LeeKahSeng

struct User: Codable {
    var firstName: String
    var lastName: String
    var lastLogin: Date?
}

@propertyWrapper
struct Storage<T: Codable> {
    private let key: String
    private let defaultValue: T

LeeKahSeng

struct AppData {
    
    @Storage(key: "enable_auto_login_key", defaultValue: false)
    static var enableAutoLogin: Bool
    
    @Storage(key: "username_key", defaultValue: "")
    static var username: String
}

LeeKahSeng

struct AppData {
    
    private static let enableAutoLoginKey = "enable_auto_login_key"
    private static let usernameKey = "username_key"
    
    static var enableAutoLogin: Bool {
        get {
            // Read from UserDefaults
            return UserDefaults.standard.bool(forKey:enableAutoLoginKey)
        }

LeeKahSeng

class Boy {
    
    // Failable initialisation
    init?(age: Int) {
        // Age cannot be less than 0
        if age < 0 {
            return nil
        }
    }
}

LeeKahSeng

let str: String? = "test"

// Optional binding using 'if'
if let value = str {
    print(value)
}


// Optional binding using guard
guard let value = str else {

LeeKahSeng

// Create another bird array that accept nil value
let otherBirds: [Bird?] = [chicken, nil]
let chicken4 = otherBirds[0] as? Chicken? // Cast successful: chicken4 type is Chicken??
let chicken5 = otherBirds[0] as! Chicken? // Cast successful: chicken5 type is Chicken?

let chicken6 = otherBirds[1] as? Chicken? // Cast failed: Trigger runtime error
let chicken7 = otherBirds[1] as! Chicken? // Cast failed: Trigger runtime error

let chicken8 = otherBirds[0] as? Chicken! // chicken8 type is Chicken?? | Warning: Using '!' here is deprecated and will be removed in a future release
let chicken9 = otherBirds[0] as! Chicken! // chicken9 type is Chicken? | Warning: Using '!' here is deprecated and will be removed in a future release

LeeKahSeng

class Bird {
    var name: String
    init(name: String) {
        self.name = name
    }
}

class Chicken: Bird {
    let canFly = false
}

LeeKahSeng

import Foundation
import CoreData
import UIKit

@objc(TestEntity)
public class TestEntity: NSManagedObject {
    
    @NSManaged private var base64: String
    var image: UIImage {
        set {

LeeKahSeng

import Foundation
import CoreData

extension TestEntity {

    @nonobjc public class func fetchRequest() -> NSFetchRequest<TestEntity> {
        return NSFetchRequest<TestEntity>(entityName: "TestEntity")
    }
}

LeeKahSeng

import Foundation
import CoreData
import UIKit

@objc(TestEntity)
public class TestEntity: NSManagedObject {
    
    var image: UIImage {
        set {
            base64 = base64(from: image)