Delegation Pattern

Question 1

The delegation pattern is a variation of another pattern known as:

Answer 1

Decorator

Question 2

Why do we specify the delegate’s type as a protocol?

Answer 2

To restrict only the objects that conform to the protocol from being assigned to the delegate property

Question 3

TF: A design pattern is a general, reusable solution to a commonly occurring problem within a given context, regardless of the particular domain.

Answer 3

True

Question 4

Generally, why should the delegate property be marked as weak?

Answer 4

To prevent reference cycles when the delegate and owner reference each other

Question 5

TF: A design pattern is a code snippet that you can add to your project.

Answer 5

False

Question 6

What is the base class for all objective c classes?

Answer 6

NSObject

Question 7

TF: You can assign a delegate both in code and in Interface Builder

Answer 7

True

Question 8

Why can we not implement optional protocol requirements?

Answer 8

Optional protocol requirements are an objective c construct and are currently unavailable in Swift

Question 9

What problems does delegation solve?

Answer 9

Avoiding tight coupling of objects 
Modifying behavior and appearance without the need to subclass objects
Allowing tasks to be handed off to an arbitrary object.

Question 10

What exactly is a design pattern?

Answer 10

A design pattern is a general, reusable solution to a commonly occurring problem within a given context, regardless of the particular domain.

Question 11

What the purpose of using a delegate? Example

Answer 11

Delegation is a design pattern that enables a class or structure to hand off (or delegate) some of its responsibilities to an instance of another type.

protocol HorseRaceDelegate: class {
    func race(_ race: Race, didStartAt time: Date)
    func addLapLeader(_ horse: Horse, forLap lap: Int, atTime time: Date)
    func race(_ race: Race, didEndAt time: Date, withWinner winner: Horse)
}

class Race {
    weak var delegate: HorseRaceDelegate?

func updateLeader() {
	delegate?.addLapLeader(horse, forLap: horse.currentLap, atTime: Date())

}
}