My app uses images which can have various statuses so I am using custom properties as tags. This works ok, but my tap gesture recognizer can't seem to access these properties. When the image is tapped, I need the action to depend on the state of these properties. Is there a way the gesture recognizer can read these custom properties from the tapped subclassed UIImageView or should I take a different approach? Thanks!
public class advancedTagUIImageView: UIImageView {
var photoViewedStatus: Bool?
var photoLikedStatus: Bool?
}
viewDidLoad() {
let imageView = advancedTagUIImageView(frame:CGRect(origin: CGPoint(x:50, y:50), size: CGSize(width:100,height:100)))
imageView.image = UIImage(named: dog.png)
imageView.photoViewedStatus = false
imageView.photoLikeStatus = false
imageView.tag = 7
imageView.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(soundTapped)))
view.addSubview(imageView)
}
#objc func soundTapped(gesture: UIGestureRecognizer) {
let photoTag = gesture.view!.tag // this works great
let isPhotoLiked = gesture.view!.photoLikeStatus // this doesn't work
// do whatever
}
Swift is strongly typed. The type of the gesture.view property is UIView which doesn't have the properties defined in your advancedTagUIImageView class. This is because you could theoretically also attach your UITapGestureRecognizer to any other type of view. In which case the program would crash on your soundTapped method, because you're just assuming that gesture.view is an advancedTagUIImageView which might not always be the case.
For the compiler to let you access these properties you need first check if gesture.view is really your sublcass like this:
if let photoView = (gesture.view? as? advancedTagUIImageView) {
// you can access your tags here
let isPhotoLiked = photoView.photoLikeStatus
} else {
// you might want to handle the case that the gesture was invoked from another view. If you're certain this should not happen, maybe just throw an assertion error to get notified in case it still does.
}
PS: According to the Swift API Design Guidelines type names should be capitalized, so in your case it should be AdvancedTagUIImageView. Not following these guidelines might not crash your program, but doing so might make your life a lot easier should you ever need to write code together with other people.
Related
In my viewController I have programmatically created several squares as sub-views.
Imagine it as a chessboard.
I would like to implement a method that executes some actions upon the sub-view (e.g., change the background color of a single square) when it gets touched by the user.
I have unsuccessfully tried with the UITapGestureRecognizer - I have read from Apple documentation that it applies only to one view at a time.
Do you have any suggestions?
Many thanks
You can subclass UIWindow class and handle all the events in - (void)sendEvent:(UIEvent *)event there like sending notifications to all the views or communicate with some other way. Check the following repository for more info:
https://github.com/mwinoto/TapDetectingWindow
Do it like this
class YourCustomView : UIView {
func addTapGesture(action : #escaping ()->Void ){
self.gestureRecognizers?.forEach({ (gr) in
self.removeGestureRecognizer(gr)
})
let tap = MyTapGestureRecognizer(target: self , action: #selector(self.handleTap(_:)))
tap.action = action
tap.numberOfTapsRequired = 1
self.addGestureRecognizer(tap)
self.isUserInteractionEnabled = true
}
}
or you can use this even in a extension of UIView if you're going to use it in multiple types of UIViews.
And then use it like:
let yourView = YourCustomView()
yourView.addTapGesture{[weak self] in
//implement tap event here
}
Notice that [weak self] is going to avoid getting a strong reference for closure to avoid a retain cycle there.
When using a UITableView and UISearchBar in swift, I was trying to find a way to keep the cancel button on the search bar enabled when the user searches something then scrolls in the table view, so they don't have to click twice to cancel the search. The default behaviour for resigning the first responder (or ending editing on the search bar) will gray out the cancel button, but I wanted to keep it enabled, so on Stackoverflow I found how to do this, but I can't find an answer online as to what searchBar.value(forKey: "cancelButton") does in the code below. Obviously it's somehow creating a reference to the cancel button on the search bar, but I don't understand what .value does (as I'm new to swift), and where the "cancelButton" key is coming from. I have read the func value(forKey key: String) documentation, but I still didn't understand it. It would be great if someone could explain what this is doing.
func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
searchBar.resignFirstResponder()
// If the user scrolls, keep the cancel button enabled
if let cancelButton = searchBar.value(forKey: "cancelButton") as? UIButton { // <-- This line
if searchBar.text != "" { cancelButton.isEnabled = true }
else { searchBar.showsCancelButton = false }
}
}
Thanks in advance.
