Inheritance in Swift

In Swift programming language, a class can inherit properties, methods and other characteristics from another class. Inheriting these properties and attributes from one class to another class is known as inheritance.

Sub class: The class which inherits the properties from other class is called child class or sub class.

Super class: The main class from where the subclass inherits the properties is known as parent class or super class.

Swift4 classes consist of superclass which calls and accesses methods, properties, functions and overriding methods. Property observers are used to add a property and modify the stored and computed property methods.

Syntax:

class class_name: Superclass_name 
{
// Definition of the class
}

Base Class

A Base Class is a class which does not inherit methods, properties or functions from another class.

Example

class StudentDetails {
   var stname: String!
   var mark1: Int!
   var mark2: Int!
   var mark3: Int!
   init(stname: String, mark1: Int, mark2: Int, mark3: Int) {
      self.stname = stname
      self.mark1 = mark1
      self.mark2 = mark2
      self.mark3 = mark3
   }
}
let stname = "Aryan"
let mark1 = 70
let mark2 = 80
let mark3 = 85
print(stname)
print(mark1)
print(mark2)
print(mark3)

Output:

Aryan
70
80

Here, class with classname StudentDetails is defined as a base class which contains student's name, and three subjects mark as mark1, mark2 and mark3. The 'let' keyword is used to initialize the value for the base class and base class value is displayed using 'print' function.

Subclass

The subclass inherits properties, methods and functions of its base class. To define a subclass ':' is used before the base class name.

Example

class Person {
 var firstName: String
 var lastName: String
let birthPlace: String

init(birthPlace: String) {
self.birthPlace = birthPlace
}
}
class Student: Person 
{
var school: String
}
let student = Student(birthPlace: "India")
student.lastName  = "Head"
student.firstName  = "Travis"
print(student.birthPlace)
print(student.firstName)
print(student.lastName)

Output:

India
Travis
Head

Overriding

Overriding is used to access the super class instance, type methods, instance, type properties and subscripts. It uses a keyword 'override' to override the methods declared in the superclass.