ViewController.swift

import UIKit

class ViewController: UIViewController {
    
    private let imageView: UIImageView = {
        let imageView = UIImageView()
        imageView.contentMode = .scaleAspectFill
        imageView.backgroundColor = .white
        return imageView
    }()
    
    private let button : UIButton = {
        let button = UIButton()
        button.backgroundColor = .white
        button.setTitle("Random Photo Generator", for: .normal)
        button.setTitleColor(.black, for: .normal)
        return button
    }()
    
    private let label: UILabel = {
            let label = UILabel()
            label.textColor = .black
            label.textAlignment = .center
            label.text = "Created by Leon Tang"
            label.font = UIFont.systemFont(ofSize: 16, weight: .bold)
            return label
        }()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        view.backgroundColor = .systemPink
        view.addSubview(imageView)
        imageView.frame = CGRect(x: 0, y: 0, width: 300, height: 300)
        imageView.center = view.center
        
        view.addSubview(button)
        button.addTarget(self, action: #selector(didTapButton), for: .touchUpInside)
        
        getRandomPhoto()
    }
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        
        button.frame = CGRect(x: 30,
                              y: view.frame.size.height - 150 - view.safeAreaInsets.bottom,
                              width: view.frame.size.width - 60,
                              height: 55
        )
        
        label.frame = CGRect(x: 20,
                                y: view.frame.size.height - 80 - view.safeAreaInsets.bottom,
                                width: view.frame.size.width - 40,
                                height: 20)
       
    }
    
    @objc func didTapButton() {
        getRandomPhoto()
    }
    
    func getRandomPhoto() {
        let urlString = "https://picsum.photos/200/300"
        guard let url = URL(string: urlString) else {
            return
        }
        
        URLSession.shared.dataTask(with: url) { [weak self] data, response, error in
            guard let self = self,
                  error == nil,
                  let data = data,
                  let image = UIImage(data: data) else {
                return
            }
            
            DispatchQueue.main.async {
                self.imageView.image = image
            }
        }.resume()
    }
}