Switching Views with button do not work at all - ios

can someone please help me with this issue? I'm trying to detect the issue for like 2 hours now.
I want to switch view from LoginView() to RegistrationView() when button("Test") in LoginView() is pressed.
I did try this solution but it does nothing.
Any help is welcomed...
i have no idea how to change to registrationView()
struct mainView: View {
#State var show = false
var body: some View {
return Group {
if show {
RegistrationView()
}
}
}
}
struct LoginView : View {
#Binding var show: Bool
#StateObject private var loginVM = LoginViewModel()
var body: some View {
ZStack {BGimg()
if !loginVM.isAuthenticated {
VStack() {
.ignoresSafeArea(.all)
UsernameTextField(username: $loginVM.username)
PasswordSecureField(password: $loginVM.password)
ForgotPassword()
Button(action: loginVM.login) {
LoginButtonContent()
})
Button("Test") {
show.toggle()
}
}
.navigationBarHidden(false)
}
else if loginVM.isAuthenticated {
Home()
.navigationBarItems(trailing:
Button(action: loginVM.signout) {
Text("Sign out")
}
)
}
}
}
struct LoginView_Previews: PreviewProvider {
static var previews: some View {
LoginView()
.previewDevice("iPhone 12 Pro")
}
}

Related

Refresh List After a New Entity is Added in Core Data for SwiftUI App

I am building a small app using SwiftUI and Core Data. I have a main view, which launches the sheet. The sheet allows me to add a new movie to the SQLite database through Core Data. But I am having a hard time to refresh the parent view once the sheet is dismissed.
ContentView
struct ContentView: View {
#State private var isPresented: Bool = false
#StateObject private var vm = MovieListViewModel()
var body: some View {
NavigationView {
VStack {
List(vm.movies) { movie in
Text(movie.title)
}
}
.navigationTitle("Movies")
.toolbar(content: {
ToolbarItem(placement: .navigationBarTrailing) {
Button("Add Movie") {
isPresented = true
}
}
})
.sheet(isPresented: $isPresented, content: {
AddMovieView()
})
.onAppear {
try? vm.populateMovies()
}.padding()
}
}
}
AddMovieView
struct AddMovieView: View {
#Environment(\.dismiss) private var dismiss
#StateObject private var vm = AddMovieViewModel()
var body: some View {
Form {
TextField("Title", text: $vm.title)
Button("Save") {
do {
try vm.saveMovie()
dismiss()
} catch {
print(error.localizedDescription)
}
}
}
}
}
Do I need to call vm.populateMovies() on the onDismiss function of the sheet from the ContentView?
You can use a #FetchRequest as follows:
struct ContentView: View {
#FetchRequest(sortDescriptors: []) var movies: FetchedResults<Movie>
#State private var isPresented: Bool = false
#StateObject private var vm = MovieListViewModel()
var body: some View {
NavigationView {
VStack {
List(movies) { movie in
Text(movie.title)
}
}
.navigationTitle("Movies")
.toolbar(content: {
ToolbarItem(placement: .navigationBarTrailing) {
Button("Add Movie") {
isPresented = true
}
}
})
.sheet(isPresented: $isPresented, content: {
AddMovieView()
})
.padding()
}
}
}
You won't need a populateMovies() as the FetchRequest result is automatically populated.

How to properly implement a global variable in SwiftUI

I am going to create a SwiftUI application where I want to be able to swap between 3 modes. I am trying EnvironmentObject without success. I am able to change the view displayed locally, but from another View (in the end will be a class) I get a
fatal error: No ObservableObject of type DisplayView found. A View.environmentObject(_:) for DisplayView may be missing as an ancestor of this view.
Here is my code. The first line of the ContentView if/else fails.
enum ViewMode {
case Connect, Loading, ModeSelection
}
class DisplayView: ObservableObject {
#Published var displayMode: ViewMode = .Connect
}
struct ContentView: View {
#EnvironmentObject var viewMode: DisplayView
var body: some View {
VStack {
if viewMode.displayMode == .Connect {
ConnectView()
} else if viewMode.displayMode == .Loading {
LoadingView()
} else if viewMode.displayMode == .ModeSelection {
ModeSelectView()
} else {
Text("Error.")
}
TestView() //Want this to update the var & change UI.
}
.environmentObject(viewMode)
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
.environmentObject(DisplayView())
}
}
//FAILS
struct TestView: View {
#EnvironmentObject var showView: DisplayView
var body: some View {
HStack {
Button("-> load") {
self.showView.displayMode = .Loading
}
}
}
}
struct ConnectView: View {
var body: some View {
Text("Connect...")
}
}
struct LoadingView: View {
var body: some View {
Text("Loading...")
}
}
struct ModeSelectView: View {
var body: some View {
Text("Select Mode")
}
}
I would like to be able to update DisplayView from anywhere and have the ContentView UI adapt accordingly. I can update from within ContentView but I want to be able update from anywhere and have my view change.
I needed to inject BEFORE - so this fixed things up:
#main
struct fooApp: App {
var body: some Scene {
WindowGroup {
ContentView()
.environmentObject(DisplayView()) //super key!
}
}
}
I also tried a Singleton class to store some properties - and thus they are available from anywhere and can be updated anywhere - without having to declare EnvironmentObject. It's just another way that can work in different circumstances.
class PropContainerModel {
public var foo = "Hello"
static let shared = PropContainerModel()
private override init(){}
}
And then somewhere else
let thisFoo = PropContainerModel.shared.foo
//
PropContainerModel.shared.foo = "There"
Update here (Singleton but changes reflect in the SwiftUI UI).
class PropContainerModel: ObservableObject
{
#Published var foo: String = "Foo"
static let shared = PropContainerModel()
private init(){}
}
struct ContentView: View
{
#ObservedObject var propertyModel = PropContainerModel.shared
var body: some View {
VStack {
Text("foo = \(propertyModel.foo)")
.padding()
Button {
tapped(value: "Car")
} label: {
Image(systemName:"car")
.font(.system(size: 24))
.foregroundColor(.black)
}
Spacer()
.frame(height:20)
Button {
tapped(value: "Star")
} label: {
Image(systemName:"star")
.font(.system(size: 24))
.foregroundColor(.black)
}
}
}
func tapped(value: String)
{
PropContainerModel.shared.foo = value
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}

