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
}
