I'm, relatively, a beginner, so this may be an entirely common practice—or an entirely impossible one—but I've been wondering if it's possible to modify a view controller added in a storyboard so that instead of (or in addition to?) being an instance of UIViewConroller, it's also an instance of (blahblah)ViewController, e.g. ABUnknownPersonViewController.
That way, instead of doing something like this:
class ViewController : UIViewController {
override func viewDidLoad() {
let test = ABUnknownPersonViewController()
...
self.presentViewController(test, animated: false, completion: nil)
}
}
This could be done:
class ViewController : ABUnknownPersonViewController {
override func viewDidLoad() {
//ViewController already is an ABUnknownPersonViewController, so you can treat it as one
//example below (displayedPerson is a property of ABUnkownPersonViewControllers)
self.displayedPerson...
}
}
EDIT: ABUnknownPersonViewController is a class supplied by Apple, which does not support subclassing (here). With that said, and the understanding that I would obviously like as simple a solution as possible (avoidance of protocols and whatnot), what are my options?
I tried class FourthViewController: UIViewController, ABUnknownPersonViewController, ABUnknownPersonViewController, ABUnknownPersonViewControllerDelegate only to get an error about multiple inheritance.
It sounds like what you actually want to do is to subclass UIViewController, and in your storyboard, set the custom class to your subclass. When the view controller is loaded from the storyboard, it will be an instance of your subclass.
So your subclass would look like this:
class ABUnknownPersonViewController : UIViewController {
override func viewDidLoad() {
self.displayedPerson...
}
}
In the storyboard, highlight the view controller you want to use a custom class for, and in the Custom Class field, type the name of your subclass. If you've done it correctly, it should autocomplete for you.
Related
I have a storyboard, and it needs to be used in few places. Is there any other option than just duplicate storyboard and assign it to new view controller? I want to avoid boilerplate code and writing 3x same outlets and others. I need exactly same layout and almost all functions in all three controllers, but I want to only change model for all of them.
I have tried to do it like this:
class FirstViewController: UIViewController {
//outlets
// code
// tableView configuration
}
class SecondViewController: FirstViewController {
// and here I have just overrided some function to modify them
}
I have two main screens in my app, currently both just subclasses of UIViewController. These two view controllers are very similar - they both implement my custom subclass of UIView called HeaderView that is responsible for displaying information and taking user input. As it stands, this code is repetitive because the HeaderView setup is the same for both view controllers - the only difference is what happens when the user confirms the text entry in HeaderView.
To cut down on repetitive code, I am creating a class called InputViewController (a subclass of UIViewController) that houses the aspects of the two view controllers that are identical. Eventually, I want the two view controllers to subclass InputViewController instead of UIViewController.
class InputViewController: UIViewController, InputProtocol {
private let headerView = HeaderView()
override func viewDidLoad() {
super.viewDidLoad()
// layout, etc.
setupCallbacks()
}
internal func setupCallbacks() {
headerView.onUpdate = { (text: String) in
// called when user confirms text entry in headerView
self.onHeaderUpdate()
}
}
internal func onHeaderUpdate() {} // Blank function
}
setupCallbacks() and onHeaderUpdate() are methods defined in the protocol that the InputViewController conforms to. The HeaderView implements a callback closure that is handled in setupCallbacks() by headerView.onUpdate...
The protocol that InputViewController conforms to:
protocol InputProtocol {
func setupCallbacks()
func onHeaderUpdate()
}
To illustrate this, I drew up a diagram;
Since I want the subclasses of InputViewController to override the onHeaderUpdate() method, is it conventional to leave the definition of onHeaderUpdate() in InputViewController blank or is there another solution to this?
is it conventional to leave the definition of onHeaderUpdate() in InputViewController blank
Yes, that is called an abstract method. It is common to give it code that crashes deliberately, as a way of saying, “I exist only to be overridden in a subclass.”
(I should go further and say that what you are creating, a base view controller that carries out initial configurations that all subclasses must implement, is also normal.)