swiftui subview reappear after click the back button and update state data

Very strange behavior.
Click the back button on the subpage (Subview) to return to the main page (ContentView). However, the subpage (Subview) automatically opens again. Why?
import SwiftUI
struct ContentView: View {
#State var things: [String] = []
#State var count: Int = 0
var body: some View {
NavigationView{
List {
ForEach(things.indices, id: \.self) { index in
Text(things[index])
}
}
.onAppear {
update()
}
.navigationTitle("a")
.toolbar{
NavigationLink(destination: Subview(count: $count), label: {
Text("sub")
})
}
}
}
func update() {
things = []
for i in 0...count {
things.append(String(i))
}
}
}
struct Subview: View {
var count : Binding<Int>
var body: some View {
Text("sub")
.onAppear {
count.wrappedValue += 1
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
NavigationLink should always be inside a NavigationView. If you put it in the toolbar or some other place, you might run into weird issues.
Instead, use the init(destination:isActive:label:) initializer. Then set the presentingNextPage property to true when you want to present the next page.
struct ContentView: View {
#State var things: [String] = []
#State var count: Int = 0
#State var presentingNextPage = false
var body: some View {
NavigationView {
List {
ForEach(things.indices, id: \.self) { index in
Text(things[index])
}
/// placeholder navigation link
NavigationLink(destination: Subview(count: $count), isActive: $presentingNextPage) {
EmptyView()
}
}
.onAppear {
self.update()
}
.navigationTitle("a")
.toolbar{
ToolbarItem(placement: .navigationBarTrailing) {
Button("sub") {
presentingNextPage = true /// set to true
}
}
}
}
}
func update() {
things = []
for i in 0...count {
things.append(String(i))
}
}
}
Result:
Put "onAppear{...}" on the NavigationView not the List, like this:
struct ContentView: View {
#State var things: [String] = []
#State var count: Int = 0
var body: some View {
NavigationView{
List {
ForEach(things.indices, id: \.self) { index in
Text(things[index])
}
}
.navigationTitle("a")
.toolbar{
NavigationLink(destination: Subview(count: $count), label: {
Text("sub")
})
}
}
.onAppear { // <---
update()
}
}

