I have 3 classes :
Core that doesn't inherit from any class.
vcMain and vcIncomingFile which both inherit from UIViewController.
I have a segue from vcMain to vcIncomingFile.
How can I call the -performSegueWithIdentifier: method from the Core class,between vcMain and vcIncoming. I mean I want to have a method or delegate or anything else in Core class that can performSegue from vcMain to vcIncomingFile.
class Core {
func showIncomingVC(){ }
}
in showIncomingVC function, I want to performSegue between vcMain and vcIncomingFile.
Thanks
To implement the patterns properly we would need to know if your Core class is part of your model or if it is some kind of control flow mechanism.
If it is part of the model, it should know nothing about the view controllers but the view controllers are allowed to access it. In this case your view controllers could implement a delegate protocol of some sort and establish a call path from your Core class by assigning themselves as a delegate for some part of the Core functionality. The Core could then trigger any pre-defined behaviour in its delegates by calling the methods defined in the protocol.
For example,
If you define a protocol called FileEventDelegate with a method named fileReceived().
Then, add a member to your Core class called fileEventDelegate of type FileEventDelegate?
Whenever the Core class receives a file, it can call fileEventDelegate?.fileReceived(). The object instance, of whichever class implements the protocol, that registered itself as the delegate will handle it from there.
A unit testing class could also be the delegate and not even have nor need a segue to be performed.
Your Core class could even work without a delegate being set.
On the UI side, your VcMain class can implement the FileEventDelegate protocol by defining a fileReceived() function that call performSegueWithIdentifier(...). On viewLoaded() it can set itself as the fileEventDelegate of the Core class instance it is working with.
This keeps all model-to-visual logic in the viewController where it belongs.
If your Core class works in complete separation of the view controllers (meaning that the view controllers don't know how to access the instance(s) of Core), you may want to look into NSNotificationCenter and send notifications out in the universe for your viewControllers to pick-up asynchronously.
Core needs to be of UIViewController or some class that inherit UIViewController because performSegueWithIdentifier is a function of UIViewController
https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIViewController_Class/index.html#//apple_ref/occ/instm/UIViewController/performSegueWithIdentifier:sender:
You can work with protocol instead. Create a protocol in your Core class with func showIncomingVC(){ } and use its delegate in your view class
Just do like this:
struct Segue {
let sourceVC: UIViewController
let sender: AnyObject
let identifier: String
}
protocol SegueProtocol: class {
var segue: Segue { get }
}
class Core {
weak var delegate: SegueProtocol?
func perform() {
guard let segue = delegate?.segue else {
return
}
segue.sourceVC.performSegueWithIdentifier(segue.identifier, sender: segue.sender)
}
}
Related
I'm new to Swift and I'm sure this question is pretty basic and has been asked and answered before.
I am not using storyBoard. My main viewController is created from AppDelegate via code.
I have:
a custom class defined in a model.swift file
a main viewController (from AppDelegate) that I am using as a container
3 additional viewcontrollers as subviews of the main (not each other)
all 3 subviews are displayed simultaneously each covering 1/3 of the screen (no segues)
each viewcontroller is in a separate .swift file
I want to create an instance of my custom class in the main viewController and have all 3 of the subviews be able to reference that instance.
Each of the subview view controllers need to be able to get/set instance variables and the other subviews need to be made aware of those changes.
I think I will need to use notifications to communicate the changes to the multiple subviews - but I haven't even begun to try and figure that out yet.
If this has been asked and answered before - could someone please either provide a link - or provide me with the right search terms so that I'm able to find the answer? The only found answers I've found that come close are to use segues to pass the data back and forth.
You can use delegate pattern. Below code is assuming that you are using MVVM pattern. (It is very similar for VIPER/ReSwift patterns also)
protocol DataChangedDelegate {
func refreshData()
}
// ViewModel for FirstViewController
class FirstViewModel {
var delegate: DataChangedDelegate?
var data: Any {
didSet {
delegate?.refreshData()
}
}
//rest of the things
}
//similarly other two view models will have a delegate and on data change will call the refresh method
And your view controllers should adopt this protocol
class FirstViewController: UIViewController, DataChangedDelegate {
//view controller code
//delegate code
func refreshDate() {
//tableView.reloadDate()
//collectionView.reloadDate()
//lableView.text = viewModel.data()
}
}
And where ever you create a viewControllers and add as subView, you have to set the delegate of viewModel.
let firstViewController: FirstViewController = createFirstViewController()
let firstViewModel = FirstViewModel()
firstViewModel.delegate = firstViewController
firstViewController.viewModel = firstViewModel
mainViewController.addSubView(firstViewController.view)
Similarly for all other view controllers.
