I have custom init method for my UIViewController, I want to load it from storyBoard as only XYZController() gives blank View.
convenience init() {
self.init(imageURL: nil)
}
init(imageURL: NSURL?){
//code to load the ViewController from StoryBoard
super.init(nibName: nil, bundle: NSBundle.mainBundle())
}
required init(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)!
}
If you want to load the view controller from the storyboard, then you're going to have to follow a slightly different pattern.
First, name the segue to your view controller in the storyboard (click on it, then enter a name for 'Identifier' in the properties tab.
When the segue is triggered, prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) will be called. You can make sure you're moving to the appropriate view controller by checking the segue's identifier property, then cast the segue's destinationViewController to you XYZViewController.
After that, you should be able to call a setup function or however you want to supply the image url to the controller.
I'm having issue for writing custom init for subclass of UIViewController, basically I want to pass the dependency through the init method for viewController rather than setting property directly like viewControllerB.property = value
So I made a custom init for my viewController and call super designated init
init(meme: Meme?) {
self.meme = meme
super.init(nibName: nil, bundle: nil)
}
The view controller interface resides in storyboard, I've also make the interface for custom class to be my view controller. And Swift requires to call this init method even if you are not doing anything within this method. Otherwise the compiler will complain...
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
The problem is when I try to call my custom init with MyViewController(meme: meme) it doesn't init properties in my viewController at all...
I was trying to debug, I found in my viewController, init(coder aDecoder: NSCoder) get called first, then my custom init get called later. However these two init method return different self memory addresses.
I'm suspecting something wrong with the init for my viewController, and it will always return self with the init?(coder aDecoder: NSCoder), which, has no implementation.
Does anyone know how to make custom init for your viewController correctly ?
Note: my viewController's interface is set up in storyboard
here is my viewController code:
class MemeDetailVC : UIViewController {
var meme : Meme!
#IBOutlet weak var editedImage: UIImageView!
// TODO: incorrect init
init(meme: Meme?) {
self.meme = meme
super.init(nibName: nil, bundle: nil)
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override func viewDidLoad() {
/// setup nav title
title = "Detail Meme"
super.viewDidLoad()
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
editedImage = UIImageView(image: meme.editedImage)
}
}
As it was specified in one of the answers above you can not use both and custom init method and storyboard.
But you still can use a static method to instantiate ViewController from a storyboard and perform additional setup on it.
It will look like this:
class MemeDetailVC : UIViewController {
var meme : Meme!
static func makeMemeDetailVC(meme: Meme) -> MemeDetailVC {
let newViewController = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "IdentifierOfYouViewController") as! MemeDetailVC
newViewController.meme = meme
return newViewController
}
}
Don't forget to specify IdentifierOfYouViewController as view controller identifier in your storyboard. You may also need to change the name of the storyboard in the code above.
You can't use a custom initializer when you initialize from a Storyboard, using init?(coder aDecoder: NSCoder) is how Apple designed the storyboard to initialize a controller. However, there are ways to send data to a UIViewController.
Your view controller's name has detail in it, so I suppose that you get there from a different controller. In this case you can use the prepareForSegue method to send data to the detail (This is Swift 3):
override func prepare(for segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "identifier" {
if let controller = segue.destinationViewController as? MemeDetailVC {
controller.meme = "Meme"
}
}
}
I just used a property of type String instead of Meme for testing purposes. Also, make sure that you pass in the correct segue identifier ("identifier" was just a placeholder).
As #Caleb Kleveter has pointed out, we can't use a custom initializer while initialising from a Storyboard.
But, we can solve the problem by using factory/class method which instantiate view controller object from Storyboard and return view controller object.
I think this is a pretty cool way.
Note: This is not an exact answer to question rather a workaround to solve the problem.
Make class method, in MemeDetailVC class, as follows:
// Considering your view controller resides in Main.storyboard and it's identifier is set to "MemeDetailVC"
class func `init`(meme: Meme) -> MemeDetailVC? {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let vc = storyboard.instantiateViewController(withIdentifier: "MemeDetailVC") as? MemeDetailVC
vc?.meme = meme
return vc
}
Usage:
let memeDetailVC = MemeDetailVC.init(meme: Meme())
One way that I've done this is with a convenience initializer.
class MemeDetailVC : UIViewController {
convenience init(meme: Meme) {
self.init()
self.meme = meme
}
}
Then you initialize your MemeDetailVC with let memeDetailVC = MemeDetailVC(theMeme)
Apple's documentation on initializers is pretty good, but my personal favorite is the Ray Wenderlich: Initialization in Depth tutorial series which should give you plenty of explanation/examples on your various init options and the "proper" way to do things.
EDIT: While you can use a convenience initializer on custom view controllers, everyone is correct in stating that you cannot use custom initializers when initializing from the storyboard or through a storyboard segue.
