Using the new 2.2 version of Swift, I cannot use the #selector to invoke a method defined inside an extension from the (same) extension. The compiler says unresolved itendifier for doSomething(_:).
extension UIViewController {
func doSomething(){
//...
}
func setTapGestureRecognizer(){
let recognizer = UITapGestureRecognizer(target: self, action: #selector(doSomething(_:))) //unresolved itendifier
view.addGestureRecognizer(recognizer )
}
}
I already tried to mark the method doSomething() with #objc without success.
your func has no input parameters.
Fix it to:
func setTapGestureRecognizer(){
let recognizer = UITapGestureRecognizer(target: self, action: #selector(doSomething))
view.addGestureRecognizer(recognizer)
}
Related
I want to invoke a Swift closure in Objective-C.
There is an error like this even though I declared the function:
No visible #interface for “User” declares the selector “isReady”
Swift:
#objcMember
class User:NSObject {
func isReady(isTrue: Bool) -> Bool {
return true
}
}
Objective-C:
User *user = [[User alloc] init];
[_user isReady]. <- error
Add to the function #objc modifier:
#objcMember
class User:NSObject {
#objc public func isReady(isTrue: Bool) -> Bool {
return true
}
}
And add public modifier to the function to allow access from other modules (swift code builds as module and ObjC code should export it and access via open interfaces).
I've come to Swift from Objective-C and there's a lot of things that Objective-C can do but swift is much more complicated. Such as OOP dynamic initializer.
E.g. I've got this code working in Objective-C:
#interface CommonVC: UIViewController
+ (instancetype)showFrom:(UIViewController *)vc;
#end
#implementation CommonVC
+ (instancetype)showFrom:(UIViewController *)vc {
CommonVC *instance = [self instantiateFrom:vc.nibBundle];
[vc presentViewController:instance animated:YES completion:nil];
return instance;
}
// this is like convenience initializer.
+ (instancetype)instantiateFrom:(NSBundle *)aBundle {
return [self.alloc initWithNibName:NSStringFromClass(self.class) bundle:aBundle];
}
#end
#interface SubClassVC: CommonVC
#end
And then use the subclass or superclass like this:
SubClassVC *subVC = [SubClassVC showFrom:self];
// or in swift:
SubClassVC.show(from: self)
However, in swift, it seems impossible to implement something like that. I've tried a few, but always got compile error. Here's one:
class CommonVC: UIViewController {
class func show(from sender: UIViewController) -> Self {
let vc = self(sender: sender) // Compiler error: Constructing an object of class type 'Self' with a metatype value must use a 'required' initializer
sender.present(vc, animated: true, completion: nil)
return unsafeDowncast(vc, to: self)
}
convenience init(sender: UIViewController) {
self.init(nibName: type(of: self).className, bundle: sender.nibBundle)
loadView()
}
}
So how do I write generic convenience initializer of a viewController from the super class and then call that with the subclass?
Of course, my convenience init has lots of stuff that I just cut down to this simple code, also the function show(from:) has a different presentation instead of this simple present(_:animated:completion:).
Even if I make a function to do the setup after initialize, it still wouldn't work
class CommonVC: UIViewController {
class func show(from sender: UIViewController) -> Self {
let vc = self.init(nibName: type(of: self).className, bundle: sender.nibBundle) // Compiler error: Constructing an object of class type 'Self' with a metatype value must use a 'required' initializer
vc.setupAfterInitialize()
sender.present(vc, animated: true, completion: nil)
return unsafeDowncast(vc, to: self)
}
convenience init(sender: UIViewController) {
self.init(nibName: type(of: self).className, bundle: sender.nibBundle)
setupAfterInitialize()
}
internal func setupAfterInitialize() {
// do stuff
loadView()
}
}
And the code looks stupid, doesn't make convenience init convenience.
For now, I can't use the class function show(from:) but have move the presentation outside and make things like:
CommonVC.show(from: self)
SubClassVC(sender: self).present()
// instead of this simple presentation:
// SubClassVC.show(from: self)
I've even tried this but still not working:
class func show<T: CommonVC>(from sender: UIViewController) -> Self {
T.init(nibName: type(of: self).className, bundle: sender.nibBundle)
....
