I have simple viewModel:
final class EmployeeListViewModel: ObservableObject {
#Published var list = [Employee]()
init() {
// some request
self.list = [Employee, Employee]
}
}
And have a view:
struct EmployeeView: View {
#ObservedObject var viewModel = EmployeeListViewModel()
#State private var showContents: [Bool] = Array(repeating: false, count: viewModel.list.count)// <- error throws here
var body: some View {
GeometryReader { fullView in
ScrollView {
VStack(spacing: 40) {
ForEach(self.viewModel.list) { employee in
Text(employee.firstName).foregroundColor(.black)
}
}
}
}
}
}
Error text:
Cannot use instance member 'viewModel' within property initializer; property initializers run before 'self' is available
I tried change it with init:
struct EmployeeView: View {
#ObservedObject var viewModel = EmployeeListViewModel()
#State private var showContents: [Bool]
init() {
_showContents = State(initialValue: Array(repeating: false, count: viewModel.list.count)) // <- error
}
var body: some View {
GeometryReader { fullView in
ScrollView {
VStack(spacing: 40) {
ForEach(self.viewModel.list) { employee in
Text(employee.firstName).foregroundColor(.black)
}
}
}
}
}
}
But it also throws error:
'self' used before all stored properties are initialized
this throws on I call viewModel on init()
How to solve it? #State i use for card view. There I simplified views for easy understand.
First initialise the state variable to an empty array
#State private var showContents: [Bool] = []
then set it in the init
init() {
showContents = Array(repeating: false, count: viewModel.list.count)
}
You shouldn't initialise the view model property in the view but rather use dependency injection
init(viewModel: EmployeeListViewModel) {
self.viewModel = viewModel
showContents = Array(repeating: false, count: viewModel.list.count)
}
Here is possible solution
struct EmployeeView: View {
#ObservedObject var viewModel: EmployeeListViewModel // << declare
#State private var showContents: [Bool] // << declare
init() {
let vm = EmployeeListViewModel() // create here !!
// initialize both below
self.viewModel = vm
self._showContents = State(initialValue: Array(repeating: false,
count: vm.list.count))
}
Related
Is there any way to bind a data model in swiftui?
I have coded like below and need to build a struct so that I can use it in multiple views but the problem is to know how to bind a #publish data model in swiftui?
var birds: [PlayerItem] = [PlayerItem(id: UUID(), playershow: false)]
var dogs: [PlayerItem] = [PlayerItem(id: UUID(), playershow: true)]
class Controller: ObservableObject {
#Published var bird = birds
#Published var dog = dogs
}
struct PlayerItem: Hashable {
var id = UUID()
var playerShow: Bool
}
struct ContentView: View {
#EnvironmentObject var control: Controller
var body: some View {
setButton(isOn: $Controller.bird)
}
}
struct setButton: View {
#Binding var isOn: [PlayerItem]
var body: some View {
Button(action: {
self.isOn[0].toggle()
}) {
Text(isOn[0] ? "Off" : "On")
}
}
}
I wrote the following code:
#Binding var isOn: [PlayerItem]
However, it complained the following:
Value of type 'EnvironmentObject<controller>.Wrapper' has no dynamic member 'isOn' using the key path from the root type 'Controller'
try the following code, it shows how to use #Binding and how you have to use playershow
class Controller: ObservableObject {
#Published var bird = [Playeritem(id: UUID(), playershow: false)]
#Published var dog = [Playeritem(id: UUID(), playershow: true)]
}
struct Playeritem: Hashable {
var id = UUID()
var playershow: Bool
}
struct ContentView: View {
#StateObject var control = Controller() // <-- for testing
var body: some View {
setButton(isOn: $control.bird) // <-- here control
}
}
struct setButton: View {
#Binding var isOn: [Playeritem]
var body: some View {
Button(action: {
self.isOn[0].playershow.toggle() // <-- here playershow
}) {
Text(isOn[0].playershow ? "Off" : "On") // <-- here playershow
}
}
}
I want to decouple my ViewModel and View layer to increase testability of my Views.