I see this topic is discussed elsewhere but I don't see an answer to my questions.
I subclassed UIView to create a custom view. Currently I'm using interface builder to create a UIView and then setting the custom class option to my subclass.
First question. When I do that, how to I reference that instance from my code? I have a public function I would like to call that updates my view but I don't know how to call it from my view controller
Second question. I created an instance of the class from within my view controller just playing around and I noticed the public function I created isn't available with that instance. Can I create public functions when I inherit from UIView?
It is easy to do:
1)subclass UIView to create CustomView, add your public function,in your project:
import UIKit
class CunstomView: UIView {
/*
// Only override draw() if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
override func draw(_ rect: CGRect) {
// Drawing code
}
*/
public func printHello() {
print("hello")
}
}
2)In your storyboard, drag a UIView into your vc, and set the class to CunstomView, you can see that in my red frame:
3)click the Show the Assistant Editor, and ctrl-drag the view to the vc, set the name custom:
4)then in your vc's viewDidload function, you call the public function:
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var custom: CunstomView!
override func viewDidLoad() {
super.viewDidLoad()
custom.printHello()
}
}
5)the result:
First question. When I do that, how to I reference that instance from
my code? I have a public function I would like to call that updates my
view but I don't know how to call it from my view controller
A: A view cannot exist by itself in app. You need viewcontroller to handle the custom view. Then in that VC, you can refer the view as IBOutlet.
Second question. I created an instance of the class from within my
view controller just playing around and I noticed the public function
I created isn't available with that instance. Can I create public
functions when I inherit from UIView?
A: You can create public function of custom view, just declare them in the header file. Then import the header in your VC. Then u can access it.
You can try to update your view from IB with the mothod below.
Objective-C:
-(void)awakeFromNib {
[super awakeFromNib];
//do something
}
Swift
override func awakeFromNib() {
super.awakeFromNib()
}
Second question
Do you mean the custom view don't answer the function you create within the view controller?
I have a custom class. It loads when the app starts. I have to change the view inside this class method.
Class:
import Foundation
class ChatManager {
class var sharedInstance: ChatManager {
struct Singleton { static let instance = ChatManager() }
return Singleton.instance
}
override init() {
super.init()
}
function changeView() {
//I need to change view here.
}
}
I can change the view inside a view controller but this class is not an UIViewController
What should I do ?
My suggestion would be to do it in UIViewController. Your class should not be responsible for the View part.
But that's not your question. What you could do is send YourView as a parameter to the function do some logic there and return it. If you have to resize YourView on several different location, then create method for that inside YourView class. If you use same logic for several different UIViews create BaseView and implement that method there, and then inherit in your views BaseView.
I have to mention it again, this is not the place to do any UI-related stuff.
This is how you pass your UIView through. I agree with Nick however, you should be doing View logic in a custom View class or the UIViewController class.
function changeView(yourView: UIView) {
//I need to change view here.
}
I agree with Nick. The answer is, don't. You should treat a view controller's views as private. Mucking around with a view controller's views violates the OOP principle of encapsulation.
If you insist on having an outside class make changes to your views, create an instance method in your class that takes a view as a parameter and then applies changes to that view. Then you can call the method from your view controller class to make changes to your view.
Here is a solution that requires a navigation controller. If you are unfamiliar with navigation controllers, I strongly recommend looking at a tutorial. They make life much easier for iOS developers. Sorry if that code is running off your screen.
// Switches to MyViewController, a class I have implemented somewhere else
func moveToMyView() {
if let navController = getNavigationController() {
// The Identifier was set in the Identity Inspector tab on the storyboard (The field is called "Storyboard ID")
if let myController = navController.storyboard?.instantiateViewControllerWithIdentifier( "myClassID" ) as? MyViewController {
// Switch to the newController
navController.pushViewController( exerciseController, animated: true )
}
}
}
// Returns the navigation controller if it exists
func getNavigationController() -> UINavigationController? {
if let navigationController = UIApplication.sharedApplication().keyWindow?.rootViewController {
return navigationController as? UINavigationController
}
return nil
}
I have some problems to use subclasses in Swift, hope someone can help me.
