SwiftUI Executing a method from a view after confirmation from the subview

Question

Is it technically possible to call a method from a view after getting the confirmation from the subview ? I could call it from the SubStruct if I pass the viewModel and item to it, but I am just curious about the code below which results in

Segmentation Fault: 11

import SwiftUI

struct ContentView: View {
    var body: some View {
        MainStruct(viewModel: MyViewModel())
    }
}

struct MainStruct: View {
    @StateObject var viewModel: MyViewModel
    @State var functionToPass: ()
    
    let items = ["test1", "test2", "test2"]
    
    var body: some View {
        ForEach(items, id: \.self) { (item) in
            Text(item).onTapGesture {
                functionToPass = viewModel.deleteItem(name: item)
            }
        }
        
        SubStruct(passedFunction: {functionToPass})
    }
    
    struct SubStruct: View {
        var passedFunction: () -> Void
        
        var body: some View {
            Button(action: {passedFunction()}, label: {
                Text("confirm deletion")
            })
        }
    }
    
}

class MyViewModel: ObservableObject {
    func deleteItem(name: String) {
        print(name)
        ///deletion logic
    }
}

Adrien · Accepted Answer · 2021-08-20 16:13:05Z

1

Try this :

struct MainStruct: View {
    @StateObject var viewModel: MyViewModel
    @State private var functionToPass: () -> Void = {}

    let items = ["test1", "test2", "test2"]

    var body: some View {
        VStack {
            ForEach(items, id: \.self) { item in
                Text(item)
                    .onTapGesture {
                        functionToPass = {
                            viewModel.deleteItem(name: item)
                        }
                    }
            }
            SubStruct(passedFunction: functionToPass)
        }
    }

    struct SubStruct: View {
        var passedFunction: () -> Void

        var body: some View {
            Button(action: {
                passedFunction()
            }, label: {
                Text("confirm deletion")
            })
        }
    }
}

answered Aug 20, 2021 at 16:13

Adrien

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2 Comments

hbr4u7vb2sljksdf2 Over a year ago

thanks, it is working ! could you explain briefly what the actual problem was ? wrong type in the @State var declaration ?

Adrien Over a year ago

You declared your functionToPass as Void and I guess you wanted a closure that takes no argument and returns Void so () -> Void. A State need an initial value, here an empty closure : {}. On tap gesture : you tried to assign the result of your function (Void) to your parameter. But you have to assign to it a closure that will execute your function (deleteItem). To SubStruct you can pass functionToPass directly as an argument (no need of {}). And you could do the same with Button : action: passedFunction

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