SwiftUI:如何在`$` 可绑定对象运算符之前使用`!` 运算符?

问题描述

我无法对 Bindable $ 对象使用逻辑非 ! 运算符.

这是我想要的场景-

struct ContentView: View {
@State private var isLoggedIn:Bool = true
var body: some View {

    Text("Root View")
        .sheet(isPresented: !self.$isLoggedIn) {
            SignInView()
        }
        .onAppear { self.performAuthentication() }
   }
}

登录视图应该在我通过某些按钮操作设置 isLoggedIn = false 后立即显示.为此，我必须在 $ 之前使用逻辑非运算符.

Sign In View should present as soon as I set isLoggedIn = false by some button action. For which I have to use logical not operator before $.

编译器错误:无法将绑定"类型的值转换为预期的参数类型 'Bool'

我怎样才能做到这一点?

How can I achieve this?

推荐答案

正如我在对问题的评论中所说，有针对 SwiftUI 发布的方法: 将 Binding 转换为另一个 Binding.但是，如果您希望将其明确作为运算符，则可以使用以下内容(经过测试并适用于 Xcode 11.2)

As I said in comment to question there were approach posted for SwiftUI: transform Binding into another Binding. If you, however, want to have it explicitly as operator, you can use the following (tested & works with Xcode 11.2)

extension Binding where Value == Bool {
    static prefix func !(_ lhs: Binding<Bool>) -> Binding<Bool> {
        return Binding<Bool>(get:{ !lhs.wrappedValue },
                             set: { lhs.wrappedValue = !$0})
    }
}

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