UISearchBar is a subclass of
UIView -> UIResponder -> NSObject
And all NSObjects are conforming the NSKeyValueCoding Protocol Reference
valueForKey: is a KVC method. It works with ANY NSObject class and anything else that conforms to the above protocol. valueForKey: allows you to access a property using a string for its name. So for instance, if I have an Account class with a property number, I can do the following:
let myAccount = Account(number: 12)
myAccount.value(forKey: "number")
Since it is a runtime check, it can't be sure what the return type will be. So you have to cast it manually like:
let number = myAccount.value(forKey: "number") as? Int
I'm not going to explain the downcast and optionals here
So you can access any property of an object that conforms to NSKeyValueCoding just by knowing its method's exact name (that can be found easily by a simple reverse engineering).
Also, there is a similar method called performSelector that lets you execute any function of the object
⚠️ But be aware that Apple will reject your app if you touch a private variable or function of a system. (If they found out!)
⚠️ Also, be aware that any of these can be renamed without notice and your app will face undefined behaviors.
I was running into the same problem as you for searching through a list but I realized you can implement UITextfields instead...
Using didReturn to do textfield.resignFirstResponder() and when it resigns to take the value using textfield.value to search through a list.
In searchbar for iOS 12 or below, to access the elements you can use key value to access the elements. Like this function -
private func configureSearchBar() {
searchBar.barTintColor = Color.navBarColor
searchBar.makeRounded(cornerRadius: 5, borderWidth: 1, borderColor: Color.navBarColor)
searchBar.placeholder = searchBarPlaceholderText
searchBar.setImage(Images.search_white, for: .search, state: .highlighted)
searchBar.setImage(Images.green_check, for: .clear, state: .normal)
if let textField = searchBar.value(forKey: "searchField") as? UITextField {
textField.textColor = .white
textField.attributedPlaceholder = NSAttributedString(string: textField.placeholder ?? "", attributes: [NSAttributedString.Key.foregroundColor: UIColor.white])
let leftSideImage = textField.leftView as? UIImageView
leftSideImage?.tintColor = .white
}
if let cancelButton = searchBar.value(forKey: "cancelButton") as? UIButton {
cancelButton.setTitleColor(.white, for: .normal)
}
}
Here by using the keys we are accessing the elements of the searchbar.
I have a function that creates a button with a selector function as a target. The address of a button gets passed to handleSelectPhoto.
lazy var image1Button = createButton(selector: #selector(handleSelectPhoto))
func createButton(selector: Selector) -> UIButton {
let button = UIButton(type: .system)
button.addTarget(self, action: selector, for: .touchUpInside)
return button
}
#objc func handleSelectPhoto(button: UIButton) {
// Do something with button, this works
}
Now, I am trying to change the class of the above from UIButton to UIImageView like the following,
lazy var image1Button = createButton(selector: #selector(handleSelectPhoto))
func createButton(selector: Selector) -> UIImageView {
let view = UIImageView()
view.addGestureRecognizer(UITapGestureRecognizer(target: self, action: selector))
view.isUserInteractionEnabled = true
return view
}
#objc func handleSelectPhoto(button: UIImageView) {
// HERE, button does not get passed
}
With the above changes, in handleSelectPhoto, button instance is not correct. I can not read it as UIImageView type.
If I add a selector function using addGestureRecognizer, does it behave differently than adding a selector function using addTarget, in terms of how selector function is executed with parameters? Maybe I am not understanding how this selector function works...
Adding a target to something like UIGestureRecognizer or UIButton only passes one parameter to the selected function. This parameter depends on the type you are about to add the target on.
In your case the first code snippet works because you are adding a target to an UIButton, so your selected function gets passed this UIButton instance.
In your second scenario you add the target to an UITapGestureRecognizer, so the passed instance will be exactly this gesture recognizer, which cannot be of type UIImageView.
So the difference from the target parameter perspective between UIGestureRecognizer and UIButton is no difference. They both pass their instances to the selected function.
From the UIView subclass perspective there is the difference that UIGestureRecognizer is not a subclass of UIView, but UIButton is. That's why you can just use the passed UIButton instance in your first snippet. In the second snippet you need use the view property of UIGestureRecognizer.
guard let imageView = gestureRecognizer.view as? UIImageView else { return }
Besides your actual question it seems important to clarify how to write #selectors correctly. You're doing it correct already. No change necessary. Some may say you need to add (_:) or : to your selector like so: #selector(handleSelectPhoto(_:)) but this isn't true. In general, you only need to add these special characters when you are selecting a method which has an overload method with a different amount of parameters, but the same base name.
You should make your tell while setting the selection that your function will accept a parameter by adding : at the end of method name.
lazy var image1Button = createButton(selector: #selector(handleSelectPhoto:))
UIKit will automatically understand that the selector methods parameter will be of type UITapGestureRecognizer. Now rewrite the below method like this and you will be good to go.
#objc func handleSelectPhoto(gesture: UITapGestureRecognizer) {
if let buttonImageView = gesture.view as? UIImageView {
//Here you can make changes in imageview what ever you want.
