输入整数的iOS SwiftUI TextField缺少占位符

struct ContentView: View {
    @State private var inputText: String = ""
    
    var body: some View {
        VStack {
            TextField("请输入整数", text: $inputText)
                .padding()
                .overlay(
                    RoundedRectangle(cornerRadius: 5)
                        .stroke(Color.gray, lineWidth: 1)
                )
                .multilineTextAlignment(.center)
                .keyboardType(.numberPad)
                .onReceive(Just(inputText)) { newValue in
                    let filtered = newValue.filter { "0123456789".contains($0) }
                    if filtered != newValue {
                        self.inputText = filtered
                    }
                }
            
            Button("提交") {
                // 处理提交逻辑
            }
            .padding()
        }
        .padding()
    }
}