Preview crash with SwiftUI @Binding: communication with the app was interrupted

Question

So I have an XCode project that has 2 .swift files that shares a variable through SwiftUI's @Binding.

The project builds and run through the Simulator just fine.

But whenever I try to use Preview on the secondary file (which receives the variable from the main file), it crashes after succesfully built saying "MyProject.app crashed: communication with the app was interrupted".

I can still test the project by:

Using the Simulator
Previewing the main file (ContentView.swift) (Yes previewing the main file works fine)

But its really time consuming for building and testing since it takes several actions in my app to get to the view of the secondary file and everytime Xcode refresh the app restarts.

Here is my code for the sondary file:

import SwiftUI

struct Menu_Screen : View {
    @Binding var TapToBegin:Bool
    var body: some View {
        Button(action: {

        }) {
            Text("A Button").color(.white).frame(width: TapToBegin ? 50:0, height: TapToBegin ? 100:0).background(Color.blue).cornerRadius(10)
        }
    } }

#if DEBUG 
    struct Menu_Screen_Previews : PreviewProvider {
    @State static var BoolVariable = true
    static var previews: some View {
        Menu_Screen(TapToBegin: $BoolVariable)
    } }
#endif

I would like to use Preview with the secondary file so I can always stay on its view and save time. Any help would be very appreciated.

score 13 · Accepted Answer · edited Jul 24 '19 at 16:04

13

Replace

#if DEBUG 
    struct Menu_Screen_Previews : PreviewProvider {
    @State static var BoolVariable = true
    static var previews: some View {
        Menu_Screen(TapToBegin: $BoolVariable)
    } }
#endif

with

#if DEBUG 
    struct Menu_Screen_Previews : PreviewProvider {

    static var previews: some View {
        Menu_Screen(TapToBegin: .constant(true))
    } }
#endif

edited Jul 24 '19 at 16:04

Roman Podymov

4,168
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answered Jul 24 '19 at 15:56

Young40

156
4

Thanks! The previous answer solved it for me but this works too – Nguyễn Khắc Hào Jul 26 '19 at 17:28

score 2 · Answer 2 · answered Jul 17 '19 at 09:03

#if DEBUG
struct Menu_Screen_Previews : PreviewProvider {
    static var BoolVariable = true
    static let BoolVariableBinding = Binding(getValue: { BoolVariable },
                                             setValue: { BoolVariable = $0 })
    static var previews: some View {
        Menu_Screen(TapToBegin: BoolVariableBinding)
    }
}
#endif

score 2 · Answer 3 · answered Oct 09 '19 at 22:46

The other answers led me in the right direction, but didn't solve the issue for me. I was getting the same error in Xcode, but the Binding I needed to send my View was not just a boolean value, but an array of structs. I'm posting my working code in the hope it helps others with this error.

struct StudentsView_Previews: PreviewProvider {
    static let prevStudents: [Student] = [
         Student(id: UUID().uuidString, firstName: "John", lastName: "Doe"),
         Student(id: UUID().uuidString, firstName: "Jane", lastName: "Doe"),
         Student(id: UUID().uuidString, firstName: "Sam", lastName: "Smith")
    ]
    static let prevStudentsBinding = Binding.constant(prevStudents)
    static let prevClassTitle = "Math 100"

    static var previews: some View {
        StudentsView(students: prevStudentsBinding, classTitle: prevClassTitle)
    }
}

struct Students: View {
    @Binding var students: [Student]
    let classTitle: String

    var body: some View {
        List(students.indices) { idx in
            Text(self.students[idx].fullName())
        }       
    }.navigationBarTitle(classTitle)
}

struct Student : Identifiable {
    var id: String
    var firstName: String
    var lastName: String
    func fullName() -> String {
        return firstName + " " + lastName
    }
}

Preview crash with SwiftUI @Binding: communication with the app was interrupted

3 Answers3