
bj14u.text = name
}
}
In your case, don't pass data.
Create a shared object to act as your data model. When users fill in the fields, update the data model.
When the user moves to the second controller/view, that controller uses the data model object to show what it needs to.
class FakeVC1 {
func userInput() {
DataModel.shared.username = "Me"
}
}
class FakeVC2 {
func viewAppears() {
if let name = DataModel.shared.username {
print(name)
} else {
print("I have nothing to say")
}
}
}
class DataModel {
static let shared = DataModel()
var username: String?
}
FakeVC1().userInput()
FakeVC2().viewAppears()
If you need to pass value to another viewcontroller without changing the view , you can user NSNotificationCenter class
Refer this link for more details
NSNotificationCenter addObserver in Swift
what i will recommend is to use a global variable or array, you will have the info in all view controllers and you will be able to call it in your new view controller.
This question already has answers here:
Passing data between view controllers
(45 answers)
Closed 5 years ago.
I'm trying to go back to my las viewController with sending data, but it doesn't work.
When I just use popViewController, I can go back to the page, but I can't move my datas from B to A.
Here is my code :
func goToLastViewController() {
let vc = self.navigationController?.viewControllers[4] as! OnaylarimTableViewController
vc.onayCode.userId = taskInfo.userId
vc.onayCode.systemCode = taskInfo.systemCode
self.navigationController?.popToViewController(vc, animated: true)
}
To pass data from Child to parent Controller, you have to pass data using Delegate pattern.
Steps to implement delegation pattern, Suppose A is Parent viewController and B is Child viewController.
Create protocol, and create delegate variable in B
Extend protocol in A
pass reference to B of A when Push or Present viewcontroller
Define delegate Method in A, receive action.
After that, According to your condition you can call delegate method from B.
You should do it using delegate protocol
class MyClass: NSUserNotificationCenterDelegate
The implementation will be like following:
func userDidSomeAction() {
//implementation
}
And ofcourse you have to implement delegete in your parent class like
childView.delegate = self
Check this for more information
https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Protocols.html
You have to send back to last ViewController with 2 options.
1. Unwind segue. (With use of storyboard)
You can refer this link.
2. Use of delegate/protocol.
You can refer this link.
Also this link will be useful for you.
You can use Coordinator Pattern
For example, I have 2 screens. The first displays information about the user, and from there, he goes to the screen for selecting his city. Information about the changed city should be displayed on the first screen.
final class CitiesViewController: UITableViewController {
// MARK: - Output -
var onCitySelected: ((City) -> Void)?
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
onCitySelected?(cities[indexPath.row])
}
...
}
UserEditViewController:
final class UserEditViewController: UIViewController, UpdateableWithUser {
// MARK: - Input -
var user: User? { didSet { updateView() } }
#IBOutlet private weak var userLabel: UILabel?
private func updateView() {
userLabel?.text = "User: \(user?.name ?? ""), \n"
+ "City: \(user?.city?.name ?? "")"
}
}
And Coordinator:
protocol UpdateableWithUser: class {
var user: User? { get set }
}
final class UserEditCoordinator {
// MARK: - Properties
private var user: User { didSet { updateInterfaces() } }
private weak var navigationController: UINavigationController?
// MARK: - Init
init(user: User, navigationController: UINavigationController) {
self.user = user
self.navigationController = navigationController
}
func start() {
showUserEditScreen()
}
// MARK: - Private implementation
private func showUserEditScreen() {
let controller = UIStoryboard.makeUserEditController()
controller.user = user
controller.onSelectCity = { [weak self] in
self?.showCitiesScreen()
}
navigationController?.pushViewController(controller, animated: false)
}
private func showCitiesScreen() {
let controller = UIStoryboard.makeCitiesController()
controller.onCitySelected = { [weak self] city in
self?.user.city = city
_ = self?.navigationController?.popViewController(animated: true)
}
navigationController?.pushViewController(controller, animated: true)
}
private func updateInterfaces() {
navigationController?.viewControllers.forEach {
($0 as? UpdateableWithUser)?.user = user
}
}
}
Then we just need to start coordinator:
coordinator = UserEditCoordinator(user: user, navigationController: navigationController)
coordinator.start()
I was wondering, when passing data using prepareForSegue, can you pass data to a View Controller later in the app? For example on the first ViewController I have the user enter their name. It's not until the very end, so a few views later, do I need to display their name. Is there a way to pass their name without having to go to the end view right away?
