SwiftUI: UI Declarative iOS

# SwiftUI memerlukan:
# 1. Xcode 11+ (untuk SwiftUI 1.0) atau Xcode 15+ (untuk fitur terbaru)
# 2. macOS Catalina 10.15+ atau lebih baru
# 3. iOS 13+ sebagai deployment target

# Membuat proyek baru di Xcode:
# 1. Buka Xcode → File → New → Project
# 2. Pilih "iOS" → "App"
# 3. Pastikan "Interface" dipilih: SwiftUI
# 4. Pastikan "Language" dipilih: Swift
# 5. Klik "Next" dan tentukan nama proyek

# Atau menggunakan Swift Package Manager untuk library:
# File → Add Package Dependencies
# Contoh: https://github.com/Alamofire/Alamofire

import SwiftUI

// ===== VIEW DASAR SWIFTUI =====

// Text — Menampilkan teks
Text("Halo, SwiftUI!")
    .font(.title)
    .fontWeight(.bold)
    .foregroundColor(.blue)
    .multilineTextAlignment(.center)

// Image — Menampilkan gambar
Image(systemName: "star.fill")        // SF Symbol
    .resizable()
    .aspectRatio(contentMode: .fit)
    .frame(width: 50, height: 50)
    .foregroundColor(.yellow)

Image("photo")                        // Asset catalog
    .resizable()
    .scaledToFit()
    .cornerRadius(12)

// Button — Tombol interaktif
Button(action: {
    print("Tombol ditekan!")
}) {
    HStack {
        Image(systemName: "hand.thumbsup.fill")
        Text("Suka")
    }
    .padding()
    .background(Color.blue)
    .foregroundColor(.white)
    .cornerRadius(10)
}

// Label — Ikon + Teks
Label("Beranda", systemImage: "house.fill")
    .font(.headline)

// Divider — Garis pemisah
Divider()
    .padding(.horizontal)

// Spacer — Mengisi ruang kosong
HStack {
    Text("Kiri")
    Spacer()
    Text("Kanan")
}

// Color — Bidang warna
Color.red
    .frame(width: 100, height: 100)
    .cornerRadius(16)

// Membuat custom view dengan protocol View
struct ProfileCard: View {
    let nama: String
    let jabatan: String
    let imageName: String

    var body: some View {
        VStack(spacing: 12) {
            Image(imageName)
                .resizable()
                .scaledToFill()
                .frame(width: 80, height: 80)
                .clipShape(Circle())
                .overlay(
                    Circle().stroke(Color.blue, lineWidth: 3)
                )

            Text(nama)
                .font(.title2)
                .fontWeight(.semibold)

            Text(jabatan)
                .font(.subheadline)
                .foregroundColor(.secondary)
        }
        .padding()
        .background(
            RoundedRectangle(cornerRadius: 16)
                .fill(Color(.systemBackground))
                .shadow(color: .black.opacity(0.1), radius: 8, y: 4)
        )
    }
}

// Menggunakan custom view
struct ContentView: View {
    var body: some View {
        VStack(spacing: 20) {
            ProfileCard(
                nama: "Budi Santoso",
                jabatan: "iOS Developer",
                imageName: "profile_budi"
            )
            ProfileCard(
                nama: "Ani Wijaya",
                jabatan: "UI/UX Designer",
                imageName: "profile_ani"
            )
        }
        .padding()
    }
}

import SwiftUI

struct StackExamples: View {
    var body: some View {
        ScrollView {
            VStack(spacing: 24) {

                // VStack — Vertikal stack
                VStack(alignment: .leading, spacing: 8) {
                    Text("VStack Example")
                        .font(.headline)
                    Text("Item 1")
                    Text("Item 2")
                    Text("Item 3")
                }
                .padding()
                .background(Color.blue.opacity(0.1))
                .cornerRadius(12)