If your interface is set up in the storyboard and you're creating the controller completely programmatically, then a convenience initializer is probably the easiest way to do what you're trying to do since you don't have to deal with the required init with the NSCoder (which I still don't really understand).
If you're getting your view controller via the storyboard though, then you will need to follow #Caleb Kleveter's answer and cast the view controller into your desired subclass then set the property manually.
There were originally a couple of answers, which were cow voted and deleted even though they were basically correct. The answer is, you can't.
When working from a storyboard definition your view controller instances are all archived. So, to init them it's required that init?(coder... be used. The coder is where all the settings / view information comes from.
So, in this case, it's not possible to also call some other init function with a custom parameter. It should either be set as a property when preparing the segue, or you could ditch segues and load the instances directly from the storyboard and configure them (basically a factory pattern using a storyboard).
In all cases you use the SDK required init function and pass additional parameters afterwards.
Swift 5
You can write custom initializer like this ->
class MyFooClass: UIViewController {
var foo: Foo?
init(with foo: Foo) {
self.foo = foo
super.init(nibName: nil, bundle: nil)
}
public required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
self.foo = nil
}
}
UIViewController class conform to NSCoding protocol which is defined as:
public protocol NSCoding {
public func encode(with aCoder: NSCoder)
public init?(coder aDecoder: NSCoder) // NS_DESIGNATED_INITIALIZER
}
So UIViewController has two designated initializer init?(coder aDecoder: NSCoder) and init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?).
Storyborad calls init?(coder aDecoder: NSCoder) directly to init UIViewController and UIView,There is no room for you to pass parameters.
One cumbersome workaround is to use an temporary cache:
class TempCache{
static let sharedInstance = TempCache()
var meme: Meme?
}
TempCache.sharedInstance.meme = meme // call this before init your ViewController
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder);
self.meme = TempCache.sharedInstance.meme
}
As of iOS 13 you can initialize the view controller that resides in a storyboard using:
instantiateViewController(identifier:creator:) method on the UIStoryboard instance.
tutorial:
https://sarunw.com/posts/better-dependency-injection-for-storyboards-in-ios13/
Although we can now do custom init for the default controllers in the storyboard using instantiateInitialViewController(creator:) and for segues including relationship and show.
This capability was added in Xcode 11 and the following is an excerpt from the Xcode 11 Release Notes:
A view controller method annotated with the new #IBSegueAction attribute can be used to create a segue’s destination view controller in code, using a custom initializer with any required values. This makes it possible to use view controllers with non-optional initialization requirements in storyboards. Create a connection from a segue to an #IBSegueAction method on its source view controller. On new OS versions that support Segue Actions, that method will be called and the value it returns will be the destinationViewController of the segue object passed to prepareForSegue:sender:. Multiple #IBSegueAction methods may be defined on a single source view controller, which can alleviate the need to check segue identifier strings in prepareForSegue:sender:. (47091566)
An IBSegueAction method takes up to three parameters: a coder, the sender, and the segue’s identifier. The first parameter is required, and the other parameters can be omitted from your method’s signature if desired. The NSCoder must be passed through to the destination view controller’s initializer, to ensure it’s customized with values configured in storyboard. The method returns a view controller that matches the destination controller type defined in the storyboard, or nil to cause a destination controller to be initialized with the standard init(coder:) method. If you know you don’t need to return nil, the return type can be non-optional.
In Swift, add the #IBSegueAction attribute:
#IBSegueAction
func makeDogController(coder: NSCoder, sender: Any?, segueIdentifier: String?) -> ViewController? {
PetController(
coder: coder,
petName: self.selectedPetName, type: .dog
)
}
In Objective-C, add IBSegueAction in front of the return type:
- (IBSegueAction ViewController *)makeDogController:(NSCoder *)coder
sender:(id)sender
segueIdentifier:(NSString *)segueIdentifier
{
return [PetController initWithCoder:coder
petName:self.selectedPetName
type:#"dog"];
}
In XCode 11/iOS13, you can use
instantiateViewController(identifier:creator:)
also without segues:
let vc = UIStoryboard(name: "StoryBoardName", bundle: nil).instantiateViewController(identifier: "YourViewControllerIdentifier", creator: {
(coder) -> YourViewController? in
return YourViewController(coder: coder, customParameter: "whatever")
})
present(vc, animated: true, completion: nil)
Disclaimer: I do not advocate for this and have not thoroughly tested its resilience, but it is a potential solution I discovered while playing around.
Technically, custom initialization can be achieved while preserving the storyboard-configured interface by initializing the view controller twice: the first time via your custom init, and the second time inside loadView() where you take the view from storyboard.
final class CustomViewController: UIViewController {
#IBOutlet private weak var label: UILabel!
