How to Call a Function When a Swiftui Picker Selection Changes

Is there a way to call a function when a SwiftUI Picker selection changes?

If the @State value will be used in a View, you don't need extra variable name

  struct BuilderPicker: View {
// let name: String = ""
 let options: Array<String> = ["1", "2","3","4","5"]
 @State var selectedOption = 0
 var body: some View {
    HStack {
        Text(options[selectedOption])
            .font(.body)
            .padding(.leading, 10)
        Picker(selection: $selectedOption, label:    Text(options[selectedOption])) {
            ForEach(0 ..< options.count) {
                Text(self.options[$0]).tag($0)
            }
        }.pickerStyle(SegmentedPickerStyle())
            .padding(.trailing, 25)}
//        }.onTapGesture {
//            self.selectedOption = self.selectedOption == 0 ? 1 : 0
//        }
        .padding(.init(top: 10, leading: 10, bottom: 10, trailing: 0))
        .border(Color.secondary, width: 3)
        .padding(.init(top: 0, leading: 15, bottom: 0, trailing: 15))
        .font(.body)
    }


 }

If you need separated operation on the @State, the simplest way is adding one line : onReceive() to the view.

  HStack {
        Text("")
            .font(.body)
            .padding(.leading, 10)
        Picker(selection: $selectedOption, label: Text("")) {
            ForEach(0 ..< options.count) {
                Text(self.options[$0]).tag($0)
            }
        }.pickerStyle(SegmentedPickerStyle())
            .padding(.trailing, 25)}
  //        }.onTapGesture {
 //            self.selectedOption = self.selectedOption == 0 ? 1 : 0
 //        }
        .padding(.init(top: 10, leading: 10, bottom: 10, trailing: 0))
        .border(Color.secondary, width: 3)
        .padding(.init(top: 0, leading: 15, bottom: 0, trailing: 15))
        .font(.body)
        .onReceive([self.selectedOption].publisher.first()) { (value) in
            print(value)
    }

Is there a way to call a function when a SwiftUI Picker selection changes an EnvironmentObject?

There is much simpler approach, which looks more appropriate for me.

The generic schema as follows

Picker("Label", selection: Binding(    // proxy binding
    get: { self.viewModel.value },     // get value from storage
    set: {
            self.viewModel.value = $0  // set value to storage

            self.anySideEffectFunction() // didSet function
    }) {
       // picker content
    }

How to call on a view when a Picker selection is selected

Here is an example for solving your problem:

enum CameraEnum: String, CaseIterable { case telephoto, wide, ultraWide}

struct ContentView: View {
    
    @State private var selection: CameraEnum = .wide
    
    var body: some View {
        
        Picker(selection: $selection, label: EmptyView(), content: {

            ForEach(CameraEnum.allCases, id:\.self) { item in
                
                Text(item.rawValue)
                
            }
 
        })
        .onAppear() { cameraFunction(selection) }
        .onChange(of: selection, perform: { value in cameraFunction(value) })
        
    }
    
    private func cameraFunction(_ cameraValue: CameraEnum) {
        print("Your camera selection is:", cameraValue)
    }
    
}

SwiftUI Picker OnChange not being called when new option is being selected

For seasonSelection to work in a Picker, add a .tag() to Text(...) and make sure it is of the same type as the seasonSelection, for example (assuming index is of type Int):

NOTE: this works for macCatalyst, for macOS only, see EDIT.

Picker(selection: $seasonSelection, label: Text("Selected Season")){
  ForEach(userData.userData.lastUsedSeason, id:\.self) { index in
    Text(seasonData.seasons[index].seasonName()).tag(index)  // <-- here
  }
}
 .onChange(of: seasonSelection, perform:  { _ in
  seasonData.seasons[0].testPrint()
 })

EDIT: sample code that shows how to use tag with seasonSelection in .onReceive() on macOS only, and .onChange() for macCatalyst.

import SwiftUI
import Combine

@main
struct TestMacApp: App {
    var body: some Scene {
        WindowGroup {
            Text("demo").frame(width: 480.0, height: 320.0)
        }
        .commands {
            SandStatCommands()
        }
    }
}

struct SandStatCommands: Commands {
    @State var seasons = ["Spring","summer","autumn","winter"]  // array of values
    @State var seasonSelection: Int = 0  // <-- here initial selection
    
    var body: some Commands {
        CommandMenu("Season"){
            Button("Add Season"){
                seasons.append(String(UUID().uuidString.prefix(6))) // for demo, add a random name
            }
            Picker(selection: $seasonSelection, label: Text("Selected Season")){
                ForEach(0..<seasons.count, id:\.self) { index in
                    Text(seasons[index]).tag(index)  // <-- here tag
                }
            }
           // .onChange(of: seasonSelection) { value in
           //     print("---> seasonSelection value: \(value)")
           //  }
          .onReceive(Just(seasonSelection)) { value in
             print("---> seasonSelection value: \(value)")
          }
        }
    }
}

SwiftUI Picker onChange or equivalent?

