How to obatin the size of a View in SwiftUI

.overlay(GeometryReader { geo -> AnyView in
                    DispatchQueue.main.async{
                        self.displayWidth = geo.size.width
                        self.displayHeight = geo.size.height
                    }
                    return AnyView(EmptyView())
            })

struct ContentView: View {
    @State private var displayWidth: CGFloat = 0
    @State private var displayHeight: CGFloat = 0
    @State private var widthAndHeight = ""
    var body: some View {
        VStack {
            Text("Hello, world!")
                .padding()
                .overlay(GeometryReader { geo -> AnyView in
                    DispatchQueue.main.async{
                        displayWidth = geo.size.width
                        displayHeight = geo.size.height
                        widthAndHeight = geo.size.debugDescription
                    }
                    return AnyView(EmptyView())
            })
            Text("宽度：\(displayWidth)")
            Text("高度：\(displayHeight)")
            Text("宽高：\(widthAndHeight)")
        }
    }
}