gistfile1.txt

class ViewController: UIViewController {
	
  var customizerObject: SpecialProtocol? 
  
  override func viewDidLoad() {
		super.viewDidLoad()
		
		specialMethod()
		
	}

	func specialMethod() {
		// default
		if let c = customizerObject {
			c.specialMethod()
			return
		}
	}
	
}

protocol SpecialProtocol: class {
	func specialMethod()
}

class VCCustomizer: NSObject, SpecialProtocol {
	func specialMethod() {
		// Special implementation
	}
}