Study-Combine-Classic-Approach

import PlaygroundSupport
import UIKit

/// A line by line walk through of the following Combine example:
/// https://useyourloaf.com/blog/getting-started-with-combine/

class TermsOfUseViewController: UIViewController {
    
    // Some state:
    private var acceptedSwitch1: Bool = false {
        didSet { configureView() }
    }
    
    private var acceptedSwitch2: Bool = false {
           didSet { configureView() }
       }
    
    private var text: String = "" {
           didSet { configureView() }
       }
    
    let switch1: UISwitch = {
        let s = UISwitch()
        s.translatesAutoresizingMaskIntoConstraints = false
        s.layer.borderColor = UIColor.red.cgColor
        s.layer.borderWidth = 2.0
        return s
    }()
    
    let switch2: UISwitch = {
        let s = UISwitch()
        s.translatesAutoresizingMaskIntoConstraints = false
        s.layer.borderColor = UIColor.blue.cgColor
        s.layer.borderWidth = 2.0
        return s
    }()
    
    let textField: UITextField = {
        let tf = UITextField()
        tf.translatesAutoresizingMaskIntoConstraints = false
        tf.layer.borderColor = UIColor.green.cgColor
        tf.layer.borderWidth = 2.0
        return tf
    }()
    
    let button: UIButton = {
        let b = UIButton()
        b.translatesAutoresizingMaskIntoConstraints = false
        b.setTitle("Submit", for: .normal)
        b.setTitleColor(UIColor.blue, for: .normal)
        
        b.setTitleColor(UIColor.red, for: .disabled)
        
        return b
    }()
    
    override init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: Bundle?) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
        view.backgroundColor = UIColor.white
        
        // Setup actions
        switch1.addTarget(self, action: #selector(switch1Changed(_:)), for: .valueChanged)
        switch2.addTarget(self, action: #selector(switch2Changed(_:)), for: .valueChanged)
        textField.addTarget(self, action: #selector(textChanged(_:)), for: .editingChanged)
        button.addTarget(self, action: #selector(buttonTapped(_:)), for: .touchUpInside)
    }
    
    required init?(coder: NSCoder) {
        fatalError()
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()

        view.addSubview(switch1)
        view.addSubview(switch2)
        view.addSubview(textField)
        view.addSubview(button)
        
        setupConstraints()
        configureView()
    }
    
    func configureView() {
        print("configure view")
        button.isEnabled = (acceptedSwitch1 && acceptedSwitch2 && !text.isEmpty)
    }
    
    @objc private func switch1Changed(_ sender: UISwitch) {
        acceptedSwitch1 = sender.isOn
    }
    
    @objc private func switch2Changed(_ sender: UISwitch) {
        acceptedSwitch2 = sender.isOn
    }
    
    @objc private func textChanged(_ sender: UITextField) {
        text = sender.text ?? ""
    }
    
    @objc private func buttonTapped(_ sender: UIButton) {
        print("you tapped the button")
    }
    
    private func setupConstraints() {
        NSLayoutConstraint.activate([
            switch1.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            switch1.topAnchor.constraint(equalTo: view.topAnchor),
            view.trailingAnchor.constraint(equalTo: switch1.trailingAnchor),
            
            switch2.topAnchor.constraint(equalTo: switch1.bottomAnchor),
            switch2.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            view.trailingAnchor.constraint(equalTo: switch2.trailingAnchor),
            
            textField.topAnchor.constraint(equalTo: switch2.bottomAnchor),
            textField.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            view.trailingAnchor.constraint(equalTo: textField.trailingAnchor),
            textField.heightAnchor.constraint(equalToConstant: 44),
            
            button.topAnchor.constraint(equalTo: textField.bottomAnchor),
            button.leadingAnchor.constraint(equalTo: view.leadingAnchor),
            view.trailingAnchor.constraint(equalTo: button.trailingAnchor),
            button.heightAnchor.constraint(equalToConstant: 44)
        ])
    }
}

let vc = TermsOfUseViewController()

// reigns in the Keyboard
vc.preferredContentSize = vc.view.frame.size

PlaygroundPage.current.liveView = vc