Use a Coordinator.
It's really easy to decouple your ViewControllers:
instead of using segues give every ViewController a delegate
create a coordinator object (this object knows your screen flow, not your screens)
the coordinator creates the ViewControllers (it can use UIStoryboard instantiateViewController(withIdentifier:) so ViewController A does not have to know that ViewController B exists
instead of calling performSegue you just call your delegate and pass in the data
Benefits
Simple to use
Easy to reorder screens in a flow
Highly decoupled (easier testing)
Very nice for A/B testing
Scales a lot (you can have multiple coordinators, one for each flow)
Sample
Let's say you have 3 VCs, the first one asks for your name, the second for your age and the third displays the data. It would make no sense that AgeViewController knew that NameViewController existed, later on you may want to change their order or even merge them.
Name View Controller
protocol NameViewControllerDelegate: class {
func didInput(name: String)
}
class NameViewController: UIViewController {
weak var delegate: NameViewControllerDelegate?
#IBOutlet var nameTextField: UITextField!
//Unimportant stuff ommited
#IBAction func submitName(sender: Any) {
guard let name = nameTextField.text else {
// Do something, it's up to you what
return
}
delegate?.didInput(name: name)
}
}
Age View Controller
protocol AgeViewControllerDelegate: class {
func didInput(age: Int)
}
class AgeViewController: UIViewController {
weak var delegate: AgeViewControllerDelegate?
#IBOutlet var ageTextField: UITextField!
//Unimportant stuff ommited
#IBAction func submitAge(sender: Any) {
guard let ageString = ageTextField.text,
let age = Int(ageString) else {
// Do something, it's up to you what
return
}
delegate?.didInput(age: age)
}
}
Displayer View Controller
class DisplayerViewController: UIViewController {
var age: Int?
var name: String?
}
Coordinator
class Coordinator {
var age: Int?
var name: String?
var navigationController: UINavigationController
init(navigationController: UINavigationController) {
self.navigationController = navigationController
}
fileprivate lazy var storyboard: UIStoryboard = {
return UIStoryboard(name: "MyStoryboard", bundle: nil)
}()
//This works if you name your screns after their classes
fileprivate func viewController<T: UIViewController>(withType type: T.Type) -> T {
return storyboard.instantiateViewController(withIdentifier: String(describing: type(of: type))) as! T
}
func start() -> UIViewController {
let viewController = self.viewController(withType: NameViewController.self)
viewController.delegate = self
navigationController.viewControllers = [viewController]
return viewController
}
}
Coordinator + Name View Controller Delegate
extension Coordinator: NameViewControllerDelegate {
func didInput(name: String){
self.name = name
let viewController = self.viewController(withType: AgeViewController.self)
viewController.delegate = self
navigationController.pushViewController(viewController, animated: true)
}
}
Coordinator + Age View Controller Delegate
extension Coordinator: AgeViewControllerDelegate {
func didInput(age: Int) {
self.age = age
let viewController = self.viewController(withType: DisplayerViewController.self)
viewController.age = age
viewController.name = name
navigationController.pushViewController(viewController, animated: true)
}
}
Not really. You can pass view by view the item but it's not a proper way of doing things.
I suggest you to have a Static Manager or this kind of stuff to store the information globally in your app to retrieve it later
All the solution are pretty good. Possible you can try the below model also
1. DataModel class
1.1 Should be singleton class
1.2 Declare value
Step 1 : ViewCOntroller-one
1 Create the Sharedinstance of singleton class
1.1 Assign the value
Step 3 :ViewController-two
1 Create the Sharedinstance of singleton class
1.1 Get the value