SwiftUI Picker not trigger `onChange` first time when inside Menu in MacOS

I displayed the value on Picker title, it turns out that first time select another option , the value did changed, but the onChange is not trigger

Picker("value \(value)", selection: $value) {
     //...
}

if I move onChange to Menu, the problem disappeared

Menu("menu") {
        Picker("value \(value)", selection: $value) {
          Text("A").tag("a")
          Text("B").tag("b")
          Text("C").tag("c")
        }
        .pickerStyle(.inline)
      }
      .onChange(of: value) { oldValue, newValue in
        print("onChange", newValue)
      }

but my goal is to encapsulate Picker into a controlled component similar to React, so I have to put state inside menu

import SwiftUI

struct TBSelect: View {
  let title: String;
  let value: String;
  let options: Array<TBSelectOption>;
  let tip: String;
  let onChange: (_ value: String) -> Void;
  
  @State private var innerValue: String;
  
  struct TBSelectOption {
    let title: String;
    let value: String;
    let systemImage: String?;
  }
  
  init(title: String, value: String, options: Array<TBSelectOption>, tip: String = "", onChange: @escaping (_ value: String) -> Void) {
    _innerValue = State(initialValue: value);
    
    self.title = title
    self.value = value
    self.options = options
    self.tip = tip
    self.onChange = onChange;
  }
  
  var body: some View {
    Picker(title, selection: $innerValue) {
      ForEach(options, id: \.value) { option in
        if let systemImage = option.systemImage {
          Label(option.title, systemImage: systemImage)
            .tag(option.value)
        } else {
          Text(option.title)
            .tag(option.value)
        }
      }
    }
    .help(tip)
    .onChange(of: innerValue) { oldValue, newValue in
      onChange(newValue)
    }
  }
}

There is effectively something weird here. At first change, Picker does not react.

That seems to be an old bug (or undocumented behaviour): https://forums.developer.apple.com/forums/thread/688685

In addition of the solution you found, I implemented the Spacer().onChange trick and it works:

struct swiftuiTestApp: App {
    @State private var value = "a"

    var body: some Scene {
        WindowGroup {
            Menu("menu \(value)") {
                Picker("", selection: $value) {
                    Text("A").tag("a")
                    Text("B").tag("b")
                    Text("C").tag("c")
                }
                .pickerStyle(.inline)
                .onChange(of: value) { oldValue, newValue in
                    print("onChange", oldValue, newValue)
                }
            }
            Spacer().onChange(of: value) { oldValue, newValue in
                print("Spacer onChange", oldValue, newValue)
            }
        }
    }
}

Here is the log:

Spacer onChange a b      // First change does not trigger picker onChange, but triggers Spacer()
Spacer onChange b c      // next change does trigger picker onChange, and Spacer()
onChange b c

You should file a bug report.

I think there is something wrong with Menu in MacOS, toogle insdie Menu has the same problem

struct swiftuiTestApp: App {
  @State private var val = false;
  
  var body: some Scene {
    WindowGroup {
      Menu("menu") {
        Toggle(isOn: $val) {
          Text("open")
        }.onChange(of: val) { oldValue, newValue in
          print("onChange", newValue)
        }
      }
    }
  }
}

@chijun89 I tested this out and it looks like a bug on macOS! Can you please file a bug report at https://feedbackassistant.apple.com and add the code snippet. Please paste the FB number here.

Thanks

A week has passed and I haven't received any feedback from Apple.

https://feedbackassistant.apple.com/feedback/15061288