swift：取消绑定监听器数组的关闭监听器

Question

I am trying to develop a theme engine, which loads themes from a json . I have a Thememanager which is a singleton class and holds a currentTheme variable. I then have a baseViewController which listens to any change in the currentTheme with the help of Boxing technique, and all the viewControllers need to be subclass of base and need to override the observer method to apply their styles. In the box class I have an array of listeners so that multiple view controllers can observer theme change simultaneously, it works well and now my problem is that whenever a view controller gets deallocated , I want to remove that listener also from the box class array of listeners, which I am unable to figure out, because of which listeners are getting piled up.

I tried to write an unbind method in the deint of the viewController and tried to pass the closure like the below but it didnt work

func unbind(listener: Listener?) {

    self.listeners = self.listeners.filter { $0 as AnyObject !== listener as AnyObject }

}

Thememanager

class Thememanager {

    // Hold a list of themes
    var themes = [Theme]()
    // Private Init
    private init() {

        fetchMenuItemsFromJSON()
        // You can provide a default theme here.
        //change(theme: defaultTheme)
    }

    // MARK: Shared Instance

    private static let _shared = Thememanager()

    // MARK: - Accessors
    class func shared() -> Thememanager {
        return _shared
    }

    var currentTheme: Box<Theme?> = Box(nil)

    func change(theme: Theme) {

        currentTheme.value = theme
    }

    private func fetchMenuItemsFromJSON() {

        // TRIAL
        let theme = Theme()
        themes.append(theme)
    }
}

BOX

class Box<T> {

    typealias Listener = (T) -> Void
    var listeners = [Listener?]()

    var value: T {

        didSet {
            for listener in listeners{
                listener?(value)
            }
        }
    }

    init(_ value: T) {
        self.value = value
    }

    func bind(listener: Listener?) {

        self.listeners.append(listener)
        for listener in listeners{
            listener?(value)
        }
    }

    func unbind(listener: Listener?) {

        self.listeners = self.listeners.filter { $0 as AnyObject !== listener as AnyObject }

    }

}

BaseViewController

class BaseViewController: UIViewController {

    private var themeManager = Thememanager.shared()
    typealias Listener = (Theme?) -> Void
    var currentListener: Listener?
    override func viewDidLoad() {
        super.viewDidLoad()
        observeThemeChange()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    // Bind the theme variable so that changes are immediately effective
    func observeThemeChange() {
        currentListener = {[weak self] (theme) in
            guard let currtheme = theme else {
                return
            }
            self?.loadWith(theme: currtheme)
        }
        themeManager.currentTheme.bind(listener: currentListener)
    }

    // This method will be implemented by the Child classes
    func loadWith(theme: Theme) {

        self.navigationController?.navigationBar.tintColor = theme.navigationBarTextColor
        self.navigationController?.navigationBar.titleTextAttributes  = [NSAttributedStringKey.foregroundColor : theme.navigationBarTextColor]
        // Need to be implemented by child classes
        print("theme changed")
    }


    deinit {

        themeManager.currentTheme.unbind(listener: currentListener)
    }
}

Theme

struct Theme {

    // Define all the theme properties you want to control.

    var navigationBarBgColor: UIColor = UIColor.darkGray
    var navigationBarTextColor: UIColor = UIColor.black
}

Answer 1

The issue is with the comparison of closure in unbind method as it snot available for closures and functions(). See this . I guess you could maintain a hashmap where listeners be the value and a unique identifier be the key. It is going to be much faster to unbind it as well.

But, I feel Notifications way is much better as it gives you the same behaviour(Publisher-Subscriber) without you having to manage the listeners.