What I have
Two view controllers:
VC1 with just some UIButtons
EffectVC that do some animation depending on the button pressed on VC1
import UIKit
protocol viewAnimation {
func initialStateSet()
func finalStateSet()
}
class EffectVC: UIViewController {
#IBOutlet weak var mainImage: UIImageView!
override func viewDidLoad() {
super.viewDidLoad()
self.initialStateSet()
}
override func viewDidAppear(animated: Bool) {
self.finalStateSet()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
func initialStateSet() {
}
func finalStateSet() {
}
}
class GrowingEffect : EffectVC, viewAnimation {
override func initialStateSet() {
// some stuff
}
override func finalStateSet() {
// other stuff
}
}
The problem
Maybe a simple question but I can't do what I want in Swift: I need to set a subclass according to the button that is pressed.
In other words I need to present subclassed view controller from my VC1 according to which button is pressed on VC1.
If I press the first button for example I want to show the VC 2 with the class GrowingEffect for use some custom stuff (this stuff must change according to the selected button).
What I tried
use IBAction for create my subclassed VC2 and show it
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let destinationViewController : UIViewController = storyboard.instantiateViewControllerWithIdentifier("EffectVC") as! GrowingEffect
self.presentViewController(destinationViewController, animated: true, completion: nil)
but I got
Could not cast value of type 'ViewAnimationDemo.EffectVC'
(0x109948570) to 'ViewAnimationDemo.GrowingEffect' (0x109948650).
use PrepareForSegue
but I can't set any subclass
What I really want to do
I know there are some other solution, like not using storyboard, but now I describe exactly what I want to do, hoping this is possibile:
have only one view controller in IB (EffectVC) associate with the class EffectVC. The class EffectVC has some subclasses like GrowingEffect.
In my code I want to instantiate the view controller EffectVC with the subclass that I need: for example instantiate the view controller in IB EffectVC with the class GrowingEffect.
I know that if I have one view controller for every subclass of EffectVC I can do what I want but I don't want so many view controller in IB because they are equal, the only things that I want to change are 2 methods.
I think there are some things mixed up in your setup. You should have 2 view controllers, each set up in its file, and each present in the storyboard with its identifier. It is ok if GrowingEffect inherits from EffectVC.
What you currently do with as! GrowingEffect is actually trying to cast the UIViewController instance you get from calling instantiateViewControllerWithIdentifier("EffectVC") to GrowingEffect. This will not work, because it is of type EffectVC.
Rather, you need to call instantiateViewControllerWithIdentifier("EffectVC") if button X is pressed, and instantiateViewControllerWithIdentifier("GrowingEffect") if button Y is pressed.
EDIT
If you use storyboard, you have to instantiate view controllers using instantiateViewControllerWithIdentifier. But you can only get an instance of GrowingEffect, if it is present on the storyboard.
It is not possible to "cast" an instance of EffectVC to GrowingEffect once created.
So, you have two possibilities here:
Use storyboard and put both view controllers on it. Use instantiateViewControllerWithIdentifier to instantiate the view controller you need, depending on the button pressed.
Do not use storyboard. Then you can create the needed view controller manually and use your UINavigationController's pushViewController method to present it.
You can't cast from parent class to child class, parent class just doesn't have the capacity to know what the child is doing. You can however cast from a child to parent, so you would want to set your view controller as GrowingEffect, then cast it to Effect, but again there is no strong suit to doing this either unless some method needs the parent class and you are using the child class. It looks like you need a redesign of how you want your view controllers laid out. Now I am assuming you have 2 children, lets call GrowingEffect and ShrinkingEffect. In your designer, you set your 1 to GrowingEffect and the other to ShrinkingEffect and make sure they have unique identifiers. Then you can use your view to present an Effect, and pass in either of those objects.