初始化警报外部视图 - SwiftUI

Question

这几天一直在尝试解决这个问题，现在是我寻求帮助的时候了。我知道如何使用普通的 Swift 来做到这一点，但目前 SwiftUI 对我来说还是有点不同。我有一个检查某事是否属实的功能。它通过 3 个 if 语句，如果一个为真，则它返回一个我创建为真的布尔值。一旦 3 个中的一个为真，我希望弹出某个警报。我已在正文中粘贴了所有 3 个警报：一些带有正确变量的视图，但它没有显示任何内容。如果我注释掉 2 并保留 1 Alert 未注释，那么它可以工作。所以我知道我的 if 语句是正确的。这就是我如何将它呈现给身体的方式，这就是我坚持的地方。请参阅下文，如果您有其他选择。

    func showTip() {
            if (stepFive <= Float(18)) {
                under = true
            }

           else if (stepFive >= Float(18) && stepFive <= Float(18.5)) {
                thin = true
            }


           else if (stepFive >= 18.6) && (stepFive <= 24.9) {
                healthy = true
            }
    }

var body: some View {
        ZStack {
            Color.blue
            .edgesIgnoringSafeArea(.all)

            .alert(isPresented: $under) {
                Alert(title: Text("Results"), message: Text("A of less than 18 means you are under weight. "), dismissButton: .default(Text("OK")))
            }

            .alert(isPresented: $thin) {
                Alert(title: Text("Results"), message: Text("A of less than 18.5 indicates you are thin"), dismissButton: .default(Text("OK")))
            }

            .alert(isPresented: $healthy) {
                Alert(title: Text("Results"), message: Text("A between 18.6 and 24.9 indicates you are at a healthy"), dismissButton: .default(Text("OK")))
            }
}

Answer 1

UPDATE 用于显示带有showTip 函数的解决方案：

struct ComplexAlertWith3Variables: View {

    @State var under = false
    @State var thin = false
    @State var healthy = false
    @State var stepFive: Float = 18.3 // I don't know how it changes. From somewhere. and it doesn't matter now

    private var messageText: String {
        return thin ? "A of less than 18.5 indicates you are thin" : "" // compute other variants
    }

    var body: some View {

        let needToShowAlert: Binding<Bool> = Binding<Bool>(
        get: { self.under || self.thin || self.healthy },
        set: { if $0 == false { self.under = $0; self.thin = $0; self.healthy = $0 } })

        return Text("Fire show tip function, because I don't know from where it fires in your code")
            .onTapGesture { self.showTip() } // fire your function. so you see, it doesn't matter from where you change variables
            .alert(isPresented: needToShowAlert) {
                Alert(title: Text("Results"), message: Text(self.messageText), dismissButton: .default(Text("OK")))
        }

    }

    // your function (makes it shorter to fit more lines of code)
    func showTip() {
        if (stepFive <= Float(18)) { under = true } 
        else if (stepFive >= Float(18) && stepFive <= Float(18.5)) { thin = true }
        else if (stepFive >= 18.6) && (stepFive <= 24.9) { healthy = true }
    }
}

点击文本时的结果或会从其他地方触发功能：

我对此进行了一些尝试，我想我可以为您提供一个解决方案。关于making custom Binding variable 并在body 中使用它。除了在第一个变体中，我使用enum 编写了决策，但您也可以在代码 sn-p 中找到具有 3 个变量的解决方案：

struct ComplexAlert: View {

    @State private var option: SomeOption = .unselected

    var body: some View {
        // DISCLAIMER: I wrote in a such a way to fit more lines of code on the page
        // the main here is an idea, not code style =)
        let needToShowAlert: Binding<Bool> = Binding<Bool>(
            get: { self.option != .unselected },
            set: { if $0 == false { self.option = .unselected } })

        return VStack {
            Button(action: { self.option = .under }) { Text("make under") }
            Button(action: { self.option = .thin }) { Text("make thin") }
            Button(action: { self.option = .healthy }) { Text("make healthy") }
        }
            .alert(isPresented: needToShowAlert) {
                Alert(title: Text("Results"), message: Text(self.option.getAlertMessage()), dismissButton: .default(Text("OK")))
        }
    }
}

// MARK: if you need to use 3 variables:
struct ComplexAlertWith3Variables: View {

    @State var under = false
    @State var thin = false
    @State var healthy = false

    private var messageText: String {
        return under ? "under" : "" // compute other varianst
    }

    var body: some View {

        let needToShowAlert: Binding<Bool> = Binding<Bool>(
        get: { self.under || self.thin || self.healthy },
        set: { if $0 == false { self.under = $0; self.thin = $0; self.healthy = $0 } })

        return Text("Hello")
            .onTapGesture { self.under = true }
            .alert(isPresented: needToShowAlert) {
                Alert(title: Text("Results"), message: Text(self.messageText), dismissButton: .default(Text("OK")))
        }

    }
}

// MARK: enum which was used in the first solution:
enum SomeOption {

    case unselected
    case under
    case thin
    case healthy

    func getAlertMessage() -> String {
        switch self {
        case .unselected:
            return ""
        case .under:
            return "A of less than 18 means you are under weight. "
        case .thin:
            return "A of less than 18.5 indicates you are thin"
        case .healthy:
            return "A between 18.6 and 24.9 indicates you are at a healthy"
        }
    }

}

ComplexAlert 的结果将是：