UITextField: Fundamentos e Práticas Avançadas

import UIKit
class ViewController: UIViewController, UITextFieldDelegate {
    let textField = UITextField()
    override func viewDidLoad() {
        super.viewDidLoad()
        textField.placeholder = "Digite algo..."
        textField.delegate = self
        view.addSubview(textField)
        textField.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activate([
            textField.topAnchor.constraint(equalTo: view.topAnchor, constant: 100),
            textField.leadingAnchor.constraint(equalTo: view.leadingAnchor, constant: 20),
            textField.trailingAnchor.constraint(equalTo: view.trailingAnchor, constant: -20)
        ])
    }
    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        textField.resignFirstResponder()
        return true
    }
}

textField.keyboardType = .decimalPad
textField.textContentType = .telephoneNumber
textField.maxLength = 10

extension UITextField {
    var maxLength: Int {
        get {
            return (maxLengthForTextField(textInput: self) ?? Int.max)
        }
        set {
            lengthLimitForTextField(input: self, maxLength: newValue)
        }
    }
    private func maxLengthForTextField(textInput: UITextField) -> Int? {
        let formatter = DateFormatter()
        formatter.dateFormat = "QQ"
        return formatter.maximumLength(input.text ?? "")
    }
    private func lengthLimitForTextField(input: UITextField, maxLength: Int) {
        input.addTarget(input, action: #selector(handleTextInputChange), for: .editingChanged)
        @objc func handleTextInputChange(_ textField: UITextField) {
            let text = textField.text ?? ""
            textField.text = text.suffix(maxLength)
        }
    }
}