Programming in Swift: Functions & Types

Jan 4 2022 · Swift 5.5, iOS 15, Xcode 13

Part 5: Protocols & Inheritance

43. Protocols & Extensions

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Notes: 43. Protocols & Extensions

Update Notes: This course was originally recorded in 2019. It has been reviewed and all content and materials updated as of October 2021.

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We’ve gone over how inheriting from a class is different than adopting a protocol. But it’s possible for a protocol to inherit from another protocol. And as we’ll see in a moment, unlike with superclasses, a protocol can inherit from more than one other protocol.

protocol AloofAnimal: Animal { }

42 extension AloofAnimal {
 
 }

43 func speak() {
    print("My name is \(name). Please leave me alone. I must look at this wall.")
  }

74 Cat: AloofAnimal {

74 Cat: AloofAnimal { }

40 protocol Aloof {
  
}

41 var name: String { get }

44 extension Aloof {
  var greeting: String {
    
  }
}

46 return "My name is \(name). Please leave me alone."

50 protocol AloofAnimal: Aloof, Animal { }

54 print("\(greeting) I must look at this wall.")

class Cat {
  let name: String
  
  required init(name: String) {
    self.name = name
  }
}

extension Cat: AloofAnimal { }

func speak() {
  print(greeting + "Meow!")
}

extension Int {
  
}

func isEven(_ value: Int) -> Bool {
  value % 2 == 0
}
func isOdd(_ value: Int) -> Bool {
  (value + 1) % 2 == 0
}

var isEven(_ value: Int) -> Bool {
  value % 2 == 0
}
var isOdd(_ value: Int) -> Bool {
  (value + 1) % 2 == 0
}

var isEven😺:❌(_ value: Int) ->❌ Bool {
  value % 2 == 0
}
var isOdd😺:❌(_ value: Int) ->❌ Bool {
  (value + 1) % 2 == 0
}

var isEven😺:❌(_ value: Int) ->❌ Bool {
  self % 2 == 0
}
var isOdd😺:❌(_ value: Int) ->❌ Bool {
  (self + 1) % 2 == 0
}

5.isOdd
5.isEven

extension Numeric {

}

extension Numeric {
  var squared: Self {  }
}

extension Numeric {
  var squared: Self { self * self }
}

5.squared
5.5.squared

Time(day: .friday, hour: 17)

init(day: Weekday) {
  self.day = day
}

  var hour: UInt = 0
😺}

extension Time {🛑
  init(day: Weekday) {
    self.day = day
  }
}

Time()
Time(day: .wednesday)