#IBOutlet private weak var textField: UITextField!
private let foo: Foo!
init(someParameter: Foo) {
self.foo = someParameter
super.init(nibName: nil, bundle: nil)
}
override func loadView() {
//Only proceed if we are not the storyboard instance
guard self.nibName == nil else { return super.loadView() }
//Initialize from storyboard
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let storyboardInstance = storyboard.instantiateViewController(withIdentifier: "CustomVC") as! CustomViewController
//Remove view from storyboard instance before assigning to us
let storyboardView = storyboardInstance.view
storyboardInstance.view.removeFromSuperview()
storyboardInstance.view = nil
self.view = storyboardView
//Receive outlet references from storyboard instance
self.label = storyboardInstance.label
self.textField = storyboardInstance.textField
}
required init?(coder: NSCoder) {
//Must set all properties intended for custom init to nil here (or make them `var`s)
self.foo = nil
//Storyboard initialization requires the super implementation
super.init(coder: coder)
}
}
Now elsewhere in your app you can call your custom initializer like CustomViewController(someParameter: foo) and still receive the view configuration from storyboard.
I don't consider this a great solution for several reasons:
Object initialization is duplicated, including any pre-init properties
Parameters passed to the custom init must be stored as optional properties
Adds boilerplate which must be maintained as outlets/properties are changed
Perhaps you can accept these tradeoffs, but use at your own risk.
Correct flow is, call the designated initializer which in this case is the init with nibName,
init(tap: UITapGestureRecognizer)
{
// Initialise the variables here
// Call the designated init of ViewController
super.init(nibName: nil, bundle: nil)
// Call your Viewcontroller custom methods here
}
This solution shows a way to have custom initializers but still be able to use Storyboard WITHOUT using the self.init(nib: nil, bundle: nil) function.
To make it possible to use that, let’s first tweak our MemeDetailsVC to also accept an NSCoder instance as part of its custom initializer, and to then delegate that initializer to super.init(coder:), rather than its nibName equivalent:
class MemeDetailVC : UIViewController {
var meme : Meme!
#IBOutlet weak var editedImage: UIImageView!
init?(meme: Meme, coder: NSCoder) {
self.meme = meme
super.init(coder: aDecoder)
}
#available(*, unavailable, renamed: "init(product:coder:)")
required init?(coder: NSCoder) {
fatalError("Invalid way of decoding this class")
}
override func viewDidLoad() {
title = "Detail Meme"
super.viewDidLoad()
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
editedImage = UIImageView(image: meme.editedImage)
}
}
And then, you instantiate & show the View Controller this way:
guard let viewController = storyboard?.instantiateViewController(
identifier: "MemeDetailVC",
creator: { coder in
MemeDetailVC(meme: meme, coder: coder)
}
) else {
fatalError("Failed to create Product Details VC")
}
//Then you do what you want with the view controller.
present(viewController, sender: self)
// View controller is in Main.storyboard and it has identifier set
Class B
class func customInit(carType:String) -> BViewController
{
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let objClassB = storyboard.instantiateViewController(withIdentifier: "BViewController") as? BViewController
print(carType)
return objClassB!
}
Class A
let objB = customInit(carType:"Any String")
navigationController?.pushViewController(objB,animated: true)
So here's my situation. I am using SWRevealViewController and on the rear VC I have some UI elements that need to be updated when a notification comes through. My problem is that the view may not be visible (and thus isn't loaded) when the notification comes through, so obviously the view hasn't had a chance to register its observers. As a workaround, I tried to instantiate the view controller in my AppDelegate before I post the notification, and originally when I tried this, the IBOutlets were nil. Then I found another question (here) that suggested using the initWithCoder method since this is called when the View Controller is instantiated from the storyboard. However, even using this practice my IBOutlets are still nil. Is there a way to accomplish what I'm trying to do here, or not?
AppDelegate Code (in application:didReceiveRemoteNotification):
let storyboard = UIStoryabord(name: "Main", bundle: nil)
let menuVC = storyboard.instantiaveViewControllerWithIdentifier("menuVC")
NSNotificationCenter.defaultCenter.addObserver(menuVC, selector: "updateMessagesBadge:", name: "notificationName", object: nil)
NSNotificationCenter.defaultCenter.postNotification("notificationName", object: nil)
MenuVC Code:
required init?(coder: aDecoder: NSCoder) {
super.init(coder: aDecoder)
//what to do here?