                // HStack — Horizontal stack
                HStack(spacing: 16) {
                    Image(systemName: "star.fill")
                        .foregroundColor(.yellow)
                    Text("Rating: 4.8")
                        .font(.subheadline)
                    Spacer()
                    Text("128 ulasan")
                        .font(.caption)
                        .foregroundColor(.secondary)
                }
                .padding()
                .background(Color.green.opacity(0.1))
                .cornerRadius(12)

                // ZStack — Layered stack (tumpuk)
                ZStack {
                    RoundedRectangle(cornerRadius: 16)
                        .fill(
                            LinearGradient(
                                colors: [.purple, .blue],
                                startPoint: .topLeading,
                                endPoint: .bottomTrailing
                            )
                        )
                        .frame(height: 150)

                    VStack {
                        Image(systemName: "bolt.fill")
                            .font(.largeTitle)
                            .foregroundColor(.white)
                        Text("Premium Feature")
                            .font(.title3)
                            .fontWeight(.bold)
                            .foregroundColor(.white)
                    }
                }

                // Grid — LazyVGrid untuk grid layout
                let columns = [
                    GridItem(.flexible()),
                    GridItem(.flexible()),
                    GridItem(.flexible())
                ]

                LazyVGrid(columns: columns, spacing: 16) {
                    ForEach(1...9, id: \.self) { index in
                        RoundedRectangle(cornerRadius: 12)
                            .fill(Color.orange.opacity(0.3))
                            .frame(height: 80)
                            .overlay(
                                Text("\(index)")
                                    .font(.title2)
                                    .fontWeight(.bold)
                            )
                    }
                }
            }
            .padding()
        }
    }
}

import SwiftUI

struct ModifierOrderExample: View {
    var body: some View {
        VStack(spacing: 30) {

            // Contoh 1: Background SEBELUM padding
            // → Background hanya selebar teks
            Text("Contoh 1")
                .background(Color.blue)
                .padding()

            // Contoh 2: Background SETELAH padding
            // → Background mencakup area padding
            Text("Contoh 2")
                .padding()
                .background(Color.green)

            // Contoh 3: Corner radius sebelum shadow
            Text("Contoh 3")
                .padding()
                .background(Color.orange)
                .cornerRadius(12)
                .shadow(radius: 5)

            // Contoh 4: Urutan kompleks
            Text("SwiftUI!")
                .font(.title)
                .fontWeight(.bold)
                .foregroundColor(.white)
                .padding(.horizontal, 24)
                .padding(.vertical, 12)
                .background(
                    LinearGradient(
                        colors: [.purple, .blue],
                        startPoint: .leading,
                        endPoint: .trailing
                    )
                )
                .cornerRadius(25)
                .shadow(color: .purple.opacity(0.4), radius: 10, y: 5)
        }
    }
}

import SwiftUI

// Membuat custom modifier
struct CardModifier: ViewModifier {
    var backgroundColor: Color = Color(.systemBackground)
    var cornerRadius: CGFloat = 16

    func body(content: Content) -> some View {
        content
            .padding()
            .background(backgroundColor)
            .cornerRadius(cornerRadius)
            .shadow(color: .black.opacity(0.1), radius: 8, y: 4)
    }
}

// Modifier untuk gradient header
struct GradientHeaderModifier: ViewModifier {
    func body(content: Content) -> some View {
        content
            .font(.largeTitle)
            .fontWeight(.bold)
            .foregroundColor(.white)
            .frame(maxWidth: .infinity)
            .padding(.vertical, 20)
            .background(
                LinearGradient(
                    colors: [.blue, .purple],
                    startPoint: .topLeading,
                    endPoint: .bottomTrailing
                )
            )
    }
}

// Extension untuk kemudahan penggunaan
extension View {
    func cardStyle(
        backgroundColor: Color = Color(.systemBackground),
        cornerRadius: CGFloat = 16
    ) -> some View {
        modifier(CardModifier(
            backgroundColor: backgroundColor,
            cornerRadius: cornerRadius
        ))
    }

    func gradientHeader() -> some View {
        modifier(GradientHeaderModifier())
    }
}

