我正在跟着Udemy的课程做一个简易Instagram克隆项目，现在遇到了一个运行时崩溃问题，希望能得到大家的帮助。

环境信息 #

• Xcode版本：14.2
• macOS版本：Monterey 12.6.5
• iOS模拟器版本：16.2

错误详情 #

当我点击登录界面底部的**"Don't have an account? Sign Up"**按钮时，App直接崩溃，控制台抛出以下错误：

Thread 1: "+[InstagramFirestoreTutorial.LoginController presentRegistrationController]: unrecognized selector sent to class 0x10b086788"

错误指向LoginController里尝试跳转注册页面的方法，代码位置在第118行：

@objc func presentRegistrationController() {
    let registrationController = RegistrationController()
    navigationController?.pushViewController(registrationController, animated: true)
}

相关代码 #

LoginController.swift

//
//  LoginController.swift
//  InstagramFirestoreTutorial
//
//  Created by *** on 27/02/2023.
//

import UIKit

class LoginController: UIViewController {

// MARK: - Class Properties

private let iconImageView: UIImageView = {
    let imageView = UIImageView(image: UIImage(named: "Instagram_logo_white")!)
    imageView.contentMode = .scaleAspectFill
    imageView.translatesAutoresizingMaskIntoConstraints = false
    return imageView
}()

private let emailTextField: CustomTextField = {
    let textField = CustomTextField(placeholder: "Email")
    textField.keyboardType = .emailAddress
    return textField
}()

private let passwordTextField: CustomTextField = {
    let textField = CustomTextField(placeholder: "Password")
    textField.isSecureTextEntry = true
    return textField
}()

private lazy var stackView: UIStackView = {
    let stackView = UIStackView(arrangedSubviews: [emailTextField, passwordTextField, logInButton, passwordRetrievalButton])
    stackView.axis = .vertical
    stackView.spacing = 20
    stackView.translatesAutoresizingMaskIntoConstraints = false
    return stackView
}()

private let logInButton: UIButton = {
    let button = UIButton(type: .system)
    button.setTitle("Log In", for: .normal)
    button.setTitleColor(.white, for: .normal)
    button.titleLabel?.font = UIFont.boldSystemFont(ofSize: 20.0)
    button.backgroundColor = UIColor(named: "logInButton")
    button.layer.cornerRadius = 5.0
    button.setHeight(50.0)
    button.translatesAutoresizingMaskIntoConstraints = false
    return button
}()

private let inviteRegistrationButton: UIButton = {
    let button = UIButton(type: .system)
    button.setAttributedTitle(withQuestion: "Don't have an account?", andAction: "Sign Up")
    button.addTarget(LoginController.self, action: #selector(presentRegistrationController), for: .touchUpInside)
    return button
}()

private let passwordRetrievalButton: UIButton = {
    let button = UIButton(type: .system)
    button.setAttributedTitle(withQuestion: "Forgotten your password?", andAction: "Get help logging in")
    return button
}()

// MARK: - Class Lifecycle Methods

override func viewDidLoad() {
    super.viewDidLoad()
    configureUI()
}

// MARK: - Class Supplementary Methods

private func configureUI() {
    view.backgroundColor = .white
    navigationController?.navigationBar.isHidden = true
    navigationController?.navigationBar.barStyle = .black
    configureGradientLayer()
    configureSubviews()
}

private func configureSubviews() {
    view.addSubview(iconImageView)
    NSLayoutConstraint.activate([
        iconImageView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
        iconImageView.heightAnchor.constraint(equalToConstant: 80.0),
        iconImageView.widthAnchor.constraint(equalToConstant: 120.0),
        iconImageView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 32.0)
    ])

    view.addSubview(stackView)
    NSLayoutConstraint.activate([
        stackView.topAnchor.constraint(equalTo: iconImageView.bottomAnchor, constant: 32.0),
        stackView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 32.0),
        stackView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -32.0)
    ])

    view.addSubview(inviteRegistrationButton)
    NSLayoutConstraint.activate([
        inviteRegistrationButton.centerXAnchor.constraint(equalTo: view.centerXAnchor),
        inviteRegistrationButton.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor)
    ])
}

