在watchOS中使用environmentObject [英] Using environmentObject in watchOS

问题描述

我正在尝试在watchOS6应用中使用environmentObject将数据模型绑定到视图.

I am trying to use environmentObject in a watchOS6 app to bind my data model to my view.

我已经在Xcode 11中创建了一个简单的独立Watch应用.

I have created a simple, stand-alone Watch app in Xcode 11.

我创建了一个新的DataModel类

import Combine
import Foundation
import SwiftUI

final class DataModel: BindableObject {

    let didChange = PassthroughSubject<DataModel,Never>()

    var aString: String = "" {
        didSet {
            didChange.send(self)
        }
    }

}

在我的ContentView结构中，我使用@EnvironmentObject-

In my ContentView struct I bind this class using @EnvironmentObject -

struct ContentView : View {

    @EnvironmentObject private var dataModel: DataModel

    var body: some View {
        Text($dataModel.aString.value)
    }
}

最后，我尝试将DataModel的实例注入HostingController类中的环境-

Finally, I attempt to inject an instance of the DataModel into the environment in the HostingController class -

class HostingController : WKHostingController<ContentView> {
    override var body: ContentView {
        return ContentView().environmentObject(DataModel())
    }
}

但是，我得到一个错误:

But, I get an error:

Cannot convert return expression of type '_ModifiedContent<ContentView, _EnvironmentKeyWritingModifier<DataModel?>>' to return type 'ContentView'

错误是因为WKHostingController是需要具体类型的泛型-在这种情况下为WKHostingController<ContentView>.

The error is because the WKHostingController is a generic that needs a concrete type - WKHostingController<ContentView> in this case.

由于UIHostingController不是通用类，因此类似的方法也可以完美地与iOS应用程序中的UIHostingController配合使用.

A similar approach works perfectly with UIHostingController in an iOS app because UIHostingController isn't a generic class.

还有其他方法可以将环境注入watchOS视图吗?

Is there some other way to inject the environment to a watchOS view?

推荐答案

您可以使用类型擦除，对于SwiftUI View，可以使用AnyView.

You can use type erasure, AnyView in the case of SwiftUI View.

我将重构WKHostingController以返回AnyView.

这对我来说似乎编译的很好.

This seems to compile fine on my end.

class HostingController : WKHostingController<AnyView> {
    override var body: AnyView {
        return AnyView(ContentView().environmentObject(DataModel()))
    }
}

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