}
func updateMessagesBadge(notification: NSNotification) {
//try to change outlet properties, but outlets are nil
}
I am building in iOS 9 with Swift 2.0. I have my starting UIViewController that is my menu screen. It contains the following code:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if let id = segue.identifier where id == "GamePlayScene" {
self.gameVC = segue.destinationViewController as? GameViewController
self.gameVC!.delegate = self
if let s = sender as? GKTurnBasedMatch {
self.gameVC!.match = s
}
}
}
When segueing to my GameViewController, the following init runs before that prepareForSegue even gets called:
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
GKLocalPlayer.localPlayer().registerListener(self) // I only want this once
}
In storyboard, my GameViewController has a "Menu" button that is connected to the exit widget for the view controller and it unwinds to the Menu as intended. But whenever I perform the segue again, the init gets called again so I now have multiple GameViewControllers. I think this slows my app down since I am using SKScenes. How do I perform a segue without it creating a new object every time?
func player(player: GKPlayer, receivedTurnEventForMatch match: GKTurnBasedMatch, didBecomeActive: Bool) {
if didBecomeActive {
// This event is what activated the app, so the user wants it right meow
GameKitHelper.sharedInstance.match = match
performSegueWithIdentifier("GamePlayScene", sender: match)
}
}
You can store your GameViewController in a singleton so that it only needs to be created once. Since the view controller is initialized only once it saves processing time. This is probably a good performance optimization for an app using two view controllers, such as your game, that need to frequently be switched back and forth between the two.
The way to do this is to create a new Swift class and have it accessible as a shared instance where the second view controller is stored in a private property. The second view controller is instantiated if it has not yet been initialized. Further retrievals of the view controller return the stored view controller thereby eliminating the need to initialize the view controller. The operations for creating the view controller, storing it, and returning it are handled by the getter of a publically accessible computed property.
Here is the code for the class:
Singleton.swift:
import Foundation
import UIKit
class Singleton {
static let sharedInstance = Singleton()
var gameViewController: GameViewController {
get {
if self.storedViewController == nil {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
self.storedViewController =
storyboard.instantiateViewControllerWithIdentifier("GameViewController") as? GameViewController
}
return self.storedViewController!
}
}
private var storedViewController: GameViewController?
}
To use this, it will be necessary to use the showViewController method of showing the game view controller instead of using a segue.
In the first view controller I have:
#IBAction func buttonWasPressed(sender: AnyObject) {
let vc = Singleton.sharedInstance.gameViewController
navigationController?.showViewController(vc, sender: self)
}
The second controller (GameViewController) will now only be created once and re-used every time the button is pressed on the first view controller.
GKLocalPlayer.localPlayer().registerListener(self) // I only want this once
The way to cause a line of code to run only once over the lifetime of the app is with dispatch_once.
So I created a delegate in the following way:
class MessengerTableViewController: UITableViewController, MessengerTableViewControllerDelegate, UITableViewDataSource, UITextFieldDelegate {
//..Insert Various functions Here..
func messengerScrollToBottom() {
self.tableView.setContentOffset(CGPointMake(0, CGFLOAT_MAX), animated: true)
}
}
The protocol is :
protocol MessengerTableViewControllerDelegate {
func messengerScrollToBottom()
}
And the class using messengerScrollToBottom() is the superView :
class ContainerViewController: UIViewController, UITextFieldDelegate {
#IBOutlet var containerViewController : UIView
init(coder aDecoder: NSCoder!) {
super.init(coder: aDecoder)
self.msgDelegate = MessengerTableViewController(coder: nil)
}
func keyboardWillShow(aNotification: NSNotification) {
self.msgDelegate!.messengerScrollToBottom()
}
}
This will not work because within the ContainerViewController init() function, msgDelegate is not assigned to the proper MessageTableViewController. It does not point to the MessengerTableViewController that is already created by the storyboard in memory. Therefore the code executes fine, however I see no change in the tableView onscreen. My question is, how can I modify this code to have it occur as intended?
Here is an image of my storyboard:
http://imgur.com/z09dapF
Help would be appreciated!
EDIT:
override func prepareForSegue(segue: UIStoryboardSegue?, sender: AnyObject?) {
// Get the new view controller using [segue destinationViewController ].
if segue?.identifier == "tableView" {
let child = segue!.destinationViewController as? MessengerTableViewController
self.msgDelegate = child
}
// Pass the selected object to the new view controller.
}
I implemented the code above and now it works..except with one catch. The tableView is blank upon executing messengerScrollToBottom() . Any know why?
Second edit: Turns out CGFLOAT_MAX was the problem, thanks.
You need to set the delegate when you segue to the MessengerTableViewController. Since you're using a segue, you should do that in prepareForSegue. Get a reference to the MessengerTableViewController with segue.destinationViewController.
override func prepareForSegue(segue: UIStoryboardSegue!, sender: AnyObject!) {
let messengerTVC: MessengerTableViewController = segue.destinationViewController as ViewController
self.msgDelegate = messengerTVC;
}
Maybe try declaring a MessageTableViewController property in your header file, and then bind it to the MessageTableViewController in your storyboard? Then in the init() you could assign that property to be the object's delegate?