Using onAppear on ForEach-CodePudding

I created View which contains List and under List is Section:

struct SwiftUIView: View {
var body: some View {
    List {
        Section {
            EmptyView()
        } header: {
            Text("Some header text")
        }
        
        NewView()
    }
}
}

NewView and SomeViewModel code:

class SomeViewModel: ObservableObject {
    @Published var data: [String] = []

    func onAppear(){
        data = ["One", "Two", "Three"]
    }
}

struct NewView: View {

     @State private var viewModel = SomeViewModel()

     var body: some View {
        ForEach(viewModel.data, id: \.self){
                Text($0)
            }
            .onAppear(perform: viewModel.onAppear)
    }
}

Problem here is that onAppear modifier is not called on ForEach. When I added Text and use onAppear modifier on it, then it is working, but I don't need one more View. I tried to use EmptyView also, but again, onAppear is not called. Is there any way to call modifiers on ForEach?

CodePudding user response：

Try this approach to call onAppear()

struct ContentView: View {
    var body: some View {
        NewView()
    }
}

class SomeViewModel: ObservableObject {
    @Published var data: [String] = []
    
    func onAppear() {
        data = ["One", "Two", "Three"]
        print("----> in SomeViewModel onAppear")
    }
}

struct NewView: View {
    @StateObject var viewModel = SomeViewModel() // <-- here
    
    var body: some View {
        ForEach(viewModel.data, id: \.self){
            Text($0)
        }
        .onAppear{
            viewModel.onAppear()  // <-- here
        }
    }
}

CodePudding user response：

I think you should use init instead of onAppear to init the model

class SomeViewModel: ObservableObject {
    @Published var data: [String] = []

    init() {
        data = ["One", "Two", "Three"]
    }
}

struct NewView: View {

     @State private var viewModel = SomeViewModel()

     var body: some View {
        ForEach(viewModel.data, id: \.self){
                Text($0)
        }
    }
}