ContentView.swift

//
//  ContentView.swift
//  DemoHostingC
//
//  Created by Mohammad Azam on 4/18/20.
//  Copyright © 2020 Mohammad Azam. All rights reserved.
//

import SwiftUI

struct ContentView: View {
    var body: some View {
        Text(/*@START_MENU_TOKEN@*/"Hello, World!"/*@END_MENU_TOKEN@*/)
            .background(Color.green)
            
    }
}

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

ViewController.swift

//
//  ViewController.swift
//  DemoHostingC
//
//  Created by Mohammad Azam on 4/18/20.
//  Copyright © 2020 Mohammad Azam. All rights reserved.
//

import UIKit
import SwiftUI

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        
        let controller = UIHostingController(rootView: ContentView())
        controller.view.translatesAutoresizingMaskIntoConstraints = false
        self.addChild(controller)
        self.view.addSubview(controller.view)
        controller.didMove(toParent: self)
        
        NSLayoutConstraint.activate([
                   controller.view.widthAnchor.constraint(equalToConstant: 200),
                   controller.view.heightAnchor.constraint(equalToConstant: 44),
                   controller.view.centerXAnchor.constraint(equalTo: self.view.centerXAnchor),
                   controller.view.centerYAnchor.constraint(equalTo: self.view.centerYAnchor)
        ])

    }


}