SwiftUI：为每个视图使用不同的环境对象

Question

在 SwiftUI 中，我有几个不同的屏幕。对于每个屏幕，我都有一个 ViewController、SwiftUI View 和一个组合的 EnvironmentObject。组合后的 EnvironmentObject 有两个 observable 类，一个是 ViewModel，另一个是 Interactor。

如何在不使用 ViewController 的情况下为每个 SwiftUI 视图使用 Interactor 和 ViewModel？并且每个 View 都有不同的 EnvironmentObject。

import SwiftUI
import Combine

class ViewModel1: ObservableObject {
    //Published data for view
    @Published var text: String

    init(text: String) {
        self.text = text
    }
}


class Interactor1<VC: UIViewController>: ObservableObject {

    let vc: VC
    let viewModel: ViewModel1?

    init(vc: VC, viewModel: ViewModel1?) {
        self.vc = vc
        self.viewModel = viewModel
    }

    func buttonClicked() {
        //present second ViewController by using vc.present...
    }
}


class CombinedObject<VC: UIViewController>: ObservableObject {
    @Published var interactor: Interactor1<VC>
    @Published var viewModel: ViewModel1

    var anyCancellable: AnyCancellable? = nil
    var anyCancellable2: AnyCancellable? = nil

    init(vc: VC, index: Int) {
        viewModel = ViewModel1(text: "text1")

        interactor = Interactor1(vc: vc, viewModel: nil)
        interactor = Interactor1(vc: vc, viewModel: viewModel)

        anyCancellable = interactor.objectWillChange.sink { (_) in
            self.objectWillChange.send()
        }

        anyCancellable2 = viewModel.objectWillChange.sink { (_) in
            self.objectWillChange.send()
        }
    }
}


class ViewController1: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let combinedObject = CombinedObject(vc: self, index: 0)
        let view1 = View1<ViewController1>().environmentObject(combinedObject)
        let hostingController = UIHostingController(rootView: view1)

        self.addChild(hostingController)
        hostingController.view.translatesAutoresizingMaskIntoConstraints = false
        self.view.addSubview(hostingController.view)
        hostingController.didMove(toParent: self)
    }
}


struct View1<VC1: UIViewController>: View {
    @EnvironmentObject var combinedObject: CombinedObject<VC1>

    var body: some View {
        VStack() {
            Button(action: {
                self.combinedObject.interactor.buttonClicked()
            }, label: {
                Text(self.combinedObject.viewModel.text)
                })
            }
    }
}

Answer 1

环境对象是按类型注入的，因此您可以分别注入视图模型和交互器，如下所示

struct View1<VC1: UIViewController>: View {
    @EnvironmentObject var viewModel: ViewModel1
    @EnvironmentObject var iterator: Interactor1<VC1>

    ...

它们将可用于所有子视图（两者，但独立，基于声明），例如

struct SubView1<VC1: UIViewController>: View { // only with view model
    @EnvironmentObject var viewModel: ViewModel1

struct SubView2<VC1: UIViewController>: View { // only with iterator
    @EnvironmentObject var iterator: Interactor1<VC1>

最后也是必需的，对于根视图，两者都必须在构造时注入，例如（scratchy）

View1(...)
   .environmentObject(ViewModel1(...))
   .environmentObject(Interactor1(...))

顺序无关紧要，按类型注入。

使用 Xcode 11.2 / iOS 13.2 测试