ios - How to change app color theme - ios

Question

Hi I'm new to ios dev and I'm trying to make buttons, which are in my 'settings viewController', change the color theme of the entire app (i.e. background color).
The code below is currently in the appDelegate class, as I found that it works great for this purpose.
So now I'm not sure how to have the buttons in my 'settings viewController' activate the code in the appDelegate. Should I be setting a listener for the event? use closures?
Any help is appreciated. please post code solutions if possible it really helps!:)
func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
UINavigationBar.appearance().tintColor = UIColor.whiteColor()
UINavigationBar.appearance().titleTextAttributes = [NSForegroundColorAttributeName:UIColor.whiteColor()]
Style.greenTheme()
}

Answer 1

The solution I use:
extension UIColor{
#nonobjc static var clr_blue: UIColor!
static func initWithColorScheme(cs: ColorScheme){
switch cs{
case .Default:
clr_blue = blueColor()
case .Custom:
clr_blue = UIColor(hue: 0.6, saturation: 0.85, brightness: 1, alpha: 1)
}
}
}
enum ColorScheme{
case Default, Custom
}
Create as many custom colours and colour schemes as you wish. Usage:
UIColor.clr_blue
But don't forget to initialize your UIColor inside application:didFinishLaunchingWithOptions: as follows: UIColor.initializeWithColorScheme(.Custom)
To change the colour scheme of a current UIViewController without need to restart, add this method to your UIViewController:
func changeSchemeTo(cs: ColorScheme){
UIColor.initializeWithColorScheme(cs)
for subview in self.view.subviews{
subview.setNeedsDisplay()
}
}

Answer 2

The appDelegate is specifically for setting options for the whole app. If you're wanting to do these things when a button is tapped, you'll simply want to add those lines of code into an IBAction for the button that's connected to your interface:
#IBAction func greenButtonTapped(sender: AnyObject) {
<#Code to be run when button tapped#>
}
Then just connect it to your UI element and you're all set.

Answer 3

So now I'm not sure how to have the buttons in my 'settings viewController' activate the code in the appDelegate
Code in application:didFinishLaunchingWithOptions: runs automatically when your app launches. Thus this is the right place for the appearance proxy to be configured. There is nothing to "activate".
If you run other code to set the appearance proxy later, be careful. This is not a normal thing to do. You cannot use the appearance proxy to change the way existing interface elements look. You will need to change the existing interface manually when your "theme" changes.