Hai, I am at Day 47 making habit tracking app and I got stuck. I followed iExpense tutorial to parsing data between Views but I keep getting error. Do I miss something?

import Foundation

struct Activiy: Identifiable {
    var id = UUID()
    var title: String
    var description: String
}

import SwiftUI

class Activities: ObservableObject {
    @Published var listActivities = [Activiy]()

}

struct ContentView: View {
    @ObservedObject var activities = Activities()
    @State private var showingAddView = false

    var body: some View {
        NavigationView{
            List {
                ForEach(activities.listActivities) { item in
                    HStack{
                        VStack(alignment: .leading) {
                            Text(item.title)
                                .font(.headline)
                            Text(item.description)
                        }

                    }

                }
            }

            .navigationTitle("HabitTracking")
            .toolbar { // error => Generic parameter 'Content' could not be inferred
                ToolbarItem(placement: .navigationBarTrailing) {
                    Button(action: {
                        self.showingAddView = true
                    }, label: {
                        Image(systemName: "plus")
                    })
                }
            }

            .sheet(isPresented: $showingAddView, content: {
                ActivityForm(activities: self.activities)
            })

        }

    }

}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

import SwiftUI

struct ActivityForm: View {
    @Environment(\.presentationMode) var presentationMode

    @ObservedObject var activities = Activities // error => Type 'Activities.Type' cannot conform to 'ObservableObject'
    @State private var title = ""
    @State private var desc = ""

    var body: some View {
        NavigationView {
            Form {
                TextField("Title", text: $title)
                TextField("Description", text: $desc)
            }

            .navigationTitle("Add New Activity")
            .navigationBarItems(trailing:
                Button("Save"){
                    //action
                })
        }

    }
}

struct ActivityForm_Previews: PreviewProvider {
    static var previews: some View {
        ActivityForm(activities: Activities()) // error => Argument passed to call that takes no arguments
    }
}

Thank you for the help

Thank you @roosterboy , I didn't realize it.