既然是基于RxSwift，首先需要导入第三方库RxSwift,RxCocoa

extension Reactive where Base: UIButton {
    
    /* 
        button isEnable与否的两种情况下对应的 backgroudColor
     */
    
    public var isEnabledBgColor: UIBindingObserver<Base, Bool> {
        return UIBindingObserver(UIElement: self.base) { control, value in
            
            control.backgroundColor = value ? UIColor.blue : UIColor.white
        }
    }
    
    
    /*
     button isEnable与否的两种情况下对应的 borderColor
     */
    
    public var isEnabledBorderColor: UIBindingObserver<Base, Bool> {
        return UIBindingObserver(UIElement: self.base) { control, value in
            
            control.layer.borderColor = value ? UIColor.blue.cgColor : UIColor.white.cgColor
            control.layer.masksToBounds = true
            
        }
    }
}

以下举例如何调用

class RegisterViewController: UIViewController {
    @IBOutlet weak var phoneTextField: UITextField!
    @IBOutlet weak var authTextField: UITextField!
    @IBOutlet weak var passwordTextField: UITextField!
    @IBOutlet weak var showBt: UIButton!
    @IBOutlet weak var nextBt: UIButton!
    @IBOutlet weak var authBt: UIButton!
    
    var isCountDown = false
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let phoneValid = phoneTextField.rx.text.orEmpty
            .map{$0.count >= 11}
            .shareReplay(1)
        
        let borderValid = phoneTextField.rx.text.orEmpty
            .map{$0.count >= 11 && !(self.isCountDown)}
            .shareReplay(1)
        
        borderValid
            .bind(to: authBt.rx.isEnabled)
            .disposed(by: disposeBag)
        
        borderValid
            .bind(to: authBt.rx.isEnabledBorderColor)
            .disposed(by: disposeBag)
        
        phoneValid
            .bind(to: authBt.rx.isEnabledBgColor)
            .disposed(by: disposeBag)
        
}