Kotlin OOP Concepts

KOTLIN
OOP CONCEPTS
1. Classes & Objects
2. Constructors
3. Inheritance
4. Properties
5. Sealed Classes
6. Enums

Classes and Objects
• Classes : Blueprint of objects.
• Object : An entity having attributes(name,age) or behaviours or
instance of the class binding data and function together in the
single unit.
parrot2 = Parrot()
parrot2 is an instance of Parrot class

Classes
class Parrot{ /*...*/ }
• The class declaration consists of the class name, the class
header (specifying its type parameters, the primary constructor,
and some other things)
• Class body surrounded by curly braces.
• Both the header and the body are optional.
• If the class has no body, the curly braces can be omitted.

Constructors
• Constructor is often used to initialize class members.
• Every kotlin class has a default constructor available if no
constructor is defined.

Constructors
• Primary and Secondary
• Rules of Primary constructor:- 1. No body
2. The init block acts as the body
• Rules of Secondary constructor:- 1. Has a body
2. Body of constructor is called
after the init
block.

Primary Constructor
• Part of the class header, and it goes after the class name and optional type
parameters.
class Parrot(Name: String) { /*...*/ }
• Inside the primary constructor we cannot write any logic, and to write the logic
we use init blocks in kotlin.
• A Kotlin class can have only single primary constructor and as many init blocks
and secondary constructors as required.

Inheritance
• Inheritance : Deriving classes from an existing class.
• The child classes
• Derived using an existing class inherits the properties and implementations
from the parent class;
• So, we do not have to define the implementations of parent class again.
• Hence, inheritance helps us in reusing the existing code.
• By default, Kotlin classes are final – they can't be inherited. To make a class
inheritable, mark it with the open keyword:
open class Base // Class is open for
inheritance

Inheritance
Class Animal{
}
Class Dog{
Var color: String
Var breed: String
Fun bark() {
}
Fun sleep(){
}
}
Class Cat{
Var color: String
Var age: Int
Fun meow() {
}
Fun sleep(){
}
}
*See how to override methods

Interfaces
• Interfaces are a way of defining abstractions.
• An interface is a collection of method and property.

Properties
• Encapsulates a value or a behavior associated with an object of
that class and are mutable.
• Properties are declared using the val or var keyword.
class Address {
var name: String = "James"
var street: String = "Brown"
var city: String = "Helsinki"
}

Sealed Class
• Subclassed in the same file.
• Commonly used to represent restricted class hierarchies(Where a
value can have one of the limited set of types).
Ex: - Representing different types of errors:
➔ sealed class called AppError
➔ subclasses like NetworkError, DatabaseError, and
PermissionError to represent different types of errors that can
occur in your app.
sealed class IOError(): Error

Enum Class
• Represents a fixed set of values.
• Used to define a set of constants. (A situation that does not
change)
Ex:- Enum classes can be used to encapsulate related values
into a single type.
enum class Seasons{
SPRING, SUMMER, AUTUMN, WINTER }

Kotlin OOP Concepts

More Related Content

What's hot (20)

Similar to Kotlin OOP Concepts (20)

Recently uploaded (20)

Kotlin OOP Concepts