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README.md	README.md

Initializer Questions 1 ~ 10

1) What is initializer?

Answer:

Initializer is a method that constructs the object with proper default values.

struct SomeStruct {

	init() {}

}

2) What are the different types of initializers available in Swift?

Answer:

Default
Customized
Convenience
Failable
Required

/*** Class & Struct Initializers ***/

// Default
struct SomeStruct {

	// init() {}

}

// Customized
struct SomeStructWithCustomization {

	let value1: String = "value"
	let value2: String

	init(value2: String) {
		self.value2 = value2
	}

	init(value1: String, value2: String) {
		self.value1 = value1
		self.value2 = value2
	}

}

// Convenience
struct SomeStructWithConvenience {
	let value1: String
	let value2: String

	init(value1: String, value2: String) {
		self.value1 = value1
		self.value2 = value2
	}

	// Convenience init
	// Convenience init should initialize `init(value1: String, value2: String)`
	// Why doing this? Because it can be convenient
	convenience init() {
		self.init(value1: "value1", value2: "value2")
	}

}

// Failable

// Required
protocol SomeStructProtocol {
	init(value1: String)
}

struct SomeStructWithRequiredInitializer: SomeStructProtocol {

	let value1: String

	required init(value1: String) {
		self.value1 = value1
	}

}

3) What is the default initializer in Swift?

Answer:

init is the default initializer in Swift.

struct SomeStruct {

	// init() {}

}

class SomeCalss {

	// init() {}

}

4) What is parameterized / Custom Initializer?

Answer:

init method with some input parameters to construct the object with custom values.

class Car {

	var model: Int = 0
	var speed: Int = 0
	var color: String = ""

	init() {
		self.model = 2022
		self.speed = 0
		self.color = "Red"
	}

	init(model: Int, color: String) {
		self.model = model
		self.speed = 0
		self.color = color
	}

}

let car: Car = Car()

print(car.color) // Red

let purpleCar: Car = Car(model: 2022, color: "Purple")

print(purpleCar.color) // Purple

5) What is designated initializer in Swift?

Answer:

Default init method is the designated initializer

6) What is convenience initializer in Swift?

Answer:

Convenience Initializer is a kind of initializer which sets custom values for a few properties of an Object. Use convenience keyword to create convenience initializer.
Designated initializer must be called before setting the custom values.

class Car {

	let model: Int
	let speed: Int
	let color: String

	init(model: Model, speed: Int, color: String) {
		self.model = model
		self.speed = speed
		self.color = color
  }

	//Convenience init must call `**Designated initializer`** first!
	convenience init(color: String) {
		init(model: 2022, speed: 80, color: color)
	}

}

let car: Car = Car(color: "Red")
print(car.model) // 2022

let newCar: Car = Car(model: 2024, speed: 120, color: "Blue")
print(car.model) // 2024

7) What is failable initializer in Swift?

Answer:

An initializer which may fail to construct Object, User init?(params) to create failable initializers.

class Car {
	var model: Int = 0
	var color: String = ""
	var numberOfGears: Int = 0

	init(price: Int) {
			if price < 0 {
				return nil
			}
			self.model = 2019
			self.color = "Blue"
			self.numberOfGears = 5
	}

}

8) Can I declare a convenience initializer without designated initializer?

Answer:

class Car {

	let model: Int
	let speed: Int
	let color: String

//	init(model: Int, speed: Int, color: String) {
//		self.model = model
//		self.speed = speed
//		self.color = color
//	}

	convenience init(color: String) {
		#warning("Compilation Error")
		self.init() // Cannot invoke 'Car.init'
		self.color = color
	}

}

9) What is deinit? Can we call deinit method?

Answer:

deinit is a method which gets called automatically when the object is getting cleaned from memory. Additionally, you can dispose any resources in deinit method.

class Car {

	let model: Int
	let speed: Int
	let color: String

	init(model: Int, speed: Int, color: String) {
		self.model = model
		self.speed = speed
		self.color = color
	}

	deinit {
		print("Clear Car Object From Memory")
	}

}

var car: Car? = Car(model: 2024, speed: 500, color: "Red")
car = nil // Clear Car Object From Memory

#warning("We cannot call deinit method")
car.deinit // not callable

10) Designated Initializer vs Convenience Initializer

Answer:

Designated initializer is common initializer which makes sure all properties of a class are assigned with proper values.
Convenience initializer calls designated initializer and makes sure all properties are initialized. hen the custom values will be assigned for some properties.

Section 1, Data Type

Section 2, Operator

Section 3, Conditional Statement

Section 4, Enum

Section 5, functions

Section 6, struct

Section 7, initializers

Section 8, closures

Section 9, OOP

Section 10, static type vs dynamic type

Section 11, optional

Section 12, generic