Therefore, I want to keep my property states inside view and only init them as I needed.
But I cannot initialize my #Binding or #States with #Published properties. Is there a way to couple them inside init function?
I just add example code below to
instead of
import SwiftUI
class ViewModel: ObservableObject {
#Published var str: String = "a"
#Published var int: Int = 1 { didSet { print("ViewModel int = \(int)")} }
init() {
print("ViewModel initialized")
}
}
struct ContentView: View {
#ObservedObject vM = ViewModel()
var body: some View {
Button(action: { vM.int += 1; print(int) }, label: {
Text("Button")
})
}
}
I want to achieve this without using #ObservedObject inside my view.
import SwiftUI
class ViewModel: ObservableObject {
#Published var str: String = "a"
#Published var int: Int = 1 { didSet { print("ViewModel int = \(int)")} }
init() {
print("ViewModel initialized")
}
}
struct ContentView: View {
#Binding var str: String
#Binding var int: Int
var body: some View {
Button(action: { int += 1; print(int) }, label: {
Text("Button")
})
}
}
extension ContentView {
init(viewModel:ObservedObject<ViewModel> = ObservedObject(wrappedValue: ViewModel())) {
// str: Binding<String> and viewModel.str: Published<String>.publisher
// type so that I cannot bind my bindings to viewModel. I must accomplish
// this by using #ObservedObject but this time my view couples with ViewModel
_str = viewModel.wrappedValue.$str
_int = viewModel.wrappedValue.$int
print("ViewCreated")
}
}
// Testing Init
ContentView(str: Binding<String>, int: Binding<Int>)
// ViewModel Init
ContentView(viewModel: ViewModel)
This way I can't bind them each other, I just want to bind my binding or state properties to published properties.
I have realized that by Binding(get:{}, set{}), I can accomplish that. if anyone want to separate their ViewModel and View layer, they can use this approach:
import SwiftUI
class ViewModel: ObservableObject {
#Published var str: String = "a"
#Published var int: Int = 1 { didSet { print("ViewModel int = \(int)")} }
init() {
print("ViewModel initialized")
}
}
struct ContentView: View {
#Binding var str: String
#Binding var int: Int
var body: some View {
Button(action: { int += 1; print(int) }, label: {
Text("Button")
})
}
}
extension ContentView {
init(viewModel:ViewModel = ViewModel()) {
_str = Binding ( get: { viewModel.str }, set: { viewModel.str = $0 } )
_int = Binding ( get: { viewModel.int }, set: { viewModel.int = $0 } )
print("ViewCreated")
}
}
I have two views, embedded in TabView.
I am using userdefaults in a class called usersettings.
class UserSettings: ObservableObject {
#Published var favList: [String] {
willSet {
print("willset")
}
didSet {
UserDefaults.standard.set(favList, forKey: "isAccountPrivate")
print("didset")
}
}
init() {
self.favList = UserDefaults.standard.object(forKey: "isAccountPrivate") as? [String] ?? ["Sepetiniz Boş"]
}
}
In Button View, which acts like add/remove favorite. It successfully adds and remove from the UserDefaults. But when I add something it does not show on the other view (please see the next code after FavButton)
struct FavButton: View {
#Binding var passedFood: String
#ObservedObject var userSettings = UserSettings()
var body: some View {
Button(action: {
if userSettings.favList.contains(passedFood) {
userSettings.favList.remove(at: userSettings.favList.firstIndex(of: passedFood )!)
} else {
userSettings.favList.append(passedFood)
}
})
}
}
But it does not update my list in this other view unless I close and open my app. If I remove something from the list, it actually removes from the userdefault.
If I add a new word within this view, it works too.
