如何动态地在 SwiftUI 中以模态方式推送视图或呈现视图？

Question

我正在学习 SwiftUI，目前我的重点是实现一种我能够使用 UIKit 实现的方法。我需要创建一个方法来确定我是应该推送视图还是根据布尔值以模态方式呈现视图。

在 UIKit 中，我的代码是：

var presentVC = true // boolean that determines whether VC will be presented or pushed

let vc = ViewController() //Your VC that will be pushed or presented

if (presentVC == true) {
     self.presentViewController(vc, animated: true, completion: nil)
} else {
    self.navigationController.pushViewController(vc, animated: true)
}

但在 SwiftUI 中，我不确定如何使用以下方法正确实现：

NavigationLink - 用于推送视图
.sheet(isPresented:, content:) - 以模态方式呈现视图

NavigationLink 和 .sheet 修饰符似乎与视图实现耦合在一起。有没有人已经在 SwiftUI 中遇到并解决了这种情况？谢谢

我正在使用 SwiftUI 1.0，因为我需要支持 iOS 13.

Answer 1

一个可能的解决方案是创建一个具有可用表示类型的自定义枚举：

enum PresentationType {
    case push, sheet // ...
}

并创建用于激活不同视图的自定义绑定：

func showChildView(presentationType: PresentationType) -> Binding<Bool> {
    .init(
        get: { self.showChildView && self.presentationType == presentationType },
        set: { self.showChildView = [=11=] }
    )
}

完整代码：

struct ContentView: View {
    @State var presentationType = PresentationType.push
    @State var showChildView = false

    func showChildView(as presentationType: PresentationType) -> Binding<Bool> {
        .init(
            get: { self.showChildView && self.presentationType == presentationType },
            set: { self.showChildView = [=12=] }
        )
    }

    var body: some View {
        NavigationView {
            VStack {
                Button(action: {
                    self.presentationType = .push
                    self.showChildView = true
                }) {
                    Text("Present new view as Push")
                }
                Button(action: {
                    self.presentationType = .sheet
                    self.showChildView = true
                }) {
                    Text("Present new view as Sheet")
                }
            }
            .navigationBarTitle("Main view", displayMode: .inline)
            .background(
                NavigationLink(
                    destination: ChildView(),
                    isActive: self.showChildView(presentationType: .push),
                    label: {}
                )
            )
        }
        .sheet(isPresented: self.showChildView(presentationType: .sheet)) {
            ChildView()
        }
    }
}

struct ChildView: View {
    var body: some View {
        ZStack {
            Color.red
            Text("Child view")
        }
    }
}

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