import Foundation

@objc protocol OptionalDelegate: class {
   @objc optional func doTheOptionalThing()
}

protocol NonOptionalDelegate: class {
   func doTheNonOptionalThing()
}

protocol MyProtocol: OptionalDelegate, NonOptionalDelegate {
    
}

extension OptionalDelegate where Self: MyProtocol {
   func doTheOptionalThing() {
      print("I am doing the OPTIONAL thing!")
   }
    
   func doTheNonOptionalThing() {
      print("I am doing the NON OPTIONAL thing!")
   }    
}

class TestWithoutOptionalImpl: NSObject, MyProtocol {
    
}

class TestWithOptionalImpl: NSObject, MyProtocol {
   func doTheOptionalThing() {
      print("I am doing the OPTIONAL thing by overwriting implemenation in class")
   }
}

class TestDelegator {
   weak var delegateOptional: OptionalDelegate?
   weak var delegateNonOptional: NonOptionalDelegate?   

   func goAhead(){
      guard let delegateOptional = delegateOptional else { return}
      delegateOptional.doTheOptionalThing?()
        
      guard let delegateNonOptional = delegateNonOptional else { return}
      delegateNonOptional.doTheNonOptionalThing()
   }
}

print("--- Testing direct invokation ---")
let testWithoutOptionalImpl = TestWithoutOptionalImpl()
testWithoutOptionalImpl.doTheOptionalThing()
testWithoutOptionalImpl.doTheNonOptionalThing()

print("--- Testing for indirection through property ---")
let testDelegator = TestDelegator()
testDelegator.delegateOptional = testWithoutOptionalImpl
// 1. Testing if the the instance is actually assigned
print("Do we have an instance stored in the property? -> \(testDelegator.delegateOptional)" )

// 2. Is not invoking doTheOptionalThing() 
testDelegator.delegateOptional?.doTheOptionalThing?()
testDelegator.delegateNonOptional = testWithoutOptionalImpl

// 3. Is not invoking doTheOptionalThing() 
testDelegator.goAhead()

print("--- Testing for indirection through property with a direct implementation in class ---")
let testWithOptionalImpl = TestWithOptionalImpl()
testDelegator.delegateOptional = testWithOptionalImpl
testDelegator.delegateNonOptional = testWithOptionalImpl
testDelegator.goAhead()

--- Testing direct invokation ---
I am doing the OPTIONAL thing!
I am doing the NON OPTIONAL thing!
--- Testing for indirection through property ---
Do we have an instance stored in the property? -> Optional(<main.TestWithoutOptionalImpl: 0x7fa13b600240>)
I am doing the NON OPTIONAL thing!
--- Testing for indirection through property with a direct implementation in class ---
I am doing the OPTIONAL thing by overwriting implemenation in class
I am doing the NON OPTIONAL thing!

--- Testing direct invokation ---
I am doing the OPTIONAL thing!
I am doing the NON OPTIONAL thing!
--- Testing for indirection through property ---
Do we have an instance stored in the property? -> Optional(<main.TestWithoutOptionalImpl: 0x7fa13b600240>)
I am doing the OPTIONAL thing!
I am doing the OPTIONAL thing!
I am doing the NON OPTIONAL thing!
--- Testing for indirection through property with a direct implementation in class ---
I am doing the OPTIONAL thing by overwriting implemenation in class
I am doing the NON OPTIONAL thing!