When you switch from Objective-C to Swift, it's tempting to simply translate your Objective-C style into Swift code. But Swift is fundamentally different in some ways.
It may be possible to implement a generic class which all your controllers are subclass of, but we tend to try and avoid inheritance in Swift where possible (in favour of protocols and extensions).
A good Swift rule of thumb, from Apple, is: "always start with a protocol"...
It's actually very easy to implement what you want using a protocol, and extension:
protocol Showable {
init(className: String, bundle: Bundle?)
static func show(from: UIViewController) -> Self
}
extension Showable where Self: UIViewController {
init(className: String, bundle: Bundle?) {
self.init(nibName: className, bundle: bundle)
}
static func show(from: UIViewController) -> Self {
let nibName = String(describing: self)
let instance = self.init(className: nibName, bundle: from.nibBundle)
from.present(instance, animated: true, completion: nil)
return instance
}
}
In the above code, I've declared a Showable protocol and an extension that provides a default implementation that applies where the adopting class is an instance of UIViewController.
Finally, to provide this functionality to every single view controller in your project, simply declare an empty extension:
extension UIViewController: Showable { }
With these two short snippets of code added you can now do what you describe in your question (as long as an appropriately named nib exists for your view controller instance):
let secondController = SecondViewController.show(from: self)
ThirdController.show(from: secondController)
And that's the beauty of Swift. All your UIViewController subclasses now get this functionality for free; no inheritance required.
I have a UIBarButtonItem subclass, "NavBarButtonItem", defined in Swift 3.0 but am not sure if I've set up the convenience initializer properly. This initializer seems works fine in other Swift classes:
let nextBarButtonItem = NavBarButtonItem.init(self, "Next", #selector(pressedNextButton))
However, in Obj-C, Xcode presents me with the following (it's missing argument labels):
self.nextButton = [NavBarButtonItem alloc] init:<#(id<NavBarButtonDelegate> _Nonnull)#> :<#(NSString * _Nonnull)#> :<#(SEL _Nonnull)#>
and I've completed it with:
self.nextButton = [[NavBarButtonItem alloc] init:rvc :2 :#"Next" :#selector(doneButtonTapped:)];
I've not set up initializers in Swift before so suspect that there might be something wrong but the app compiles. Here's the Swift subclass:
MyViewController.swift
// this file contains other classes that precede subclass NavBarButtonItem
..
#objc protocol NavBarButtonDelegate {
func pressedNextButton()
}
#objc class NavBarButtonItem: UIBarButtonItem
{
private var delegate: NavBarButtonDelegate?
init(_ delegate: NavBarButtonDelegate){
self.delegate = delegate
super.init()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
convenience init(_ delegate: NavBarButtonDelegate, _ title: String, _ selector: Selector)
{
self.init(delegate, wtfProperty)
self.title = title
self.action = selector
}
}
I just implemented Chartboost into my all swift app.
I have rewarded interstitials. So I need to set up a delegate using the objective C function Chartboost gave me. I cannot figure out how to do it. This is how I did Admob via Swift.
NSNotificationCenter.defaultCenter().addObserver(self, selector: "presentInterstitial:", name: "AdMobCall", object: nil)
func presentInterstitial(sender:UIButton!) {
if let isReady = interstitial?.isReady { // _ isReady
interstitial?.presentFromRootViewController(self)
}
}
NSNotificationCenter.defaultCenter().postNotificationName("AdMobCall", object: nil)
But the Objective C Chartboost function I am given is:
(void)didCompleteRewardedVideo:(CBLocation)location
withReward:(int)reward;
And I do not understand how to create the same delegate I did for Admob using this function. it doesn't seem possible. I have the Chartboost rewarded intersitials working. But I have no way of setting up the delegate to see if they watched the video to completion or not.
If you want achieve objective-c delegate in to swift. You need to do following steps.
Need to create bridge file to import your objective-c classes
//
// Use this file to import your target's public headers that you would like to expose to Swift.