Here's how I would do it:
Create a singleton class.
Configure the singleton's properties in the the main ViewController.
Use didSet to post a Notification.
Add a listener for that Notification in your additional ViewControllers.
View Controller A has access to a model and can mutate the model. View Controller B displays the model. I want when View Controller A updates the model, a method to be triggered in View Controller B such that the view is updated. Is there a standard way to do this in Swift?
In the didset of this variable you can post a notification and the other controller can register for this notification. (We can do it more neatly depending on the requirement.)
If you make your model object an Objective-C object (#objc) then you can use KVO (key-value observering) to observe changes to it. If you do that then any object that's observing a property of the model will get notified when that property changes.
Here is one way you could do this.
Have whatever model you use, class or struct, implement a protocol that can be be used by view-controller B. view-controller B should not care what the model is, only that it conforms to the protocol it needs to extract the data it needs.
When view-controller A manipulates the model, post a notification with a reference to the model as an instance of the protocol, in the userInfo dictionary. view-controller B, subscribes to the notification and when triggered, extracts the reference from the userInfo and then gets the data it needs via the common protocol.
Another way to communicate between 2 view controllers is Protocol. Define a protocol, such as:
protocol ViewControllerAModelProtocol: class {
func viewControllerAModelDidUpdate()
}
In ViewControllerA, define a delegate type:
weak var updatedProtocol: viewControllerAModelDidUpdate?
When the model is updated and call:
updatedProtocol?.viewControllerAModelDidUpdate()
In ViewControllerB, implement the protocol:
class ViewControllerB: UIViewController, ViewControllerAModelProtocol {
func viewControllerAModelDidUpdate() {
// reloadData()
}
}
If ViewControllerB is presented or showed by ViewControllerA, set A's updatedProtocol to B:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let b = segue.destination as? ViewControllerAModelProtocol {
self.updatedProtocol = b
}
}
I'm learning Swift and I'm studying the delegation pattern.
I think I understand exactly what is delegation and how it works, but I have a question.
I have a situation where Controller A is the delegate for Controller B.
In controller B I define a delegate protocol.
In controller B I set a variable delegate (optional)
In controller B I send message when something happens to the delegate
Controller A must adopt method of my protocol to become a delegate
I cannot understand if every delegate controller (in this case A) listens for messages sent by controller B or If I have to tell to controller B that A is now his delegate.
I notice that someone use this code (in controller A)
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "Example" {
let navigationController = segue.destinationViewController as UINavigationController
let controller = navigationController.topViewController as AddItemViewController
controller.delegate = self
}
}
Is this the only way to tell a delegator who is his delegate?
I believe, you need to tell a deligator who is its delegate upon creation of that it. Now, the delegator can be created programatically or through storyboard. So, based on that you have two options, you can tell it who is its delegator programatically like you showed in the code or from IB.
The key here is upon creation. Let's me explain myself. Take the case of a UIView. Say, you want a Custom UIView object(CustomView). So, you drag and drop a UIView in your View Controller and in the identity inspector, you assign its class as of your CustomView's class. So, basically, as soon as the controller is created, your custom view will also be created. Now, you can either say it that the View Controller in which it is created is its delegate or You can go to the IB and connect the view's delegate to the View Controller.
Now, let's assume that you wanted the custom view to be created in your ViewController programatically. In that case, you would probably call the -initWithFrame: method to create the view and upon creation you tell that delegator that who is its delegate like-
myCustomView.delegate = self;
same goes with a View Controller.
controller.delegate = self;
So, basically to tell a delegator who is its delegate, you first need that delegator to be created. At least, that's what I think.
I think one of the best example of delegation is UITableView.
Whenever you want the control of various properties of a tableView e.g. rowHeight etc, you set your controller to be the delegate of your tableview. To set the delegate of your tableView you need to have tableView created obviously as pointed out by #natasha.
So in your case, you can set delegate of your delegator when you create it or when you find a need for the controller to be delegate of your delegator but you definitely need your delegator to be present to set its property.
