Swiftui Textfield Resets Value and Ignores Binding

SwiftUI TextField resets value and ignores binding

Here you go!

class ViewModel: ObservableObject {
    @Published var s = "Default String"
}

struct ContentView: View {
    @StateObject private var vm = ViewModel()
    var body: some View {
        TextField("S:", text: $vm.s)
            .padding()
    }
}

For use in multiple views, in every view where you'd like to use the model add:

@EnvironmentObject private var vm: ViewModel 

But don't forget to inject the model to the main view:

ContentView().environmentObject(ViewModel())

SwiftUI textfield proxy binding code to ignore spaces not working?

No, we should not return, there should be assignment, because it generates feedback.

It can be like

     TextField(placeholder, text: Binding(
        get: { self.input },
        set: {
            var newValue = $0
            newValue.removeAll { $0 == " " }  // << here !!
            self.input = newValue
    }))

Capture Textfield value without hitting return key in SwiftUI

Firstly, add @State variable 'year':

@State private var year: Int = 0

Secondly, pass Binding to TextField 'text' parameter and use formatter inside, like this:

        TextField("Year", text: Binding<String>(
                get: { String(year) },
                set: {
                    if let value = NumberFormatter().number(from: $0) {
                        self.year = value.intValue
                        print("Year: \(year)")
                    }
                }
        ))

It will print 'year' value until something else but number will be pressed on the keyboard.
To leave only number input you can set keyboardType to your TextField:

.keyboardType(UIKeyboardType.numberPad)

Recognize changes in SwiftUI TextField with double value

On iOS 15 you can use TextField ("Hello", value: $someDoubleValue, formatter: <your NumberFormatter here>) and the value propagates fine.

On iOS 14, it doesn't seem to work binding a TextField to a Double value with a formatter.

So the following works fine in iOS 15, but does not work in iOS 14.

Note The double value is nested here because this is a code snippet taken from what I'm working on right now.

public class MyViewModel: ObservableObject {
    @Published var child: ChildObject
}

public class ChildObject: Identifiable, ObservableObject {
    @Published var doubleValue: Double
}

public struct FancyPantsView: View {
     @ObservedObject var viewModel: MyViewModel

     public var body: some View {
          VStack {
               TextField ("Hello", value: $viewModel.child.doubleValue, formatter: amountFormatter)
                    .keyboardType(.decimalPad)
          }
     }

     let amountFormatter: NumberFormatter = {
          let formatter = NumberFormatter()
          formatter.zeroSymbol = ""
          return formatter
     }()
}

SwiftUI TextField not updating in sibling View (with video)

Use @Binding instead of @State

It is important to remember that TextField is actually a SwiftUI View (via inheritance). The parent child relationship is actually TaskRow -> TextField.

@State is used for representing the 'state' of a view. While this value can be passed around, it's not meant to be written to by other views (it has a single source of truth).

In the case above, I am actually passing title (via $ prefix) to another view while expecting either the parent or child to modify the title property. @Binding supports 2 way communication between views or a property and view.

@State Apple Docs: https://developer.apple.com/documentation/swiftui/state

@Binding Apple Docs: https://developer.apple.com/documentation/swiftui/binding

Jared Sinclair's Wrapper Rules: https://jaredsinclair.com/2020/05/07/swiftui-cheat-sheet.html

Changing the TaskRow and TaskDetail views fixed the behavior:

TaskRow.swift

import SwiftUI
import CoreData

struct TaskRow: View {

    @Environment(\.managedObjectContext) var context
    @ObservedObject var task: Task
    
    @Binding private var title: String
    
    init(task: Task) {
        self.task = task
        self._title = Binding(get: {
            return task.title ?? ""
        }, set: {
            task.title = $0
        })
        print("INIT - TaskRow Initialized: title=\(task.title ?? ""), completed=\(task.completed)")
    }
    
    var body: some View {
        HStack {
            TextField("Task Name", text: self.$title) {
                self.save()
            }.foregroundColor(.black)
            Spacer()
            Text("\(self.task.position)")
            Button(action: {
                self.task.completed.toggle()
                self.save()
            }, label: {
                Image(systemName: self.task.completed ? "checkmark.square" : "square")
            }).buttonStyle(BorderlessButtonStyle())
        }
    }
}

extension TaskRow {
    func save() {
        try? self.context.save()
        print("SAVE - TaskRow")
    }
}

TaskDetail.swift

import SwiftUI

struct TaskDetail: View {
    
    @Environment(\.managedObjectContext) var context
    @ObservedObject var task: Task
    
    @Binding private var title: String
    
    init(task: Task) {
        self.task = task
        self._title = Binding(get: {
            return task.title ?? ""
        }, set: {
            task.title = $0
        })
        print("INIT - TaskDetail Initialized: title=\(task.title ?? ""), completed=\(task.completed)")
    }
    
    var body: some View {
        Form {
            Section {
                TextField("Task Name", text: self.$title) {
                    self.save()
                }.foregroundColor(.black)
            }
            Section {
                Button(action: {
                    self.task.completed.toggle()
                    self.save()
                }, label: {
                    Image(systemName: self.task.completed ? "checkmark.square" : "square")
                }).buttonStyle(BorderlessButtonStyle())
            }
        }
    }
}

extension TaskDetail {
    func save() {
        try? self.context.save()
        print("SAVE - TaskDetail")
    }
}

SwiftUI @Binding update doesn't refresh view

You have not misunderstood anything. A View using a @Binding will update when the underlying @State change, but the @State must be defined within the view hierarchy. (Else you could bind to a publisher)

Below, I have changed the name of your ContentView to OriginalContentView and then I have defined the @State in the new ContentView that contains your original content view.

import SwiftUI

struct OriginalContentView: View {
    @Binding var isSelected: Bool

    var body: some View {
        Button(action: {
            self.isSelected.toggle()
        }) {
            Text(isSelected ? "Selected" : "Not Selected")
        }
    }
}

struct ContentView: View {
    @State private var selected = false

    var body: some View {
       OriginalContentView(isSelected: $selected)
    }
}

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

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