Swift OOPs (Object-Oriented Programming)

What is OOP?

OOP (Object-Oriented Programming) is a programming paradigm that uses objects and classes to structure code. It helps in organizing complex programs, reusing code, and improving readability.

4 Main Pillars of OOP in Swift:

Encapsulation – Wrapping data and methods into a single unit (class).
Abstraction – Hiding complex implementation details and showing only necessary features.
Inheritance – Acquiring properties and methods from another class.
Polymorphism – Ability to use a function in different ways (overriding, overloading).

1. Classes and Objects in Swift

Class Syntax

class Person {
     var name: String
     var age: Int

     init(name: String, age: Int) {
         self.name = name
         self.age = age
     }

     func greet() {
         print( "Hello, my name is \(name). I am \(age) years old.")
     }
}

let person1 = Person( name: "John", age: 25)
person1.greet()

Output

Hello, my name is John. I

2. Encapsulation in Swift

Private, Public, Internal access control to restrict access to data.

class BankAccount {
     private var balance: Double = 0.0

     func deposit(amount: Double) {
         balance += amount
     }

     func getBalance() -> Double {
         return balance
     }
}

let account = BankAccount()
account.deposit(amount: 1000)
print(account.getBalance())

Output

1000.0

3. Inheritance in Swift

One class (child) can inherit properties and methods from another (parent).

class Vehicle {
     var brand: String

     init(brand: String) {
         self.brand = brand
     }

     func honk() {
         print("Beep! Beep!")
     }
}

class Car: Vehicle {
     var model: String

     init(brand: String, model: String) {
         self.model = model
         super.init(brand: brand)
     }

     func display() {
         print("Brand: \(brand), Model: \(model)")
     }
}

let car1 = Car(brand: "Toyota", model: "Corolla")
car1.honk() // Output: Beep! Beep!
car1.display()

Output

Beep! Beep!
Brand: Toyota, Model: Corolla

4. Polymorphism in Swift

Method Overriding

class Animal {
     func sound() {
         print("Animal sound")
     }
}

class Dog: Animal {
     override func sound() {
         print("Bark")
     }
}

let dog = Dog()
dog.sound() // Output: Bark

Output

Bark

5. Abstraction in Swift using Protocols

Protocol defines a blueprint of methods and properties.

protocol Drawable {
     func draw()
}

class Circle: Drawable {
     func draw() {
         print("Drawing a circle")
     }
}

class Square: Drawable {
     func draw() {
         print("Drawing a square")
     }
}

let shapes: [Drawable] = [Circle(), Square()]
for shape in shapes {
     shape.draw()
}

Output

Drawing a circle
Drawing a square

6. Access Modifiers in Swift

Modifier	Access Level
`open`	Accessible and subclassable anywhere
`public`	Accessible anywhere
`internal`	Accessible within same module/project
`fileprivate`	Accessible within same file
`private`	Accessible within same class/struct/extension