//
#import "UVIViewController.h"
You need to extend the protocol name in your swift viewcontroller
import UIKit
class ViewController: UVIViewController, UVIDataRefreshProtocol { // 2. Extend Protocal
var secondController: DelegateViewController?
#IBOutlet var delegateRefresh: UILabel!
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
self.registerForBasicDataRefreshNotification(); // 3. Register the protocol notification
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
// Register the protocol notification with same name. Example : DataRefreshNotification
override func registerForBasicDataRefreshNotification() {
self.validateBasicDataRefreshNotification();
NSNotificationCenter.defaultCenter().addObserver( // 4. Register the protocol notification with same name.
self,
selector: "basicDataDidRefresh",
name: DataRefreshNotification,
object: nil)
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
delegateRefresh.text = "";
if segue.identifier == "view_to_delegate" {
secondController = segue.destinationViewController as? DelegateViewController
}
}
// Basic Data Did Refresh Notification
func basicDataDidRefresh() { // 4. Event will be triggered while calling the protocol post notification. called with same name
NSLog("\n Basic data is refreshed")
delegateRefresh.text = "Basic data is refreshed";
}
}
5. NSNotificationCenter.defaultCenter().postNotificationName(DataRefreshNotification, object: nil) // Call the notification.
Sample Project: https://github.com/vigneshuvi/Objective-C-Delegate-Swift
I have two delegates like this:
protocol MyFirstDelegate {
func change(value: int)
}
protocol MySecondDelegate {
weak var delegate: MyFirstDelegate?
}
Those protocols are implemented in two customized UIViewControllers:
class MyFirstViewController: UIViewController, MyFirstDelegate {
...
}
class MySecondViewController: UIViewController, MySecondDelegate {
...
}
The first UI view controller will push second UI view controller by using a segue.
In my first UI view controller class I have the following codes to prepare segue:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?)
{
if let vc = (segue.destinationViewController) as? MySecondViewController {
vc.delegate = self
}
}
The above codes compile without any problem. However, I think that the first UI controller has knowledge about the next view controller class. I prefer to pass delegate like this:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?)
{
if var vc = (segue.destinationViewController) as? MySecondDelegate {
vc.delegate = self
}
}
I got compiling error:
Cannot assign to property: "vc" is immutable.
It seems that as to a concrete UI view controller is OK, but not to a protocol. Any explanation and solution to this?
By the way, in Objective-C, this can be done like this:
id<NSObject, MySecondDelegate> vc = segue.destinationViewController;
vc.delegate = self;
I could not find a way in swift to define a variable like
let vc: AnyObject<type>? // like id<type>
UPDATES
As #David_Berry solution, it works if I mark protocol as class. The above codes are actually simplified ones. I am in the middle of converting my ObjC codes to Swift. Therefore, I have to mark protocols as objc:
#objc protocol MyFirstDelegate : class {
func change(value: int)
}
#objc protocol MySecondDelegate {
weak var delegate: MyFirstDelegate?
}
with #objc, I still get the same compiling error.
Well, I finally managed to get your example to compile, you have a LOT of inconsistencies. The key to your actual problem, I think, is requiring that the protocols be class protocols:
protocol XXX : class { }
Says that only types that are classes can be declared to implement XXX.
But, I'm really not sure that's your problem, there were so many other changes required (you spelled MySecondDelegate at least two ways, MySecondViewController at least two ways, etc.
The compiling example is:
// This protocol has to be class so that delegate can be weak
protocol MyFirstDelegate : class {
func change(value: Int)
}
protocol MySecondDelegate {
weak var delegate: MyFirstDelegate? { get set }
}
class MyFirstViewController: UIViewController, MyFirstDelegate {
func change(value: Int) {
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?)
{
if var vc = (segue.destinationViewController) as? MySecondDelegate {
vc.delegate = self
}
}
}
class MySecondViewController: UIViewController, MySecondDelegate {
weak var delegate : MyFirstDelegate?
}
As for your question, there is no swift synonym to the objective-C syntax id<Protocol> or Class<Protocol> There are multiple duplicates to that issue that offer alternatives.