// Menggunakan custom modifier
struct ModifierDemoView: View {
    var body: some View {
        VStack(spacing: 20) {
            Text("Selamat Datang!")
                .gradientHeader()

            Text("Ini adalah kartu dengan custom modifier")
                .cardStyle()

            Text("Kartu dengan warna berbeda")
                .cardStyle(
                    backgroundColor: .blue.opacity(0.1),
                    cornerRadius: 20
                )
        }
    }
}

import SwiftUI

// @State — State lokal milik view
struct CounterView: View {
    @State private var count = 0

    var body: some View {
        VStack(spacing: 20) {
            Text("Hitungan: \(count)")
                .font(.title)
                .fontWeight(.bold)

            HStack(spacing: 20) {
                Button("−") {
                    if count > 0 { count -= 1 }
                }
                .font(.title)
                .frame(width: 60, height: 60)
                .background(Color.red)
                .foregroundColor(.white)
                .cornerRadius(30)

                Button("+") {
                    count += 1
                }
                .font(.title)
                .frame(width: 60, height: 60)
                .background(Color.green)
                .foregroundColor(.white)
                .cornerRadius(30)
            }
        }
    }
}

// @Binding — Referensi ke state parent
struct ToggleCard: View {
    @Binding var isOn: Bool
    let title: String

    var body: some View {
        HStack {
            Image(systemName: isOn ? "checkmark.circle.fill" : "circle")
                .foregroundColor(isOn ? .green : .gray)
                .font(.title2)

            Text(title)
                .font(.body)

            Spacer()

            Toggle("", isOn: $isOn)
                .labelsHidden()
        }
        .padding()
        .background(Color(.secondarySystemBackground))
        .cornerRadius(12)
    }
}

// Parent view menggunakan @Binding
struct SettingsView: View {
    @State private var notificationsOn = true
    @State private var darkModeOn = false
    @State private var autoSyncOn = true

    var body: some View {
        VStack(spacing: 12) {
            Text("Pengaturan")
                .font(.title)
                .fontWeight(.bold)

            ToggleCard(isOn: $notificationsOn, title: "Notifikasi")
            ToggleCard(isOn: $darkModeOn, title: "Mode Gelap")
            ToggleCard(isOn: $autoSyncOn, title: "Sinkronisasi Otomatis")
        }
        .padding()
    }
}

import SwiftUI
import Combine

// ObservableObject — Shared state untuk beberapa view
class UserViewModel: ObservableObject {
    @Published var nama: String = ""
    @Published var email: String = ""
    @Published var isLoggedIn: Bool = false
    @Published var isLoading: Bool = false

    func login(email: String, password: String) {
        isLoading = true
        // Simulasi API call
        DispatchQueue.main.asyncAfter(deadline: .now() + 2) {
            self.email = email
            self.nama = "Budi Santoso"
            self.isLoggedIn = true
            self.isLoading = false
        }
    }

    func logout() {
        nama = ""
        email = ""
        isLoggedIn = false
    }
}

// @StateObject — Membuat dan memiliki ViewModel
struct LoginView: View {
    @StateObject private var viewModel = UserViewModel()

    var body: some View {
        Group {
            if viewModel.isLoggedIn {
                ProfileView()
            } else {
                LoginFormView()
            }
        }
        .environmentObject(viewModel)  // Inject ke environment
    }
}

struct LoginFormView: View {
    @EnvironmentObject var viewModel: UserViewModel
    @State private var email = ""
    @State private var password = ""

    var body: some View {
        VStack(spacing: 16) {
            Text("Masuk")
                .font(.largeTitle)
                .fontWeight(.bold)

            TextField("Email", text: $email)
                .textFieldStyle(.roundedBorder)
                .keyboardType(.emailAddress)
                .autocapitalization(.none)

            SecureField("Password", text: $password)
                .textFieldStyle(.roundedBorder)