You can set your controller as delegate at any time when you require control.
I'm sure you want your UIViewController to act like described, but here is a simpler example how to use the delegation pattern with custom classes:
protocol ControllerBDelegate: class {
func somethingHappendInControllerB(value: String)
/* not optional here and passes a value from B to A*/
/* forces you to implement the function */
}
class ControllerB {
var delegate: ControllerBDelegate?
private func someFunctionThatDoSomethingWhenThisControllerIsAlive() {
/* did some magic here and now I want to tell it to my delegate */
self.delegate?.somethingHappendInControllerB(value: "hey there, I'm a magician")
}
func doSomething() {
/* do something here */
self.someFunctionThatDoSomethingWhenThisControllerIsAlive()
/* call the function so the magic can really happen in this example */
}
}
class ControllerA: ControllerBDelegate {
let controllerB = ControllerB()
init() {
self.controllerB.delegate = self /* lets say we add here our delegate*/
self.controllerB.doSomething() /* tell your controller B to do something */
}
func somethingHappendInControllerB(value: String) {
print(value) /* should print "hey there, I'm a magician" */
}
}
I wrote the code from my mind and not testet it yet, but you should get the idea how to use such a pattern.
I have an UITableView that is loaded from two custom cell xib files.
The second one contains an UIButton.
But since i've added the custom class for xib - it has its own actions and functions, which i cannot access from ViewController.
My goal is to apply some action on UIButton when the custom cell is loaded in the tableview.
My function is defined in ViewController (because all variables are there) and my UIButton action is defined in Custom class for xib.
How do i connect one to another?
Thank you
Here is the solution in swift
If you want to perform action in another class when an event takes place in another class, then you have to use Protocols in your code, so that you can perform the action in another class.
For example
Declare your protocol like this before the class interface
protocol MyDelegateClass {
func btnAction()
}
Define your protocol in the interface of your class like this
var MyDelegateClass! = nil
Now on your button action trigger the protocol like this
#IBAction func btnProtocolAction(sender: AnyObject) {
[delegate btnAction];
}
Now include the protocol in the class like this
class myActionClass: UIViewController, PopUpViewDelegate {
Now assign the protocol to the MyDelegateClass object like this
myProtocolObject.delegate=self
Also define the class which you have declared in MyDelegateClass like
func btnAction() {
print(#"This method will triggered");
}
Hope this helps you.
You can achieve this by simply posting a notification.
NSNotificationCenter.defaultCenter().postNotificationName("buttonClickedNotification", object: nil)
Post this notification from your button method in custom class. You can also pass any data by using object parameter (Here it is nil).
And observe the notification in your viewController.
NSNotificationCenter.defaultCenter().addObserver(self, selector: "buttonClicked:", name: "buttonClickedNotification", object: nil)
And implement buttonClicked() method in your viewController.
func buttonClicked(data: NSNotification)
{
//If any data is passed get it using
let receivedData:NSDictionary = data.object as! NSDictionary //If data is of NSDictionary type.
}
Write a delegate method. This will connect your ViewController and Custom Class. What have you tried already?
I am creating an ios app with swift. I have an UIViewController and an "UserManager" class which inherits from NSObject. Basically, when the user opens the app, the code within UIViewController is executed. UIViewController calls a function in UserManager. When this function has finished, I want that a segue be performed (a segue called "connectSegue" in my code). I am a beginner...
What I have done (and didn't work!) :
Here is my ViewController :
import UIKit
var profileUser = UserManager()
class ViewController : UIViewController{
override func viewDidLoad() {login()}
func login()->Void {profileUser.createUser()}
func handleSegue()->Void {self.performSegueWithIdentifier("connectSegue",sender: self)}
}
Here is my UserManager class :
import Foundation
class UserManager: NSObject {
//Some properties
func createUser()->Void {
//Some code
var segueHandler = ViewController()
segueHandler.handleSegue()
}
}
How can I do that?
Thank you
The problem is that your UserManager is creating a new instance of ViewController, which is not the one that called UserManager.
A better way to handle this is to call performSegueWithIdentifier in your ViewController, after calling login.
In general, you are better off not putting UI navigation inside non-UI classes. UserManager will be more useful if it does user functions only, not UI responsibilities. If UserManager is doing its work asynchronously, then you should consider using notifications to communicate back to your ViewController when the work is complete so it can perform the segue.