Classes in Swift

Classes behave mostly the same as classes in JS or Ruby.

Use class keyword
Assign class properties within the block using let or var
Use init for initialize, deinit for any cleanup
Use func keyword for class methods
Use self to access class instances
Use the override keyword to override methods on the parent class

class Car {
  let name: String
  let year: Double
  var mpg: Float

  init(name: String, year: Double, mpg: Float) {
    self.name = name
    self.year = year
    self.mpg = mpg
  }

  func simpleDescription() -> String {
        return "This car mpg is \(self.mpg) miles per gallon"
    }

}

let volvo = Car(name: "xc60", year: 2023, mpg: 31.2)

print(volvo.name)
volvo.mpg = 30.0
print(volvo.simpleDescription())

You can also do OOP-ish class inheritence, by using the : operator, like a typedef.

class Vehicle {
  let wheels: Double
  init(wheels: Double) {
    self.wheels = wheels
  }

  func simpleDescription() -> String {
    return "This is a vehicle with \(self.wheels) wheels on it"
  }

}

class Car: Vehicle {
  let name: String
  let year: Double
  var mpg: Float

  init(name: String, year: Double, mpg: Float) {
    self.name = name
    self.year = year
    self.mpg = mpg
    super.init(wheels: 4)
  }

  override func simpleDescription() -> String {
        return "This car mpg is \(self.mpg) miles per gallon"
    }

}

let volvo = Car(name: "xc60", year: 2023, mpg: 31.2)

print(volvo.name)
volvo.mpg = 30.0
print(volvo.simpleDescription())

Other things about classes:

Class properties have getters and setters, as well as willSet and willGet hooks-like things.
Class properties can be public and private, and static. Same same.

Last modified: August 28, 2023