            Button(action: {
                viewModel.login(email: email, password: password)
            }) {
                if viewModel.isLoading {
                    ProgressView()
                        .progressViewStyle(CircularProgressViewStyle(tint: .white))
                } else {
                    Text("Masuk")
                        .fontWeight(.semibold)
                }
            }
            .frame(maxWidth: .infinity)
            .padding()
            .background(Color.blue)
            .foregroundColor(.white)
            .cornerRadius(12)
            .disabled(viewModel.isLoading)
        }
        .padding()
    }
}

// @EnvironmentObject — Mengakses shared state
struct ProfileView: View {
    @EnvironmentObject var viewModel: UserViewModel

    var body: some View {
        VStack(spacing: 16) {
            Image(systemName: "person.circle.fill")
                .font(.system(size: 80))
                .foregroundColor(.blue)

            Text(viewModel.nama)
                .font(.title)
                .fontWeight(.bold)

            Text(viewModel.email)
                .font(.subheadline)
                .foregroundColor(.secondary)

            Button("Keluar") {
                viewModel.logout()
            }
            .foregroundColor(.red)
        }
        .padding()
    }
}

// @Environment — System values
struct ThemeAwareView: View {
    @Environment(\.colorScheme) var colorScheme
    @Environment(\.horizontalSizeClass) var sizeClass

    var body: some View {
        VStack {
            Text(colorScheme == .dark ? "Mode Gelap" : "Mode Terang")
            Text(sizeClass == .compact ? "Compact" : "Regular")
        }
    }
}

import SwiftUI

// Model data
struct Mahasiswa: Identifiable {
    let id = UUID()
    let nama: String
    let jurusan: String
    let angkatan: Int
    let ipk: Double
}

// List dasar dengan ForEach
struct MahasiswaListView: View {
    let mahasiswa: [Mahasiswa] = [
        Mahasiswa(nama: "Budi Santoso", jurusan: "Teknik Informatika", angkatan: 2023, ipk: 3.8),
        Mahasiswa(nama: "Ani Wijaya", jurusan: "Sistem Informasi", angkatan: 2023, ipk: 3.9),
        Mahasiswa(nama: "Citra Dewi", jurusan: "Teknik Komputer", angkatan: 2024, ipk: 3.7),
        Mahasiswa(nama: "Dodi Pratama", jurusan: "Teknik Informatika", angkatan: 2022, ipk: 3.5),
        Mahasiswa(nama: "Eka Putri", jurusan: "Sistem Informasi", angkatan: 2024, ipk: 3.95),
    ]

    var body: some View {
        List(mahasiswa) { mhs in
            HStack(spacing: 12) {
                Circle()
                    .fill(Color.blue.gradient)
                    .frame(width: 44, height: 44)
                    .overlay(
                        Text(String(mhs.nama.prefix(1)))
                            .foregroundColor(.white)
                            .fontWeight(.bold)
                    )

                VStack(alignment: .leading, spacing: 4) {
                    Text(mhs.nama)
                        .font(.headline)
                    Text("\(mhs.jurusan) — Angkatan \(mhs.angkatan)")
                        .font(.caption)
                        .foregroundColor(.secondary)
                }

                Spacer()

                VStack(alignment: .trailing) {
                    Text(String(format: "%.2f", mhs.ipk))
                        .font(.title3)
                        .fontWeight(.bold)
                        .foregroundColor(mhs.ipk >= 3.7 ? .green : .orange)
                    Text("IPK")
                        .font(.caption2)
                        .foregroundColor(.secondary)
                }
            }
            .padding(.vertical, 4)
        }
        .listStyle(.insetGrouped)
        .navigationTitle("Daftar Mahasiswa")
    }
}

import SwiftUI

struct TodoItem: Identifiable {
    let id = UUID()
    var title: String
    var isCompleted: Bool
    var priority: Priority

    enum Priority: String, CaseIterable {
        case tinggi = "🔴 Tinggi"
        case sedang = "🟡 Sedang"
        case rendah = "🟢 Rendah"
    }
}

struct TodoListView: View {
    @State private var todos = [
        TodoItem(title: "Belajar SwiftUI", isCompleted: true, priority: .tinggi),
        TodoItem(title: "Buat prototipe UI", isCompleted: false, priority: .tinggi),
        TodoItem(title: "Review pull request", isCompleted: false, priority: .sedang),
        TodoItem(title: "Update dokumentasi", isCompleted: true, priority: .rendah),
        TodoItem(title: "Deploy ke TestFlight", isCompleted: false, priority: .sedang),
    ]