}
}
I'm trying to move my fully functioning swipe gesture code into a view model to clean up the view controller but the code uses a lot of self and view references, so I suppose I need to pass along the view or UIView.self as an argument when calling the function. Can't get it to work though. Tried:
vm.swipeCode(myView: self.view)
func swipeCode(myView: UIView) {...
But it crashes. After some research I also tried variations of inout and & but to no avail. Here's the full swipe code (it references back to the view controller but I will move those as well when things start working :) )
var myVC = RecipesViewController()
func swipeCode(myView: UIView) {
//SWIPE RIGHT
let swipingRight = UISwipeGestureRecognizer()
swipingRight.addTarget(self, action: #selector(myVC.swipeRight))
swipingRight.direction = .right
swipingRight.delegate = self as? UIGestureRecognizerDelegate
swipingRight.cancelsTouchesInView = false
myView.isUserInteractionEnabled = true
myView.addGestureRecognizer(swipingRight)
//// ALLOW SWIPE LEFT ////
let swipingLeft = UISwipeGestureRecognizer()
swipingLeft.addTarget(self, action: #selector(myVC.swipeLeft))
swipingLeft.direction = .left
swipingLeft.delegate = self as? UIGestureRecognizerDelegate
swipingLeft.cancelsTouchesInView = false
myView.isUserInteractionEnabled = true
myView.addGestureRecognizer(swipingLeft)
}
The crash is probably because of these two lines:
swipingRight.addTarget(self, action: #selector(myVC.swipeRight))
swipingLeft.addTarget(self, action: #selector(myVC.swipeLeft))
You passed myVC.swipeLeft as the action, but self as the target, so the gesture recogniser will try to find a swipeLeft method in self, which doesn't exist.
You should always ensure that the action is a member of the target:
swipingRight.addTarget(myVC, action: #selector(myVC.swipeRight))
swipingLeft.addTarget(myVC, action: #selector(myVC.swipeLeft))
You should simply make a UIView or UIViewController inherited class instead if your methods use a lot of self then simply make your controllers or views of that class.
class CustomViewController:UIViewController {
func swipeCode(myView: UIView) {
// Your code here
}
// Any other methods your code might need
}
class RecipesViewController:CustomViewController {
// Whatever else your view controller is made from
}
Or if your code swiping works in every view controller you could also extends the UIViewController to add those functionnalities
I'm trying to get a very basic NSPageController to work (in book mode, not history mode). It will successfully transition once, and then stop working.
I suspect I'm creating the NSImageViews I'm loading into it wrong, but I can't figure out how.
The storyboard has a the SamplePageController which holds in initial hard-coded NSImageView.
I suspect I'm missing something really obvious here, since all of the tutorial's I've found for NSPageController are in Objective C not swift, and tend to focus on the history view mode.
The code is:
import Cocoa
class SamplePageController: NSPageController, NSPageControllerDelegate {
private var images = [NSImage]()
#IBOutlet weak var Image: NSImageView!
//Gets an object from arranged objects
func pageController(pageController: NSPageController, identifierForObject object: AnyObject) -> String {
let image = object as! NSImage
let image_name = image.name()!
let temp = arrangedObjects.indexOf({$0.name == image_name})
return "\(temp!)"
}
func pageController(pageController: NSPageController, viewControllerForIdentifier identifier: String) -> NSViewController {
let controller = NSViewController()
let imageView = NSImageView(frame: Image.frame)
let intid = Int(identifier)
let intid_u = intid!
imageView.image = images[intid_u]
imageView.sizeToFit()
controller.view = imageView
return controller
// Does this eventually lose the frame since we're returning the new view and then not storing it and the original ImageView is long gone by then?
// Alternatively, are we not sizing the imageView appropriately?
}
override func viewDidLoad() {
super.viewDidLoad()
images.append(NSImage(named:"text")!)
images.append(NSImage(named:"text-2")!)
arrangedObjects = images
delegate = self
}
}
In this case your pageController.view is set to your window.contentView and that triggers the warning. What you need to do is add a subview in the window.contentView and have your pageController.view point to that instead.
The reason for the warning is that since NSPageController creates snapshots (views) of your content history, it will add them at the same level as your pageController.view to transition between them: that means it will try to add them to pageController.view.superview.
And if your pageController.view is set to window.contentView, you are adding subviews to the window.contentView.superview, which is not supported:
New since WWDC seed: NSWindow has never supported clients adding subviews to anything other than the contentView.
Some applications would add subviews to the contentView.superview (also known as the border view of the window). NSWindow will now log when it detects this scenario: "NSWindow warning: adding an unknown subview:".
Applications doing this will need to fix this problem, as it prevents new features on 10.10 from working properly. See titlebarAccessoryViewControllers for official API.