SMSのPINコード認証したりする感じのViewController

SMSVerificationViewController.swift

import UIKit
import RxSwift

final class SMSVerificationViewController: UIViewController {
    @IBOutlet weak var digits1TextField: UITextField!
    @IBOutlet weak var digits2TextField: UITextField!
    @IBOutlet weak var digits3TextField: UITextField!
    @IBOutlet weak var digits4TextField: UITextField!
    @IBOutlet weak var resendButton: UIButton!
    @IBOutlet weak var submitButton: UIButton!
    // swiftlint:disable implicitly_unwrapped_optional
    var phoneNumber: String!
    let pinCode: Variable<String?> = Variable<String?>(nil)
    let disposeBag = DisposeBag()

    static func make() -> SMSVerificationViewController {
        // swiftlint:disable force_unwrapping
        return R.storyboard.sMSVerification.instantiateInitialViewController()!
    }
}

// MARK: - lifecycles
extension SMSVerificationViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        self.digits.forEach { $0.delegate = self }

        pinCode.asDriver().distinctUntilChanged { a, b in
            if let a = a, let b = b {
                return a == b
            } else if a == nil && b == nil {
                return true
            }
            return false
        }.drive(onNext: { [weak self] code in
            if code != nil {
                self?.submitButton.isEnabled = true
            } else {
                self?.submitButton.isEnabled = false
            }
        }).addDisposableTo(self.disposeBag)
    }

    override func viewDidAppear(_ animated: Bool) {
        super.viewDidAppear(animated)

        self.updateStyles()
        self.firstEmptyTextField().becomeFirstResponder()
    }
}

// MARK: - UITextFieldDelegate
extension SMSVerificationViewController: UITextFieldDelegate {

    func textFieldDidBeginEditing(_ textField: UITextField) {
        let firstEmptyField = firstEmptyTextField()
        if let text = textField.text, textField != firstEmptyField && text.isEmpty {
            firstEmptyField.becomeFirstResponder()
            textField.resignFirstResponder()
        }
    }

    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        if textField.text == nil { return true }

        if string.isEmpty {
            self.setStyle(textField: textField, state: .empty)
            let emptifiedField = lastFulfilledTextField()
            emptifiedField.text = ""
            lastFulfilledTextField().becomeFirstResponder()
            self.pinCode.value = nil
        } else {
            let fulfilledField = firstEmptyTextField()
            fulfilledField.text = string

            if fulfilledField == digits4TextField {
                view.endEditing(true)
                fulfilledField.resignFirstResponder()
                self.onFullFilled()
            }
        }

        self.updateStyles()

        return false
    }
}

private extension SMSVerificationViewController {

    var digits: [UITextField] {
        return [
            digits1TextField,
            digits2TextField,
            digits3TextField,
            digits4TextField
        ]
    }

    func firstEmptyTextField() -> UITextField {
        for field in digits {
            if let text = field.text, text.isEmpty {
                return field
            }
        }
        return digits4TextField
    }

    func lastFulfilledTextField() -> UITextField {
        for field in digits.reversed() {
            if let text = field.text, !text.isEmpty {
                return field
            }
        }
        return digits1TextField
    }

    func onFullFilled() {
        let code = digits.map { $0.text ?? "" }.joined()
        if code.characters.count == 4 {
            pinCode.value = code
        }
    }

    func setStyle(textField: UITextField, state: EditState) {

        textField.textColor = .white
        textField.layer.borderWidth = 0.0
        textField.layer.borderColor = UIColor.black.cgColor
        textField.layer.backgroundColor = nil
        textField.layer.removeAllAnimations()
        textField.layer.cornerRadius = 5.0
        textField.layer.masksToBounds = false
        textField.layer.shadowOpacity = 0.0
        textField.layer.shadowRadius = 2.0
        textField.layer.shadowOffset = CGSize(width: 0.0, height: 0.0)

        let bgAnimation = CABasicAnimation(keyPath: "borderColor")
        let shadowColorAnimation = CABasicAnimation(keyPath: "shadowColor")
        let shadowOpacityAnimation = CABasicAnimation(keyPath: "shadowOpacity")

        bgAnimation.fromValue = textField.layer.backgroundColor
        shadowColorAnimation.fromValue = textField.layer.shadowColor
        shadowOpacityAnimation.fromValue = textField.layer.shadowOpacity

        let animations = CAAnimationGroup()
        animations.animations = [bgAnimation, shadowColorAnimation, shadowOpacityAnimation]
        animations.duration = 0.33
        animations.isRemovedOnCompletion = true
        animations.fillMode = kCAFillModeRemoved
        animations.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)

        switch state {
        case .empty:
            textField.layer.borderWidth = 0.0
            textField.layer.shadowColor = nil
            textField.layer.shadowOpacity = 0.0
        case .fulfilled:
            textField.layer.borderWidth = 1.0
            textField.layer.borderColor = UIColor.orange.cgColor
            textField.layer.shadowColor = UIColor.orange.cgColor
            textField.layer.shadowOpacity = 0.3
            bgAnimation.toValue = UIColor.orange.cgColor
            shadowColorAnimation.toValue = UIColor.orange.cgColor
            shadowOpacityAnimation.toValue = 0.3
            textField.layer.add(animations, forKey: "animations")
        case .focus:
            textField.layer.borderWidth = 1.0
            textField.layer.borderColor = UIColor.blue.cgColor
            textField.layer.shadowColor = UIColor.black.cgColor
            textField.layer.shadowOpacity = 0.3
            bgAnimation.toValue = UIColor.blue.cgColor
            shadowColorAnimation.toValue = UIColor.black.cgColor
            shadowOpacityAnimation.toValue = 0.3
            textField.layer.add(animations, forKey: "animations")
        }

    }

    func updateStyles() {
        digits.forEach { field in
            guard let text = field.text else { return }
            if text.isEmpty {
                self.setStyle(textField: field, state: .empty)
            } else {
                self.setStyle(textField: field, state: .fulfilled)
            }
        }
        let firstEmptyField = self.firstEmptyTextField()
        if let text = firstEmptyField.text, text.isEmpty {
            self.setStyle(textField: firstEmptyField, state: .focus)
        }
    }

    enum EditState: Int {
        case fulfilled = 0
        case empty
        case focus
    }

}