    @State private var showAddSheet = false

    var completedTodos: [TodoItem] { todos.filter { $0.isCompleted } }
    var pendingTodos: [TodoItem] { todos.filter { !$0.isCompleted } }

    var body: some View {
        List {
            // Section belum selesai
            Section("Belum Selesai (\(pendingTodos.count))") {
                ForEach(pendingTodos) { todo in
                    todoRow(todo)
                }
                .onDelete { indexSet in
                    // Handle delete
                }
            }

            // Section sudah selesai
            if !completedTodos.isEmpty {
                Section("Selesai (\(completedTodos.count))") {
                    ForEach(completedTodos) { todo in
                        todoRow(todo)
                    }
                }
            }
        }
        .listStyle(.insetGrouped)
        .navigationTitle("Todo List")
        .toolbar {
            ToolbarItem(placement: .navigationBarTrailing) {
                Button(action: { showAddSheet = true }) {
                    Image(systemName: "plus")
                }
            }
        }
        .sheet(isPresented: $showAddSheet) {
            AddTodoSheet(todos: $todos)
        }
    }

    func todoRow(_ todo: TodoItem) -> some View {
        HStack {
            Image(systemName: todo.isCompleted ?
                  "checkmark.circle.fill" : "circle")
                .foregroundColor(todo.isCompleted ? .green : .gray)
                .onTapGesture {
                    if let idx = todos.firstIndex(where: { $0.id == todo.id }) {
                        todos[idx].isCompleted.toggle()
                    }
                }

            VStack(alignment: .leading) {
                Text(todo.title)
                    .strikethrough(todo.isCompleted)
                Text(todo.priority.rawValue)
                    .font(.caption)
            }
        }
        .swipeActions(edge: .trailing) {
            Button(role: .destructive) {
                todos.removeAll { $0.id == todo.id }
            } label: {
                Label("Hapus", systemImage: "trash")
            }
        }
        .swipeActions(edge: .leading) {
            Button {
                if let idx = todos.firstIndex(where: { $0.id == todo.id }) {
                    todos[idx].isCompleted.toggle()
                }
            } label: {
                Label("Selesai", systemImage: "checkmark")
            }
            .tint(.green)
        }
    }
}

import SwiftUI

// Model untuk navigasi
struct Produk: Identifiable, Hashable {
    let id = UUID()
    let nama: String
    let harga: Int
    let deskripsi: String
    let kategori: String
}

// Navigation Stack dengan programmatic navigation
struct TokoApp: View {
    @State private var path = NavigationPath()
    @State private var selectedKategori: String?

    let produkList = [
        Produk(nama: "iPhone 16 Pro", harga: 18999000, deskripsi: "Flagship Apple terbaru", kategori: "Smartphone"),
        Produk(nama: "MacBook Air M3", harga: 16999000, deskripsi: "Laptop ultraportable", kategori: "Laptop"),
        Produk(nama: "iPad Pro M4", harga: 14999000, deskripsi: "Tablet profesional", kategori: "Tablet"),
        Produk(nama: "AirPods Pro 3", harga: 3999000, deskripsi: "Earbuds premium", kategori: "Audio"),
        Produk(nama: "Apple Watch Ultra 3", harga: 12999000, deskripsi: "Smartwatch outdoor", kategori: "Wearable"),
    ]

    var body: some View {
        NavigationStack(path: $path) {
            List {
                // NavigationLink sederhana
                Section("Kategori") {
                    ForEach(["Smartphone", "Laptop", "Tablet", "Audio", "Wearable"], id: \.self) { kategori in
                        NavigationLink(value: kategori) {
                            Label(kategori, systemImage: iconForKategori(kategori))
                        }
                    }
                }

