我正在尝试将我的macOS应用程序的UI在StoryBoard中写入SwiftUI。我是SwiftUI的初学者...
我有swiftUI Picker如下：

import SwiftUI

struct MessageAreaView: View {

// opponent name
@ObservedObject var anOpponentName: ShareValues

// menu type picker selection
@State var selectedMenu: String = ""

// menu type picker content
let defaultMenus = ["Hi. How about a game?", "Good luck!", "I give in.", "Thank you for the game.", "Let’s play again sometime.", "My hand slipped. May I undo?", "Hello.", "Goodby.", "Thanks."]

var body: some View {

    // Menu type picker
    Picker(selection: $selectedMenu, label: Text(""), content: {
        Text("Select Item").tag("") // To avoid "picker: the selection "" is invalid..."
        ForEach(defaultMenus, id:\.self) { aMenu in
           Text(aMenu)
        }
    })
    .pickerStyle(.menu)
    .onChange(of: selectedMenu, perform: { selected in
                    
        if !(selected == NSLocalizedString("Select Item", comment: "Select Item")) {
            
            let anOpponent = anOpponentName.anOpponentName
            
            let commentToSend = NSString(format: "TELL %@ %@\r\n", anOpponent, selected) as String
            mySocket.sendMessage(message: commentToSend)
        }
        // I'd like to set selectedMenu to "Select Item" here...
    })
    .frame(width:470)
}

我想将selectedMenu设置为“Select Item”（选择器选择的第一项）。使用NSPopUpButton，有selectItem（位于：index），但是我在SwiftUI Picker中找不到这样做的方法...我该怎么做呢？