价值观察者没有正确沟通

Question

点击手势由以下函数触发；

@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()
    }

用户卡视图模型：

...        
    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
    }

索引改变时需要触发相关的闭包。 下面的对象在相关视图中。

var userCards: UserCardViewModel! {
        didSet{
            userCards.imageIndexObserver = { index, image in
                self.showingImage.image = self.userCards.userImages[index]
                print(index)                
           }
        }
    }

前两次点击时，我无法在索引语句上方打印。当我在图像上按下右侧时（相关数组计数为 2）

• 第一次点击；什么都没有发生。
• 第二次点击；打印 0。
• 第三次，它打印 index = 1。

我正在这样初始化（来自相关的视图控制器）

convenience init(userCards: UserCardViewModel) {
        self.init(frame: .zero)
        self.userCards = userCards
        configure()
    }

Answer 1

我在视图中添加了手势。当您点击右侧索引计数会增加（左侧会减少），一旦达到数组计数，它将再次从 0 开始。

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()
     }
}

这是模型类

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
       }
}

最初imageIndex 是0

1) 开始时点击右侧imageIndex 将变为 1

2) 开始时点击左侧imageIndex 将变为 (yourArray.count - 1)

从here下载演示