My only problem is when I add something from another view (FavButton) it does not show in this view (FavView).
struct FavView: View {
#ObservedObject var userSettings = UserSettings()
#State private var newWord = ""
var body: some View {
NavigationView {
List {
TextField("Ürün Ekleyin...", text: $newWord, onCommit: addNewWord)
ForEach( self.userSettings.favList, id: \.self) { list in
Text(list)
.font(.headline)
.padding()
}
.onDelete(perform: self.deleteRow)
}
.navigationTitle("Sepetim")
}
}
private func deleteRow(at indexSet: IndexSet) {
self.userSettings.favList.remove(atOffsets: indexSet)
}
private func addNewWord() {
let answer = newWord.lowercased().trimmingCharacters(in: .whitespacesAndNewlines)
self.userSettings.favList.append(answer)
guard answer.count > 0 else {
return
}
newWord = ""
}
}
A better approach to follow the SwiftUI idiom is to use the .environmentObject() modifier.
When you declare your app:
struct AppScene: App {
#StateObject private var userSettings = UserSettings() // Use state object to persist the object
var body: some Scene {
WindowGroup {
ContentView()
.environmentObject(userSettings) // Inject userSettings into the environment
}
}
}
and then in you ContentView you can reach into your environment and get the object:
struct ContentView: View {
#EnvironmentObject private var userSettings: UserSettings
var body: some View {
Text("Number of items in favList: \(userSettings.favList.count)")
}
}
You need to use same instance of UserSettings in all views where you want to have observed user settings, like
class UserSettings: ObservableObject {
static let global = UserSettings()
//... other code
}
and now
struct FavButton: View {
#ObservedObject var userSettings = UserSettings.global // << here !!
// ... other code
}
and
struct FavView: View {
#ObservedObject var userSettings = UserSettings.global // << here !!
// ... other code
}
I have a view with a ForEach with multiple instances of another view. I want to be able to:
Click a button in the main view and trigger validation on the nested views, and
On the way back, populate an array with the results of the validations
I've simplified the project so it can be reproduced. Here's what I have:
import SwiftUI
final class AddEditItemViewModel: ObservableObject {
#Published var item : String
#Published var isValid : Bool
#Published var doValidate: Bool {
didSet{
print(doValidate) // This is never called
validate()
}
}
init(item : String, isValid : Bool, validate: Bool) {
self.item = item
self.isValid = isValid
self.doValidate = validate
}
func validate() { // This is never called
isValid = Int(item) != nil
}
}
struct AddEditItemView: View {
#ObservedObject var viewModel : AddEditItemViewModel
var body: some View {
Text(viewModel.item)
}
}
final class AddEditProjectViewModel: ObservableObject {
let array = ["1", "2", "3", "nope"]
#Published var countersValidationResults = [Bool]()
#Published var performValidation = false
init() {
for _ in array {
countersValidationResults.append(false)
}
}
}
struct ContentView: View {
#ObservedObject var viewModel : AddEditProjectViewModel
#State var result : Bool = false
var body: some View {
VStack {
ForEach(
viewModel.countersValidationResults.indices, id: \.self) { i in
AddEditItemView(viewModel: AddEditItemViewModel(
item: viewModel.array[i],
isValid: viewModel.countersValidationResults[i],
validate: viewModel.performValidation
)
)
}
Button(action: {
viewModel.performValidation = true
result = viewModel.countersValidationResults.filter{ $0 == false }.count == 0
}) {
Text("Validate")
}
Text("All is valid: \(result.description)")
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView(viewModel: AddEditProjectViewModel())
}
}
When I change the property in the main view, the property doesn't change in the nested views, even though it's a #Published property.
Since this first step is not working, I haven't even been able to test the second part (updating the array of books with the validation results)
I need the setup to be like this because if an item is not valid, that view will show an error message, so the embedded views need to know whether they are valid or not.
