Playing around with generics

Generics.swift

class ViewController: UIViewController {
  override func viewDidLoad() {
    super.viewDidLoad()
    
    let observer = NumberGeneratorObserver()
    observer.generatedNumber = { (number) in
      print("Observed: \(number)")
    }
    let generator = NumberGenerator()
    generator.addObserver(observer)
    generator.generate()
    generator.removeObserver(observer)
    generator.generate()
  }
}

// MARK: - Number Generator (Observable Example)

class NumberGenerator {
  private var observable = Observerable<NumberGeneratorObserver>()
  
  func generate() {
    notifyObserversOfNewNumber(7)
  }
  
  func addObserver(observer: NumberGeneratorObserver) {
    observable.add(observer)
  }
  
  func removeObserver(observer: NumberGeneratorObserver) {
    observable.remove(observer)
  }
  
  private func notifyObserversOfNewNumber(number: Int) {
    for observer in observable.observers {
      observer.generatedNumber?(number)
    }
  }
}

class NumberGeneratorObserver: Observer {
  var generatedNumber: ((Int) -> ())?
  
  func isEqualTo(other: Observer) -> Bool {
    return ObjectIdentifier(self) == ObjectIdentifier(other)
  }
}


// MARK: - Generic Observer

protocol Observer: class {
  func isEqualTo(other: Observer) -> Bool
}

class Observerable<T: Observer> {
  var observers = [T]()
  func add(observer: T) {
    observers.append(observer)
  }
  
  func remove(observerToRemove: T) {
    if let index = findIndex(observers, observerToRemove) {
      observers.removeAtIndex(index)
    }
  }
  
  private func findIndex<T: Observer>(array: [T], _ valueToFind: T) -> Int? {
    for (index, value) in array.enumerate() {
      if value.isEqualTo(valueToFind) {
        return index
      }
    }
    return nil
  }
}