选择器选项未动态更新 SwiftUI

Question

I have a picker that needs to dynamically update as it finds new BLE peripherals. However, the picker never updates with the new values.

I had a List that was working fine with the following code, so I know everything is ok in my BLE Manager:

List(bleManager.peripheralsDisp) { peripheral in
    Text(peripheral.displayName)
  }.frame(height: 300)

However, the same code used for the picker, does not work:

Picker(selection: $selectedDevice, label: Text("")) {
    ForEach(self.bleManager.peripheralsDisp, id: \.self) { peripheral in
      Text(peripheral.displayName)
    }
  }
  .frame(width: 200, height: 40, alignment: .center)

Any advice as to how to get the picker options to dynamically update would be much appreciated

EDIT:

Here is my BLEManager.swift file

import Foundation
import CoreBluetooth

struct PeripheralDisp: Hashable {
    let serialNo: Int
    let displayName: String
}

class BLEManager: NSObject, ObservableObject, CBCentralManagerDelegate {
        
    @Published var isSwitchedOn = false
    @Published var peripheralsDisp = [PeripheralDisp]()

    var myCentral: CBCentralManager!
    var myPeripheral: CBPeripheral!
    
    override init() {
        super.init()
        
        myCentral = CBCentralManager(delegate: self, queue: nil)
        myCentral.delegate = self
    }
    
    func centralManagerDidUpdateState(_ central: CBCentralManager) {
        if central.state == .poweredOn {
            isSwitchedOn = true
            startScanning()
        }
        else {
            isSwitchedOn = false
            stopScanning()
        }
    }
    
    func centralManager(_ central: CBCentralManager, didDiscover peripheral: CBPeripheral, advertisementData: [String : Any], rssi RSSI: NSNumber) {
        
        var peripheralName: String = ""

        var peripheralSerialNo: Int = 0
        var peripheralDisplayName: String = ""
        
        if let name = advertisementData[CBAdvertisementDataLocalNameKey] as? String {
            peripheralName = name
        }
        else {
            peripheralName = "Unknown"
        }
                let newPeripheralDisp = PeripheralDisp(serialNo: newPeripheralDisp.count, displayName: peripheralDisplayName)
                peripheralsDisp.append(newPeripheralDisp) //peripheralDisplayName)

    }
    
    func startScanning() {
        print("StartScanning")
        myCentral.scanForPeripherals(withServices: nil, options: nil)
    }
    
    func stopScanning() {
        print("StopScanning")
        myCentral.stopScan()
    }
}

Full ContentView.swift:

struct ContentView: View {
    
    @EnvironmentObject var viewRouter: ViewRouter
    @ObservedObject var bleManager = BLEManager()
    @State var selectedDevice = 0
    
    var body: some View {
        
        
        VStack(spacing: 10) {
                        
            Spacer()
         
            // Device Picker
            Picker(selection: $selectedDevice, label: Text("")) {
                ForEach(self.bleManager.peripheralsDisp, id: \.self) { peripheral in
                    Text(peripheral.displayName)
                }
            }
            .frame(width: 200, height: 40, alignment: .center)
            

            /*List(bleManager.peripherals) { peripheral in
                Text(peripheral.displayName)
            }.frame(height: 300)
            
            Spacer()*/
            
         }
    }
}

Answer 1

There are a couple of issues here. First SwiftUI's ForEach behaves differently for static content and dynamic content. If you want your content to be dynamic, make your model conform to Identifiable and use the overload of ForEach that just takes a sequence of Identifiable . Second you are changing the list so its possible that the selection could change as items drop in an out. I suppose you could just reset the selection to 0 if the selected item is deleted. to do this you should move the selection into your ObservableObject and not your view. I actually think the conceptually simpler idea here is to use a list and not a picker. Just update the list and when they tap on an item you select it. (ie the list does not need to maintain the idea that some item is always selected while the picker does).