hi, im doing Day 47 Challenge but i have a problem. When i save new activity it wont append to [Activity] on main screen.

//
//  ContentView.swift
//  Learner
//
//  Created by Filip Pokłosiewicz on 31/10/2023.
//

import SwiftUI

struct ContentView: View {

    @State private var showingSheet = false

    @State private var activities: [Activity] = [
        Activity(title: "Nauka języka", description: "Codzienne ćwiczenia słownictwa."),
        Activity(title: "Ćwiczenia fizyczne", description: "Bieganie, rower, siłownia"),
        Activity(title: "Nauka programowania", description: "Swift lub SwiftUI")
    ]

    var body: some View {
        NavigationView {
            List(activities) { activity in
                VStack(alignment: .leading) {
                    Text(activity.title)
                        .font(.headline)
                    Text(activity.description)
                        .font(.subheadline)
                }
            }
            .navigationTitle("Activities")
            .toolbar {
                Button {
                    showingSheet = true

                } label: {
                    Image(systemName: "plus")
                }
            }
            .sheet(isPresented: $showingSheet) {
                AddActivity(activities: Activities())
            }
        }
    }
}

#Preview {
    ContentView()
}

//
//  AddActivity.swift
//  Learner
//
//  Created by Filip Pokłosiewicz on 03/11/2023.
//

import SwiftUI

struct AddActivity: View {

    @ObservedObject var activities: Activities

    @State private var title = ""
    @State private var description = ""
    @Environment(\.dismiss) var dismiss

    var body: some View {
        NavigationView {
            Form {
                TextField("Title", text: $title)
                TextField("Description", text: $description)
                    .padding(.bottom, 200)
            } .navigationTitle("Add your activity")
                .toolbar {
                    Button("Save") {
                        let item = Activity(title: title, description: description)
                        activities.items.append(item)
                        dismiss()
                    }
                }
        }
    }
}

#Preview {
    AddActivity(activities: Activities())
}

import Foundation

class Activities: ObservableObject {
    @Published var items = [Activity]()
}

//
//  ActivityItem.swift
//  Learner
//
//  Created by Filip Pokłosiewicz on 31/10/2023.
//

import Foundation

struct Activity: Identifiable {

    var id = UUID()
    var title: String
    var description: String

}

Because when you activities.items.append(item) it adding it to the items array in the class Activities. Also make a NEW instance of Activities So need to do a few changes.

1. Change

   @State private var activities: [Activity] = [
     Activity(title: "Nauka języka", description: "Codzienne ćwiczenia słownictwa."),
     Activity(title: "Ćwiczenia fizyczne", description: "Bieganie, rower, siłownia"),
     Activity(title: "Nauka programowania", description: "Swift lub SwiftUI")
   ]

   to

   @StateObject private var activities = Activities()

   Change

   .sheet(isPresented: $showingSheet) {
   AddActivity(activities: Activities())
   }

   to

   .sheet(isPresented: $showingSheet) {
   AddActivity(activities: activities)
   }

   if you want the orginal array of items change class Activities to

   class Activities: ObservableObject {
   @Published var items = [
               Activity(title: "Nauka języka", description: "Codzienne ćwiczenia słownictwa."),
               Activity(title: "Ćwiczenia fizyczne", description: "Bieganie, rower, siłownia"),
               Activity(title: "Nauka programowania", description: "Swift lub SwiftUI")
           ]
   }