结果值以'？ ：'表达式的类型“ some View”和“ ...”不匹配

Question

当我尝试使navigationBarItems三元以具有各种视图时出现此错误：

  

“？”中的结果值：'表达式的类型“ some View”和“ ProfileImageBarButton”不匹配

@State var searchTapped: Bool = false

var body: some View {
    NavigationView {
        Text("lol")

   --> here i get the error .navigationBarItems(leading: searchTapped ? backButton : ProfileImageBarButton(showMenu: $showMenu))
        .navigationBarTitle(Text(""), displayMode: .inline)
    }.overlay(searchTextField)
}

private var backButton: some View {
    Image(systemName: "arrow.left")
        .foregroundColor(Color.blue)
        .onTapGesture {
            self.searchTapped = false
        }
}

这是ProfileImageBarButton：

struct ProfileImageBarButton: View {
@Binding var showMenu: Bool

var body: some View {
    Image(uiImage: UserDefaults.standard.getProfileImage()!)
        .resizable()
        .renderingMode(.original)
        .frame(width: 30, height: 30)
        .clipShape(Circle())
        .onTapGesture {
            self.showMenu.toggle()
        }
}

}

Answer 1

错误是用表达式告诉您的：

condition ? true_result : false_result

true_result和false_result都必须具有相同的类型。

有多种方法可以解决此问题，这里有两种：

.navigationBarItems(leading: searchTapped ? AnyView(backButton) : AnyView(ProfileImageBarButton(showMenu: $showMenu)))

或

.navigationBarItems(leading: barItems())

...

func barItems() -> some View {
    return Group {
        if searchTapped {
            backButton
        } else {
            ProfileImageBarButton(showMenu: $showMenu)
        }
    }
}

Answer 2

您还可以使用@ViewBuilder来允许在其正文中放置不同的视图：

.navigationBarItems(leading: barItems)

@ViewBuilder
var barItems: some View {
    if searchTapped {
        backButton
    } else {
        ProfileImageBarButton(showMenu: $showMenu)
    }
}