How to create a class and subclass in Swift

Creating a class in swift

A class is a user-defined data type that includes local methods and properties. It’s a blueprint to create objects.

Classes are an important concept in object-oriented programming. A class contains both data (variables) called properties and methods (functions defined inside a class).

We use the keyword class to define a class in Swift.

Syntax

class className{
  // methods, variables
}

Example

class Person {
  var name:String
  var age:Int
  init(name:String, age:Int){
    self.name = name
    self.age = age
  }
}
let person = Person(name: "john",  age: 23)
print("Person(name:\(person.name), age:\(person.age))")

Explanation

  • Lines 1–9: We create a class Person that has two members, name and age. We use the initializer init() method to initialize the values of the members name and age.
  • Line 11: An instance of the Person class is created with name as john and age as 23.
  • Line 12: We can access the properties using the dot (.) notation. The values of the variables of the person object are printed.

Creating a subclass in Swift

Inheritance in object-oriented programming is the ability of a class to derive or inherit methods and properties from another class. There are two types of categories of classes that involve​ inheritance:

  • Base class or parent class: A class whose properties are inherited by the derived class.
  • Derived class or subclass or child class: A class that inherits properties from another class.

Syntax

In Swift, we use the colon : to inherit a class from another class.

class ChildClass: BaseClass {
   // methods, variables
}

Example

class Vehicle {
  var brandName: String = "Ferrari"
  func honk(){
    print("Honking")
  }
}
class Car: Vehicle{
  var model: String = "Daytona"
  func display(){
    print("Car[brand=\(brandName), model=\(model)")
  }
}
let car = Car()
car.display()
car.honk()

Explanation

  • Lines 1–7: A Vehicle class is defined that has the attribute brandName and the method honk().
  • Lines 9–19: A Car class is defined that inherits from Vehicle class. It has its own attributes and methods.
  • Line 17: An instance of the Car class called car is created.
  • Line 18: The display() method of the Car class is invoked.
  • Line 19: The honk() method of the Vehicle class is invoked on the car instance as the Car class inherits from the Vehicle class.
Free AI Mock Interviews
Coding Interview
Coding PatternsFree Interview
Gain insights and practical experience with coding patterns through targeted MCQs and coding problems, designed to match and challenge your expertise level.
System Design
You TubeFree Interview
Learn to design a video streaming platform like YouTube by tackling functional and non-functional requirements, core components, and high-level to detailed design challenges.

Free Resources

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)