Cannot convert value of type 'Published<>.Publisher' to expected argument type 'Binding<>'

Question

I'm having a bit of a complicated construction and have trouble figuring out how to get it working:

class Parent : Codable, ObservableObject {
    @Published public var children: [Child]?

    public func getChildren(with name: String) -> [Child] {
        return children?.filter { $0.name == name } ?? []
    }
}

class Child : Codable, Hashable, ObservableObject {
    static func == (lhs: Child, rhs: Child) -> Bool {
        return lhs.name == rhs.name && lhs.isSomething == rhs.isSomething
    }

    func hash(into hasher: inout Hasher) {
        hasher.combine(name)
        hasher.combine(isSomething)
    }

    let name: String
    @Published var isSomething: Bool
}

...

struct MyView : View {
    @ObservedObject var parent: Parent
    var names: [String]

    var body: some View {
        ForEach(names, id: \.self) { name in

            ...

            ForEach(parent.getChildren(with: name), id: \.self) { child in
                Toggle(isOn: child.$isSomething) { <== ERROR HERE
                    ...
                }
            }
        }
    }
}

I had also tried Toggle(isOn: $child.isSomething) which of course leads to Cannot find '$child' in scope.

How do I resolve this? In more detail: How do I return the correct type from getChildren() that allows $child.isSomething for example?

(BTW, I used this to allow an ObservableObject class to be Codable. Although this seems unrelated, I've let this into my code extraction above because perhaps it matters.)

Reopened the question since the duplicate didn't solve the problem. — Joakim Danielson, Oct 23 '22 at 11:16
` $child.isSomething` - you can use this way if you bind with some another published variable that updates automatically based on the children's name (you can achieve this using combine framework) — YodagamaHeshan, Oct 24 '22 at 06:45

score -1 · Answer 1 · answered Oct 24 '22 at 07:29

We can use separate @Published property with .onChange .

struct ContentView: View {
    @ObservedObject var parent: Parent
    @State var names: [String] = ["test1", "test2"]
    
    var body: some View {
        ForEach(names, id: \.self) { name in
            
            GroupBox { // just added for the clarity
                ForEach($parent.filteredChildren) { $child in
                    Toggle(isOn: $child.isSomething) {
                        Text(child.name)
                    }
                }
            }
        }
        .onChange(of: names) { newValue in
            parent.updateChildren(with: "test") //<- here
        }
        .onAppear{
            names.append("test3")
        }
        
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView(parent: Parent(children:[ Child(name: "test"), Child(name: "test2")]))
    }
}

class Parent: ObservableObject {
    init(children: [Child]) {
        self.children = children
    }
    @Published public var children: [Child]
    @Published public var filteredChildren: [Child] = []
    
    func updateChildren(with name: String) {
        filteredChildren = children.filter { $0.name == name }
    }
}

class Child: ObservableObject, Identifiable {
    init(name: String) {
        self.name = name
    }
    let id = UUID().uuidString
    let name: String
    @Published var isSomething: Bool = false
}

Cannot convert value of type 'Published<>.Publisher' to expected argument type 'Binding<>'

1 Answers1