Swift

Building the log in interface

To be able to log in, you will need to add three elements to the screen:

A UIButton to log in Alice
A UIButton to log in Bob
A UILabel to show the connection status.

Open ViewController.swift and add it programmatically:

class ViewController: UIViewController {

    let loginAliceButton = UIButton(type: .system)
    let loginBobButton = UIButton(type: .system)
    let statusLabel = UILabel()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
        
        loginAliceButton.setTitle("Log in as Alice", for: .normal)
        loginAliceButton.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(loginAliceButton)
        
        loginBobButton.setTitle("Log in as Bob", for: .normal)
        loginBobButton.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(loginBobButton)
        
        statusLabel.text = ""
        statusLabel.textAlignment = .center
        statusLabel.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(statusLabel)
        
        NSLayoutConstraint.activate([
            loginAliceButton.centerYAnchor.constraint(equalTo: view.centerYAnchor),
            loginAliceButton.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            loginAliceButton.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
            loginAliceButton.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20),
            
            loginBobButton.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            loginBobButton.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
            loginBobButton.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20),
            loginBobButton.topAnchor.constraint(equalTo: loginAliceButton.bottomAnchor, constant: 20),
            
            statusLabel.centerXAnchor.constraint(equalTo: view.centerXAnchor),
            statusLabel.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
            statusLabel.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20),
            statusLabel.topAnchor.constraint(equalTo: loginBobButton.bottomAnchor, constant: 20)
        ])
    }
}