问需要帮助维护Swift环境对象
EN

Stack Overflow用户

提问于 2022-01-11 11:35:04

回答 1查看 61关注 0票数 0

尝试使用SwiftUI将ViewController视图放置到ViewController中，但收到以下错误：

未发现ObservableObject型UIStateModel。作为此视图的祖先，可能缺少用于View.environmentObject(_:)的UIStateModel。

所有的帮助都很感激，我被困住了。

ViewController.swift

class ViewController: UIViewController {
    @EnvironmentObject var UIModel: UIStateModel
    var uiState: UIStateModel = UIStateModel()
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        addCarousel()
    }
    
    func addCarousel(){
        let snapC : SnapCarousel
        let contentView : UIHostingController<SnapCarousel>
        uiState = UIStateModel()
        snapC = SnapCarousel( UIState: uiState )
        contentView = UIHostingController(rootView: snapC)
        addChild(contentView)
        view.addSubview(contentView.view)
        contentView.didMove(toParent: self)
    }
    
}

Carousel.swift

struct SnapCarousel: View {
    var UIState: UIStateModel
    //Carousel instantiation 
}

struct Card: Decodable, Hashable, Identifiable {
    //code
}

public class UIStateModel: ObservableObject {
    @Published var activeCard: Int = 0
    @Published var screenDrag: Float = 0.0
}

struct Carousel<Items : View> : View {
    @EnvironmentObject var UIState: UIStateModel
    //card management
}

struct Canvas<Content : View> : View {
// view manager 
}

struct Item<Content: View>: View {
    @EnvironmentObject var UIState: UIStateModel
   //code for card view
}

ios

swift

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回答 1

Stack Overflow用户

发布于 2022-01-11 12:00:01

您需要将UIStateModel注册为@EnvironmentObject，以便可以将其自动注入子视图中。

首先，更新SnapCarousel以保存environmentObject：

struct SnapCarousel: View {
    @EnvironmentObject var UIState: UIStateModel
    //Carousel instantiation 
}

若要将模型注册为环境对象，当使用SnapCarousel注册为：

let snapC = SnapCarousel()
snapC.environmentObject(uiState)

如果不需要引用uiState，则可以将整个过程简化为：

class ViewController: UIViewController {

  override func viewDidLoad() {
    super.viewDidLoad()
    addCarousel()
  }

  func addCarousel() {
    let controller = UIHostingController(rootView: SnapCarousel().environmentObject(UIStateModel()))
    addChild(controller)
    view.addSubview(controller.view)
    controller.didMove(toParent: self)
    
    // add some constraints to fill the parent view
    NSLayoutConstraint.activate([
      controller.view.widthAnchor.constraint(equalTo: view.widthAnchor),
      controller.view.heightAnchor.constraint(equalTo: view.heightAnchor),
      controller.view.centerXAnchor.constraint(equalTo: view.centerXAnchor),
      controller.view.centerYAnchor.constraint(equalTo: view.centerYAnchor)
    ])
  }
}