                // NavigationLink ke detail
                Section("Produk Populer") {
                    ForEach(produkList) { produk in
                        NavigationLink(value: produk) {
                            HStack {
                                VStack(alignment: .leading) {
                                    Text(produk.nama)
                                        .font(.headline)
                                    Text("Rp \(produk.harga.formatted())")
                                        .font(.subheadline)
                                        .foregroundColor(.blue)
                                }
                            }
                        }
                    }
                }
            }
            .navigationTitle("Toko Online")
            .navigationDestination(for: String.self) { kategori in
                KategoriView(
                    kategori: kategori,
                    produk: produkList.filter { $0.kategori == kategori }
                )
            }
            .navigationDestination(for: Produk.self) { produk in
                DetailProdukView(produk: produk, path: $path)
            }
        }
    }

    func iconForKategori(_ kategori: String) -> String {
        switch kategori {
        case "Smartphone": return "iphone"
        case "Laptop": return "laptopcomputer"
        case "Tablet": return "ipad"
        case "Audio": return "airpodspro"
        case "Wearable": return "applewatch"
        default: return "bag"
        }
    }
}

struct KategoriView: View {
    let kategori: String
    let produk: [Produk]

    var body: some View {
        List(produk) { item in
            NavigationLink(value: item) {
                HStack {
                    RoundedRectangle(cornerRadius: 8)
                        .fill(Color.blue.opacity(0.2))
                        .frame(width: 50, height: 50)
                        .overlay(Image(systemName: "bag.fill"))

                    VStack(alignment: .leading) {
                        Text(item.nama)
                            .font(.headline)
                        Text("Rp \(item.harga.formatted())")
                            .foregroundColor(.blue)
                    }
                }
            }
        }
        .navigationTitle(kategori)
    }
}

struct DetailProdukView: View {
    let produk: Produk
    @Binding var path: NavigationPath

    var body: some View {
        ScrollView {
            VStack(alignment: .leading, spacing: 16) {
                RoundedRectangle(cornerRadius: 16)
                    .fill(Color.blue.opacity(0.2))
                    .frame(height: 250)
                    .overlay(
                        Image(systemName: "bag.fill")
                            .font(.system(size: 60))
                            .foregroundColor(.blue)
                    )

                Text(produk.nama)
                    .font(.title)
                    .fontWeight(.bold)

                Text("Rp \(produk.harga.formatted())")
                    .font(.title2)
                    .foregroundColor(.blue)
                    .fontWeight(.semibold)

                Text(produk.deskripsi)
                    .font(.body)
                    .foregroundColor(.secondary)

                Button("Beli Sekarang") {}
                    .buttonStyle(.borderedProminent)
                    .controlSize(.large)
                    .frame(maxWidth: .infinity)

                Button("Kembali ke Beranda") {
                    path = NavigationPath()  // Pop semua
                }
                .frame(maxWidth: .infinity)
            }
            .padding()
        }
        .navigationTitle("Detail")
        .navigationBarTitleDisplayMode(.inline)
    }
}

import SwiftUI

struct MainTabView: View {
    @State private var selectedTab = 0

    var body: some View {
        TabView(selection: $selectedTab) {
            TokoApp()
                .tabItem {
                    Label("Beranda", systemImage: "house.fill")
                }
                .tag(0)

            Text("Pencarian")
                .tabItem {
                    Label("Cari", systemImage: "magnifyingglass")
                }
                .tag(1)

            Text("Keranjang")
                .tabItem {
                    Label("Keranjang", systemImage: "cart.fill")
                }
                .badge(3)  // Badge notification
                .tag(2)