UPDATE:
My issue was that you can't seem to be able to store Binding objects in view models, only in views, so I moved my properties to the view, and it works:
import SwiftUI
final class AddEditItemViewModel: ObservableObject {
#Published var item : String
init(item : String) {
self.item = item
print("item",item)
}
func validate() -> Bool{
return Int(item) != nil
}
}
struct AddEditItemView: View {
#ObservedObject var viewModel : AddEditItemViewModel
#Binding var doValidate: Bool
#Binding var isValid : Bool
init(viewModel: AddEditItemViewModel, doValidate:Binding<Bool>, isValid : Binding<Bool>) {
self.viewModel = viewModel
self._doValidate = doValidate
self._isValid = isValid
}
var body: some View {
Text("\(viewModel.item): \(isValid.description)").onChange(of: doValidate) { _ in isValid = viewModel.validate() }
}
}
struct ContentView: View {
#State var performValidation = false
#State var countersValidationResults = [false,false,false,false] // had to hard code this here
#State var result : Bool = false
let array = ["1", "2", "3", "nope"]
// init() {
// for _ in array {
// countersValidationResults.append(false) // For some weird reason this appending doesn't happen!
// }
// }
var body: some View {
VStack {
ForEach(array.indices, id: \.self) { i in
AddEditItemView(viewModel: AddEditItemViewModel(item: array[i]), doValidate: $performValidation, isValid: $countersValidationResults[i])
}
Button(action: {
performValidation.toggle()
result = countersValidationResults.filter{ $0 == false }.count == 0
}) {
Text("Validate")
}
Text("All is valid: \(result.description)")
Text(countersValidationResults.description)
}
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}
I'm having trouble reconciling the question with the example code and figuring out what's supposed to be happening. Think that there are a few issues going on.
didSet will not get called on #Published properties. You can (SwiftUI - is it possible to get didSet to fire when changing a #Published struct?) but the gist is that it's not a normal property, because of the #propertyWrapper around it
You say in your question that you want a "binding", but you never in fact us a Binding. If you did want to bind the properties together, you should look into using either #Binding or creating a binding without the property wrapper. Here's some additional reading on that: https://swiftwithmajid.com/2020/04/08/binding-in-swiftui/
You have some circular logic in your example code. Like I said, it's a little hard to figure out what's a symptom of the code and what you're really trying to achieve. Here's an example that strips away a lot of the extraneous stuff going on and functions:
struct AddEditItemView: View {
var item : String
var isValid : Bool
var body: some View {
Text(item)
}
}
final class AddEditProjectViewModel: ObservableObject {
let array = ["1", "2", "3"]// "nope"]
#Published var countersValidationResults = [Bool]()
init() {
for _ in array {
countersValidationResults.append(false)
}
}
func validate(index: Int) { // This is never called
countersValidationResults[index] = Int(array[index]) != nil
}
}
struct ContentView: View {
#ObservedObject var viewModel : AddEditProjectViewModel
#State var result : Bool = false
var body: some View {
VStack {
ForEach(
viewModel.countersValidationResults.indices, id: \.self) { i in
AddEditItemView(item: viewModel.array[i], isValid: viewModel.countersValidationResults[i])
}
Button(action: {
viewModel.array.enumerated().forEach { (index,_) in
viewModel.validate(index: index)
}
result = viewModel.countersValidationResults.filter{ $0 == false }.count == 0
}) {
Text("Validate")
}
Text("All is valid: \(result.description)")
}
}
}
Note that it your array, if you include the "nope" item, not everything validates, since there's a non-number, and if you omit it, everything validates.
In your case, there really wasn't the need for that second view model on the detail view. And, if you did have it, at least the way you had things written, it would have gotten you into a recursive loop, as it would've validated, then refreshed the #Published property on the parent view, which would've triggered the list to be refreshed, etc.
If you did get in a situation where you needed to communicate between two view models, you can do that by passing a Binding to the parent's #Published property by using the $ operator:
class ViewModel : ObservableObject {
#Published var isValid = false
}
struct ContentView : View {
#ObservedObject var viewModel : ViewModel
var body: some View {
VStack {
ChildView(viewModel: ChildViewModel(isValid: $viewModel.isValid))
}
}
}
class ChildViewModel : ObservableObject {
var isValid : Binding<Bool>
init(isValid: Binding<Bool>) {
self.isValid = isValid
}
func toggle() {
isValid.wrappedValue.toggle()
}
}
struct ChildView : View {
#ObservedObject var viewModel : ChildViewModel
var body: some View {
VStack {
Text("Valid: \(viewModel.isValid.wrappedValue ? "true" : "false")")
Button(action: {
viewModel.toggle()
}) {
Text("Toggle")
}
}
}
}
I have a class which I want to initialize with a Binding var that is set in another View.