// MARK: - Button Action Selector Functions

@objc func presentRegistrationController() {
    let registrationController = RegistrationController()
    navigationController?.pushViewController(registrationController, animated: true)
}

}

RegistrationController.swift

//
//  RegistrationController.swift
//  InstagramFirestoreTutorial
//
//  Created by **** on 27/02/2023.
//

import UIKit

class RegistrationController: UIViewController {

// MARK: - Class Properties

private let profilePhotoButton: UIButton = {
    let button = UIButton(type: .system)
    button.setImage(UIImage(named: "plus_photo"), for: .normal)
    button.tintColor = .white
    button.translatesAutoresizingMaskIntoConstraints = false
    return button
}()

private let emailTextField: CustomTextField = {
    let textField = CustomTextField(placeholder: "Email")
    textField.keyboardType = .emailAddress
    return textField
}()

private let passwordTextField: CustomTextField = {
    let textField = CustomTextField(placeholder: "Password")
    textField.isSecureTextEntry = true
    return textField
}()

private let fullnameTextField = CustomTextField(placeholder: "Fullname")

private let usernameTextField = CustomTextField(placeholder: "Username")

private let signUpButton: UIButton = {
    let button = UIButton(type: .system)
    button.setTitle("Sign Up", for: .normal)
    button.setTitleColor(.white, for: .normal)
    button.titleLabel?.font = UIFont.boldSystemFont(ofSize: 20.0)
    button.backgroundColor = UIColor(named: "signUpButton")
    button.layer.cornerRadius = 5.0
    button.setHeight(50.0)
    button.translatesAutoresizingMaskIntoConstraints = false
    return button
}()

private lazy var stackView: UIStackView = {
    let stackView = UIStackView(arrangedSubviews: [emailTextField, passwordTextField, fullnameTextField, usernameTextField, signUpButton])
    stackView.axis = .vertical
    stackView.spacing = 20
    stackView.translatesAutoresizingMaskIntoConstraints = false
    return stackView
}()

private let inviteToLogInButton: UIButton = {
    let button = UIButton(type: .system)
    button.setAttributedTitle(withQuestion: "Already have an account?", andAction: "Log In")
    button.addTarget(RegistrationController.self, action: #selector(presentLogInController), for: .touchUpInside)
    return button
}()

// MARK: - Class Lifecycle Methods

override func viewDidLoad() {
    super.viewDidLoad()
    configureUI()
}

// MARK: - Class Supplementary Methods

private func configureUI() {
    configureGradientLayer()
    addUISubviews()
    navigationController?.navigationBar.isHidden = true
}

private func addUISubviews() {
    view.addSubview(profilePhotoButton)
    NSLayoutConstraint.activate([
        profilePhotoButton.centerXAnchor.constraint(equalTo: view.centerXAnchor),
        profilePhotoButton.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 32.0),
        profilePhotoButton.widthAnchor.constraint(equalToConstant: 140.0),
        profilePhotoButton.heightAnchor.constraint(equalToConstant: 140.0)
    ])

    view.addSubview(stackView)
    NSLayoutConstraint.activate([
        stackView.topAnchor.constraint(equalTo: profilePhotoButton.bottomAnchor, constant: 32.0),
        stackView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 32.0),
        stackView.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -32.0)
    ])

    view.addSubview(inviteToLogInButton)
    NSLayoutConstraint.activate([
        inviteToLogInButton.centerXAnchor.constraint(equalTo: view.centerXAnchor),
        inviteToLogInButton.bottomAnchor.constraint(equalTo: view.safeAreaLayoutGuide.bottomAnchor)
    ])
}

@objc func presentLogInController() {
    navigationController?.popViewController(animated: true)
}

}

我尝试过的临时解决方法 #

我发现如果把inviteRegistrationButton的addTarget参数里的LoginController.self换成self，App就能正常跳转了，但Xcode会弹出一个警告。我不太理解为什么原来的写法会触发崩溃，也想知道怎么才能正确处理这个问题，既解决崩溃又消除警告。

（登录界面截图：[登录界面]）

备注：内容来源于stack exchange，提问作者IsaacNewtonGravity