Swift - Update List from different View

I have 2 Views in my Swift Project and when I click on the Button on the secondView, I want to update the List in the First View. I don't know how to do it! If I use a static variable in my MainView and then edit this variable from the secondView, it works, but it won't update. And if I don't use static and instead use #State, it would update, but I can't access it from my secondView.
Here is the Code below:
import SwiftUI
struct ContentView: View {
var body: some View {
TabView {
MainView()
.tabItem() {
VStack {
Image(systemName: "circle.fill")
Text("MainView")
}
}.tag(0)
UpdateOtherViewFromHere()
.tabItem() {
VStack {
Image(systemName: "circle.fill")
Text("SecondView")
}
}.tag(1)
}
}
}
struct MainView: View {
var arrayList: [CreateListItems] = []
init() {
let a = CreateListItems(name: "First Name!")
let b = CreateListItems(name: "Second Name!")
let c = CreateListItems(name: "Third Name!")
arrayList.append(a)
arrayList.append(b)
arrayList.append(c)
}
var body: some View {
return VStack {
ZStack {
NavigationView {
List {
ForEach(arrayList) { x in
Text("\(x.name)")
}
}.navigationBarTitle("Main View")
}
}
}
}
}
struct UpdateOtherViewFromHere: View {
func updateList() {
//Code that should remove "FirstName" from the List in MainView
}
var body: some View {
return VStack {
Button(action: {
updateList()
}) {
Image(systemName: "heart.slash")
.font(.largeTitle)
Text("Click Me!")
}
}
}
}
struct CreateListItems: Identifiable {
var id: UUID = UUID()
var name: String
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
You can share it using #State and #Binding if you put
struct ContentView: View {
#State var arrayList: [CreateListItems] = []
struct MainView: View {
#Binding var arrayList: [CreateListItems]
struct UpdateOtherViewFromHere: View {
#Binding var arrayList: [CreateListItems]
or you use the MVVM pattern and store the list in an ObservableObject and use #StateObject/#ObservedObject (source) and use #EnvironmentObject(connection) to share it between your Views.
https://developer.apple.com/documentation/swiftui/managing-model-data-in-your-app
class ParentViewModel: ObservableObject{
#Published var arrayList: [CreateListItems] = []
init(){
addSamples()
}
func addSamples() {
let a = CreateListItems(name: "First Name!")
let b = CreateListItems(name: "Second Name!")
let c = CreateListItems(name: "Third Name!")
arrayList.append(a)
arrayList.append(b)
arrayList.append(c)
}
func updateList() {
let a = CreateListItems(name: "\(arrayList.count + 1) Name!")
arrayList.append(a)
}
}
struct ParentView: View {
#StateObject var vm: ParentViewModel = ParentViewModel()
var body: some View {
TabView {
MainView().environmentObject(vm)
.tabItem() {
VStack {
Image(systemName: "circle.fill")
Text("MainView")
}
}.tag(0)
UpdateOtherViewFromHere().environmentObject(vm)
.tabItem() {
VStack {
Image(systemName: "circle.fill")
Text("SecondView")
}
}.tag(1)
}
}
}
struct MainView: View {
#EnvironmentObject var vm: ParentViewModel
var body: some View {
return VStack {
ZStack {
NavigationView {
List {
ForEach(vm.arrayList) { x in
Text(x.name)
}
}.navigationBarTitle("Main View")
}
}
}
}
}
struct UpdateOtherViewFromHere: View {
#EnvironmentObject var vm: ParentViewModel
var body: some View {
return VStack {
Button(action: {
vm.updateList()
}) {
Image(systemName: "heart.slash")
.font(.largeTitle)
Text("Click Me!")
}
}
}
}

Making a combine passthrough publisher less global

Swift 5, iOS 13
I want to use passthroughSubject publisher; but I my gut tells me its a global variable and as such very poor practice. How can make this global variable less global, while still being usable. Here's some code to show what I talking about.
I know there are a dozen other ways to do this, but I wanted to create some simple code to illustrate the issue.
import SwiftUI
import Combine
let switcher = PassthroughSubject<Void,Never>()
struct SwiftUIViewF: View {
#State var nextPage = false
var body: some View {
VStack {
Text("Switcher")
.onReceive(switcher) { (_) in
self.nextPage.toggle()
}
if nextPage {
Page1ViewF()
} else {
Page2ViewF()
}
}
}
}
struct Page1ViewF: View {
var body: some View {
Text("Page 1")
.onTapGesture {
switcher.send()
}
}
}
struct Page2ViewF: View {
var body: some View {
Text("Page 2")
.onTapGesture {
switcher.send()
}
}
}
struct SwiftUIViewF_Previews: PreviewProvider {
static var previews: some View {
SwiftUIViewF()
}
}
Here is possible solution - to hold it in parent and inject into child views:
struct SwiftUIViewF: View {
let switcher = PassthroughSubject<Void,Never>()
#State var nextPage = false
var body: some View {
VStack {
Text("Switcher")
.onReceive(switcher) { (_) in
self.nextPage.toggle()
}
if nextPage {
Page1ViewF(switcher: switcher)
} else {
Page2ViewF(switcher: switcher)
}
}
}
}
struct Page1ViewF: View {
let switcher: PassthroughSubject<Void,Never>
var body: some View {
Text("Page 1")
.onTapGesture {
self.switcher.send()
}
}
}
struct Page2ViewF: View {
let switcher: PassthroughSubject<Void,Never>
var body: some View {
Text("Page 2")
.onTapGesture {
self.switcher.send()
}
}
}
An example using #EnvironmentObject.
Let SDK take care of observing / passing things for you, rather than setting up yourself.
Especially when your usage is a simple toggle.
import SwiftUI
import Combine
final class EnvState: ObservableObject { #Published var nextPage = false }
struct SwiftUIViewF: View {
#EnvironmentObject var env: EnvState
var body: some View {
VStack {
Text("Switcher")
if env.nextPage {
Page1ViewF()
} else {
Page2ViewF()
}
}
}
}
struct Page1ViewF: View {
#EnvironmentObject var env: EnvState
var body: some View {
Text("Page 1")
.onTapGesture {
env.nextPage.toggle()
}
}
}
struct Page2ViewF: View {
#EnvironmentObject var env: EnvState
var body: some View {
Text("Page 2")
.onTapGesture {
env.nextPage.toggle()
}
}
}
struct SwiftUIViewF_Previews: PreviewProvider {
static var previews: some View {
SwiftUIViewF().environmentObject(EnvState())
}
}

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