View ->
struct CoverPageView: View {
#State var numberOfNumbers:Int
var body: some View {
NavigationView {
GeometryReader { geometry in
VStack(alignment: .center, spacing: 0){
TextField("Multiplication Upto:", value: self.$numberOfNumbers, formatter: NumberFormatter())
}
}
}
}
CLASS WHICH NEEDS TO BE INITIALIZED USING THE #Binding var $numberofNumbers -
import SwiftUI
class MultiplicationPractice:ObservableObject {
#Binding var numberOfNumbers:Int
var classNumofNumbers:Int
init() {
self.classNumofNumbers = self.$numberOfNumbers
}
}
The init statement obviously gives the error that self is not initialized and the instance var is being used to initialize which is not allowed.
How do I circumvent this? The class needs to be initialized with the number the user enters on the first view. I have written approx. code here so ignore any typos please.
Typically you'd initialize MultiplicationPractice in CoverPageView with a starting value:
#ObservedObject var someVar = MultiplicationPractice(NoN:123)
And of course, add a supporting init statement:
class MultiplicationPractice:ObservableObject {
init(NoN: Int) {
self.numberOfNumbers = val
}
and you wouldn't want to wrap your var with #Binding, instead wrap it with #Published:
class MultiplicationPractice:ObservableObject {
#Published var numberOfNumbers:Int
...
In your particular case I would even drop the numberOfNumbers var in your CoverPageView, and instead use the direct variable of the above someVar:
struct CoverPageView: View {
//removed #State var numberOfNumbers:Int
#ObservedObject var someVar = MultiplicationPractice(123)
...
TextField("Multiplication Upto:", value: self.$someVar.numberOfNumbers, formatter: NumberFormatter())
You'll notice that I passed in the sub-var of the #ObservedObject as a binding. We can do this with ObservableObjects.
Edit
I see now what you're trying to do, you want to pass a binding along across your ViewModel, and establish an indirect connection between your view and model. While this may not be the way I'd personally do it, I can still provide a working example.
Here is a simple example using your struct names:
struct MultiplicationGame {
#Binding var maxNumber:String
init(maxNumber: Binding<String>) {
self._maxNumber = maxNumber
print(self.maxNumber)
}
}
class MultiplicationPractice:ObservableObject {
var numberOfNumbers: Binding<String>
#Published var MulGame:MultiplicationGame
init(numberOfNumbers: Binding<String> ) {
self.numberOfNumbers = numberOfNumbers
self.MulGame = MultiplicationGame(maxNumber: numberOfNumbers)
}
}
struct ContentView: View {
#State var someText: String
#ObservedObject var mulPractice: MultiplicationPractice
init() {
let state = State(initialValue: "")
self._someText = state
self.mulPractice = MultiplicationPractice(numberOfNumbers: state.projectedValue)
}
var body: some View {
TextField("put your text here", text: $someText)
}
}
Okay, I don't really understand your question so I'm just going to list a few examples and hopefully one of them will be what you're looking for.
struct SuperView: some View {
#State var value: Int = 0
var body: some View {
SubView(value: self.$value)
}
}
struct SubView: View {
#Binding var value: Int
// This is the same as the compiler-generated memberwise initializer
init(value: Binding<Int>) {
self._value = value
}
var body: some View {
Text("\(value)")
}
}
If I misunderstood and you're just trying to get the current value, do this
struct SuperView: some View {
#State var value: Int = 0
var body: some View {
SubView(value: self.value)
}
}
struct SubView: View {
let value: Int
// This is the same as the compiler-generated memberwise initializer
init(value: Int) {
self.value = value
}
var body: some View {
Text("\(value)")
}
}