在SwiftUI for iOS中，如何检测TextField何时失去焦点？

import SwiftUI

struct ContentView: View {
    @State private var text: String = ""
    @FocusState private var isFocused: Bool
    
    var body: some View {
        VStack {
            TextField("请输入文本", text: $text)
                .textFieldStyle(RoundedBorderTextFieldStyle())
                .padding()
                .focused($isFocused)
            
            Button("提交") {
                isFocused = false
            }
        }
        .onSubmit {
            isFocused = false
        }
    }
}

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