如何在UITextField中只允许数字和字母且不包含任何空格和8个字符

import UIKit

class ViewController: UIViewController, UITextFieldDelegate {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let textField = UITextField(frame: CGRect(x: 50, y: 100, width: 200, height: 30))
        textField.borderStyle = .roundedRect
        textField.delegate = self
        self.view.addSubview(textField)
    }
    
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        // 创建只允许数字和字母的正则表达式
        let regex = try! NSRegularExpression(pattern: "^[a-zA-Z0-9]*$", options: .anchorsMatchLines)
        let fullString = (textField.text ?? "") + string
        
        // 判断输入的字符是否符合要求
        if regex.firstMatch(in: fullString, options: [], range: NSRange(location: 0, length: fullString.count)) == nil {
            return false
        }
        
        // 判断输入的字符是否包含空格和8个字符
        if fullString.contains(" ") || fullString.count > 8 {
            return false
        }
        
        return true
    }
}