Programming in Swift: Functions & Types

Jan 4 2022 Swift 5.5, iOS 15, Xcode 13

Part 5: Protocols & Inheritance

38. Inheritance

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Previous episode: 37. Introduction Next episode: 39. Challenge: Inheritance

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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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In the Swift Fundamentals course you learned some distinguishing characteristics between classes and structures: classes are reference types, and structures are value types.

48 class Student: Person {

48 class Student: Person {
  var grades: [Grade] = []
}

52 let jon = Person(firstName: "Jon", lastName: "Snon")

53 let jane = Student(firstName: "Jane", lastName: "Snane")

55 jon.firstName
jane.firstName

let historyGrade = Grade(letter: "B", points: 9, credits: 3)
jane.grades.append(historyGrade)

61 jon.grades

61 class SchoolBandMember: Student {
 }

62 var minimumPracticeTime = 2

class StudentAthlete: Student {
}

class StudentAthlete: Student {
  66 var isEligible: Bool {
    return grades.filter { $0.letter == "F" } .count < 3
  }
}

75 let jessy = SchoolBandMember(firstName: "Jessy", lastName: "Catterwaul")

let marty = StudentAthlete(firstName: "Marty", lastName: "McWolf") 

74 let array = [jon, jane, jessy, marty]

74 let array: [Student] = …

74 … = [jane, jessy, marty]

let array = 

76 let student = marty as Student

77 let athlete = student as! StudentAthlete

77 … student as! SchoolBandMember

79 func getEveningActivity(student: Student) -> String {

}

80 if let bandMember = student as? SchoolBandMember {
    
  } else {
    return "Hitting the books!"
  }

81 return "Practicing for at least \(bandMember.minimumPracticeTime) hours."

getEveningActivity(student: jessy)
getEveningActivity(student: jane)

70 gr

70 override var grades: [Grade]

70  override var grades: [Grade] {
    get {  }
    set {
    
    }
}

get { return super.grades }

set {
73      super.grades = newValue
}

74 if !isEligible {
        print("It's time to study!")
      }

89 let utterFailureGrade = Grade(letter: "F", points: 0, credits: 0)

90 athlete.grades.append(utterFailureGrade)

91 athlete.grades.append(utterFailureGrade)

92 athlete.grades.append(utterFailureGrade)

70 override var grades: [Grade] {
    didSet {
      if !isEligible {
        print("It's time to study!")
      }
    }
  }