            Text("Profil")
                .tabItem {
                    Label("Profil", systemImage: "person.fill")
                }
                .tag(3)
        }
    }
}

import SwiftUI

struct RegistrationForm: View {
    @State private var nama = ""
    @State private var email = ""
    @State private var password = ""
    @State private var confirmPassword = ""
    @State private var tanggalLahir = Date()
    @State private var jenisKelamin = 0
    @State private var agreedToTerms = false
    @State private var selectedInterests: Set = []

    let interests = ["iOS", "Android", "Web", "Machine Learning", "DevOps"]

    var isFormValid: Bool {
        !nama.isEmpty &&
        !email.isEmpty &&
        email.contains("@") &&
        password.count >= 8 &&
        password == confirmPassword &&
        agreedToTerms
    }

    var body: some View {
        Form {
            // Section Informasi Dasar
            Section("Informasi Dasar") {
                TextField("Nama Lengkap", text: $nama)
                    .textContentType(.name)

                TextField("Email", text: $email)
                    .textContentType(.emailAddress)
                    .keyboardType(.emailAddress)
                    .autocapitalization(.none)

                SecureField("Password (min 8 karakter)", text: $password)
                SecureField("Konfirmasi Password", text: $confirmPassword)

                if !password.isEmpty && password == confirmPassword {
                    Label("Password cocok", systemImage: "checkmark.circle.fill")
                        .font(.caption)
                        .foregroundColor(.green)
                } else if !confirmPassword.isEmpty {
                    Label("Password tidak cocok", systemImage: "xmark.circle.fill")
                        .font(.caption)
                        .foregroundColor(.red)
                }
            }

            // Section Info Tambahan
            Section("Informasi Tambahan") {
                DatePicker("Tanggal Lahir",
                          selection: $tanggalLahir,
                          displayedComponents: .date)

                Picker("Jenis Kelamin", selection: $jenisKelamin) {
                    Text("Laki-laki").tag(0)
                    Text("Perempuan").tag(1)
                    Text("Lainnya").tag(2)
                }
                .pickerStyle(.segmented)
            }

            // Section Minat
            Section("Minat Teknologi") {
                ForEach(interests, id: \.self) { interest in
                    Button(action: {
                        if selectedInterests.contains(interest) {
                            selectedInterests.remove(interest)
                        } else {
                            selectedInterests.insert(interest)
                        }
                    }) {
                        HStack {
                            Text(interest)
                            Spacer()
                            if selectedInterests.contains(interest) {
                                Image(systemName: "checkmark.circle.fill")
                                    .foregroundColor(.blue)
                            }
                        }
                    }
                    .foregroundColor(.primary)
                }
            }

            // Section Persetujuan
            Section {
                Toggle("Saya menyetujui syarat & ketentuan", isOn: $agreedToTerms)
            }

            // Submit Button
            Section {
                Button(action: {
                    print("Form submitted!")
                }) {
                    Text("Daftar Sekarang")
                        .frame(maxWidth: .infinity)
                        .fontWeight(.semibold)
                }
                .disabled(!isFormValid)
            }
        }
        .navigationTitle("Registrasi")
    }
}

import SwiftUI

// Contoh preview yang baik
struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        Group {
            // Preview mode terang
            MahasiswaListView()
                .previewDisplayName("Light Mode")

            // Preview mode gelap
            MahasiswaListView()
                .preferredColorScheme(.dark)
                .previewDisplayName("Dark Mode")

            // Preview ukuran kecil (iPhone SE)
            MahasiswaListView()
                .previewDevice("iPhone SE (3rd generation)")
                .previewDisplayName("iPhone SE")
        }
    }
}

// Di SwiftUI terbaru (iOS 17+), gunakan #Preview macro
#Preview("Mahasiswa List") {
    NavigationStack {
        MahasiswaListView()
    }
}

#Preview("Dark Mode") {
    NavigationStack {
        MahasiswaListView()
    }
    .preferredColorScheme(.dark)
}