如何在UIView中使SwiftUI视图透明或半透明？

SwiftUI {
    Text("Hello, World!")
        .opacity(0.5)
}

struct CustomView: UIViewRepresentable {
    func makeUIView(context: Context) -> UIView {
        let view = UIView()
        view.backgroundColor = UIColor.red.withAlphaComponent(0.5)
        return view
    }
    
    func updateUIView(_ uiView: UIView, context: Context) {
        
    }
}

struct ContentView: View {
    var body: some View {
        CustomView()
    }
}

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let view = UIView()
        view.backgroundColor = .green
        view.alpha = 0.7
        self.view.addSubview(view)
    }
}