Value observers do not communicate correctly - swift

Question

Tap gesture get triggered by the below function;
#objc func handleTapGR(tapGR: UITapGestureRecognizer) {
let tapLocation = tapGR.location(in: nil)
let moveNext = tapLocation.x > frame.width / 2 ? true : false
moveNext ? userCards.nextImage() : userCards.previousImage()
}
UserCardViewModel:
...
var imageIndex: Int = 0 { didSet{ imageIndexObserver?(imageIndex, userImages[imageIndex]) } }
var imageIndexObserver: ((Int, UIImage) -> () )?
mutating func nextImage() {
imageIndex = imageIndex + 1 >= userImages.count ? 0 : imageIndex + 1
}
mutating func previousImage() {
imageIndex = imageIndex - 1 < 0 ? userImages.count - 1 : imageIndex - 1
}
Related closure needs to be triggered when the index is changed.
Below object is in related view.
var userCards: UserCardViewModel! {
didSet{
userCards.imageIndexObserver = { index, image in
self.showingImage.image = self.userCards.userImages[index]
print(index)
}
}
}
I am not able to get printed above the index statement at the first two taps.When I press right side on image (related array count is 2)
At first tap; nothing happens.
At second tap; prints 0.
At third, it prints index = 1.
I am initializing like that (from related viewcontroller)
convenience init(userCards: UserCardViewModel) {
self.init(frame: .zero)
self.userCards = userCards
configure()
}

Answer 1

I have added gesture on view. When you tap right side index count will increase (left side will decrease), once it reached on array count then it will starts from 0 again.
class ViewController: UIViewController {
var userCards = UserCardViewModel() {
didSet{
userCards.imageIndexObserver = { index, image in
//self.showingImage.image = self.userCards.userImages[index]
print(index) //<------- Here you will get index
}
}
}
override func viewDidLoad() {
super.viewDidLoad()
let img1 = UIImage(systemName: "arrow.up.right.video")
let img2 = UIImage(systemName: "arrow.up.right.video")
let img3 = UIImage(systemName: "arrow.up.right.video")
userCards.userImages = [img1!,img2!,img3!]
let tap = UITapGestureRecognizer(target: self, action: #selector(self.handleTap(_:)))
self.view.addGestureRecognizer(tap)
}
#objc func handleTap(_ tapGR: UITapGestureRecognizer) {
let tapLocation = tapGR.location(in: nil)
let moveNext = tapLocation.x > self.view.frame.width / 2 ? true : false
moveNext ? userCards.nextImage() : userCards.previousImage()
}
}
This is Model class
struct UserCardViewModel {
var userImages : [UIImage] = []
var imageIndex: Int = 0 {
didSet {
imageIndexObserver?(imageIndex, userImages[imageIndex])
} }
var imageIndexObserver: ((Int, UIImage) -> () )?
mutating func nextImage() {
imageIndex = imageIndex + 1 >= userImages.count ? 0 : imageIndex + 1
}
mutating func previousImage() {
imageIndex = imageIndex - 1 < 0 ? userImages.count - 1 : imageIndex - 1
}
}
Initially imageIndex is 0
1) At start when you tap on right side imageIndex will become 1
2) At start when you tap on left side imageIndex will become (yourArray.count - 1)
Download demo from here