如何在watchOS6中注入.environmentObject() [英] How to inject .environmentObject() in watchOS6

问题描述

我想在watchOS6中创建SwiftUI视图时注入一个EnvironmentObject.

I want to inject an EnvironmentObject while creating a SwiftUI view in watchOS6.

但是由于WKHostingController需要具体类型，所以我无法执行以下ContentView().environmentObject(UserData())

But since WKHostingController expects a Concrete type I am not able to do the following ContentView().environmentObject(UserData())

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

此代码失败，并出现以下错误:

This code fails with the following error:

无法将某些视图"类型的返回表达式转换为"ContentView"类型

Cannot convert return expression of type 'some View' to return type 'ContentView'

我看到了这样的解决方法: 在watchOS中使用environmentObject ，这似乎是一种hack，而不是适当的解决方案.

I have seen workaround like this : Using environmentObject in watchOS this seems like a hack instead of a proper solution.

我在Twitter上问了一个watchOS工程师，他的回答是将.environmentObject(UserData())放在ContentView()的主体内.我尝试这样做，但是Xcode报告错误.

I asked a watchOS engineer on Twitter regarding the same and his reply was to place .environmentObject(UserData()) inside the body of ContentView(). I tried doing that but Xcode reports an error.

那么有没有人找到一种方法来做同样的事情?

So has anyone found a way to do the same ?

推荐答案

链接的替代方法使用AnyView，这是一个非常糟糕的主意.苹果工程师在其他几个问题和推文中已经解释说，AnyView只应在叶子视图上使用，否则会严重影响性能.

The workaround from the link uses AnyView, which is a very bad idea. It has been explained in several other questions and tweets from Apple engineers, that AnyView should only be used on leaf views, as there is a heavy performance hit otherwise.

对于第二个选项(将environmentObject放在ContentView内)，它可以正常工作.这里有一个例子:

As for the second option (put the environmentObject inside ContentView), it works fine. Here you have an example:

class UserData: ObservableObject {
    @Published var show: Bool = true
}

struct ContentView: View {
    @State var model = UserData()

    var body: some View {
        SubView().environmentObject(model)
    }
}

struct SubView: View {
    @EnvironmentObject var model: UserData

    var body: some View {
        VStack {
            Text("Tap Me!").onTapGesture {
                self.model.show.toggle()
            }

            if self.model.show {
                Text("Hello World")
            }
        }
    }
}

这篇关于如何在watchOS6中注入.environmentObject()的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！