Deployment target of iOS 14 or newer

Apple has provided a built in onChange extension to View, which can be used like this:

struct MyPicker: View {
    @State private var favoriteColor = 0

    var body: some View {
        Picker(selection: $favoriteColor, label: Text("Color")) {
            Text("Red").tag(0)
            Text("Green").tag(1)
        }
        .onChange(of: favoriteColor) { tag in print("Color tag: \(tag)") }
    }
}

---

Deployment target of iOS 13 or older

struct MyPicker: View {
    @State private var favoriteColor = 0

    var body: some View {
        Picker(selection: $favoriteColor.onChange(colorChange), label: Text("Color")) {
            Text("Red").tag(0)
            Text("Green").tag(1)
        }
    }

    func colorChange(_ tag: Int) {
        print("Color tag: \(tag)")
    }
}

Using this helper

extension Binding {
    func onChange(_ handler: @escaping (Value) -> Void) -> Binding<Value> {
        return Binding(
            get: { self.wrappedValue },
            set: { selection in
                self.wrappedValue = selection
                handler(selection)
        })
    }
}

How do I add action on picker on selection of item in swiftUI?

I found 3 different ways to achieve this. The last one I took here. So, there are all these ways, you can choose which you want:

struct PickerOnChange: View {

    private var options = ["add", "edit", "delete"]
    @State private var selectedOption = 0
    @State private var choosed = 0

    var body: some View {

        VStack {

            Picker(selection: $selectedOption.onChange(changeViewWithThirdWay), label: Text("Choose action")) {
                ForEach(0 ..< self.options.count) {
                    Text(self.options[$0]).tag($0)
                }
            }.pickerStyle(SegmentedPickerStyle())

            // MARK: first way
            VStack {
                if selectedOption == 0 {
                    Text("add (first way)")
                } else if selectedOption == 1 {
                    Text("edit (first way)")
                } else {
                    Text("delete (first way)")
                }

                Divider()

                // MARK: second way
                ZStack {

                    AddView()
                        .opacity(selectedOption == 0 ? 1 : 0)

                    EditView()
                        .opacity(selectedOption == 1 ? 1 : 0)

                    DeleteView()
                        .opacity(selectedOption == 2 ? 1 : 0)
                }

                Divider()

                // MARK: showing third way
                Text("just to show, how to use third way: \(self.choosed)")

                Spacer()

            }

        }

    }

    func changeViewWithThirdWay(_ newValue: Int) {
        print("will change something in third way with: \(choosed), you can do everything in this function")
        withAnimation {
            choosed = newValue
        }

    }

}

// MARK: the third way
extension Binding {
    func onChange(_ handler: @escaping (Value) -> Void) -> Binding<Value> {
        return Binding(
            get: { self.wrappedValue },
            set: { selection in
                self.wrappedValue = selection
                handler(selection)
        })
    }
}

You'll achieve this with code snippet:

Is there a way to call a function when a slider is used in swift?

We can use computable in-inline binding with side-effect for this (and you can remove onChange at all), here is a demo

 Slider(value: Binding(get: { noteLength }, 
     set: { 
        // willSet side-effect here       // << here !!
        noteLenght = $0
        // didSet side-effect here       // << here !!
     }), 
    in: 0.1...3.01, step: 0.1)
    .onChange(of: noteLength, perform:  { value in
        defaults.set(value, forKey: "noteLengthEx1")
        levelIndex = 4
    })

SwiftUI Picker not changing selection value

Here is an approach for you:

struct ContentView: View {
    
    @State private var selection: PickerType = PickerType.none
    
    var body: some View {
        
        OrderPicker(selection: $selection)
    }
}

struct OrderPicker: View {
    
    @Binding var selection: PickerType
    
    var body: some View {
        Form {
            Picker("Order in list", selection: $selection) {
                ForEach(PickerType.allCases, id: \.self) { item in
                    Text(item.rawValue)
                    
                }
            }
            .pickerStyle(WheelPickerStyle())
            .onChange(of: selection, perform: { newValue in
                print(newValue.rawValue, newValue.intValue)
            })
        }
        
    }

}

enum PickerType: String, CaseIterable {
    
    case none, first, second, third
    
    var intValue: Int {
        switch self {
        case .none: return 0
        case .first: return 1
        case .second: return 2
        case .third: return 3
        }
    }
    
}

---

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