{"id":2744,"date":"2026-02-05T12:08:00","date_gmt":"2026-02-05T12:08:00","guid":{"rendered":"https:\/\/demo.materiamedica.net\/demo6\/?p=2744"},"modified":"2026-02-05T12:08:00","modified_gmt":"2026-02-05T12:08:00","slug":"chapter-79-swift-classes-objects","status":"publish","type":"post","link":"https:\/\/demo.materiamedica.net\/demo6\/chapter-79-swift-classes-objects\/","title":{"rendered":"Chapter 79: Swift Classes\/Objects"},"content":{"rendered":"1. What is a class? What is an object? (the clearest possible explanation)<\/h3>\n
Class<\/strong> = the blueprint<\/strong> \/ recipe<\/strong> \/ template<\/strong> Object<\/strong> = one actual thing made from that blueprint<\/p>\nReal-life analogy (the one that clicks for almost everyone):<\/p>\n
\n- Class<\/strong> = the design \/ blueprint of a smartphone (screen size, camera specs, battery type, how buttons work\u2026)<\/li>\n
- Object<\/strong> = one actual phone made from that blueprint \u2192 My iPhone 14 Pro \u2192 Your iPhone 15 \u2192 Your friend\u2019s iPhone 13<\/li>\n<\/ul>\n
Both phones follow the same design<\/strong> (same class), but each phone has its own:<\/p>\n\n- own phone number<\/li>\n
- own photos<\/li>\n
- own battery level<\/li>\n
- own wallpaper<\/li>\n<\/ul>\n
That is the core idea:<\/p>\n
Class<\/strong> defines what<\/strong> every object of that type knows and can do. Object<\/strong> is one concrete instance with its own specific values.<\/p>\n2. Creating a class \u2013 basic syntax<\/h3>\n\n
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class Person {\r\n \/\/ Properties (data)\r\n let name: String \/\/ cannot be changed after creation\r\n var age: Int \/\/ can be changed later\r\n var city: String? \/\/ optional \u2013 may be nil\r\n \r\n \/\/ Initializer (how to create an object)\r\n init(name: String, age: Int, city: String? = nil) {\r\n self.name = name\r\n self.age = age\r\n self.city = city\r\n }\r\n \r\n \/\/ Method (behavior)\r\n func introduce() {\r\n let cityText = city ?? \"somewhere\"\r\n print(\"Hi, I'm \\(name), \\(age) years old, from \\(cityText)\")\r\n }\r\n \r\n func haveBirthday() {\r\n age += 1\r\n print(\"Happy birthday! Now \\(name) is \\(age) years old \ud83c\udf82\")\r\n }\r\n}<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n3. Creating objects (instances) from the class<\/h3>\n\n
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Swift<\/div>\n
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\/\/ Create concrete objects\r\nlet rahul = Person(name: \"Rahul Verma\", age: 27, city: \"Bengaluru\")\r\nlet priya = Person(name: \"Priya Reddy\", age: 24)\r\n\r\n\/\/ Use them\r\nrahul.introduce() \/\/ Hi, I'm Rahul Verma, 27 years old, from Bengaluru\r\npriya.introduce() \/\/ Hi, I'm Priya Reddy, 24 years old, from somewhere\r\n\r\nrahul.haveBirthday() \/\/ Happy birthday! Now Rahul Verma is 28 years old \ud83c\udf82\r\n\r\n\/\/ rahul and priya are different objects\r\nprint(rahul.age) \/\/ 28\r\nprint(priya.age) \/\/ 24 (unchanged)<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\nImportant memory fact<\/strong>:<\/p>\n\n- rahul and priya are two separate objects<\/strong><\/li>\n
- Changing one does not affect<\/strong> the other<\/li>\n
- Classes are reference types<\/strong> \u2014 variables hold references<\/strong> (pointers) to the object in memory<\/li>\n<\/ul>\n
4. Real-life examples \u2014 classes you will actually write<\/h3>\nExample 1 \u2013 BankAccount (classic encapsulation example)<\/h4>\n\n
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Swift<\/div>\n
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class BankAccount {\r\n let accountNumber: String\r\n private var balance: Double = 0.0\r\n \r\n init(accountNumber: String, initialDeposit: Double) {\r\n self.accountNumber = accountNumber\r\n deposit(amount: initialDeposit)\r\n }\r\n \r\n var currentBalance: Double {\r\n balance\r\n }\r\n \r\n func deposit(amount: Double) {\r\n guard amount > 0 else {\r\n print(\"Deposit amount must be positive\")\r\n return\r\n }\r\n balance += amount\r\n print(\"Deposited \u20b9\\(amount). New balance: \u20b9\\(balance)\")\r\n }\r\n \r\n func withdraw(amount: Double) -> Bool {\r\n guard amount > 0 else {\r\n print(\"Withdrawal amount must be positive\")\r\n return false\r\n }\r\n guard amount <= balance else {\r\n print(\"Insufficient funds\")\r\n return false\r\n }\r\n \r\n balance -= amount\r\n print(\"Withdrew \u20b9\\(amount). New balance: \u20b9\\(balance)\")\r\n return true\r\n }\r\n}\r\n\r\n\/\/ Real usage\r\nlet savingsAccount = BankAccount(accountNumber: \"SB-123456\", initialDeposit: 25000)\r\nsavingsAccount.deposit(amount: 10000)\r\n_ = savingsAccount.withdraw(amount: 5000)\r\nprint(\"Current balance: \u20b9\\(savingsAccount.currentBalance)\")\r\n\/\/ savingsAccount.balance = -100000 \/\/ \u2190 compile error \u2013 private!<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\nExample 2 \u2013 Simple Car class (inheritance + polymorphism)<\/h4>\n\n
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Swift<\/div>\n
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class Car {\r\n let brand: String\r\n var currentSpeed: Double = 0.0\r\n \r\n init(brand: String) {\r\n self.brand = brand\r\n }\r\n \r\n func accelerate(to speed: Double) {\r\n currentSpeed = speed\r\n print(\"\\(brand) is now going at \\(speed) km\/h\")\r\n }\r\n \r\n func honk() {\r\n print(\"\\(brand) says: Beep beep!\")\r\n }\r\n}\r\n\r\nclass ElectricCar: Car {\r\n let batteryCapacity: Double\r\n \r\n init(brand: String, batteryCapacity: Double) {\r\n self.batteryCapacity = batteryCapacity\r\n super.init(brand: brand)\r\n }\r\n \r\n override func accelerate(to speed: Double) {\r\n super.accelerate(to: speed)\r\n print(\"Quiet electric acceleration \u2013 zero emissions!\")\r\n }\r\n \r\n override func honk() {\r\n print(\"\\(brand) says: Beep boop! (electric sound)\")\r\n }\r\n}\r\n\r\n\/\/ Polymorphism in action\r\nlet vehicles: [Car] = [\r\n Car(brand: \"Maruti Swift\"),\r\n ElectricCar(brand: \"Tata Nexon EV\", batteryCapacity: 40.5)\r\n]\r\n\r\nfor vehicle in vehicles {\r\n vehicle.accelerate(to: 80)\r\n vehicle.honk()\r\n}<\/code><\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n5. Very Common Beginner Mistakes & Correct Habits<\/h3>\n\n
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\n\n\n| Mistake<\/th>\n | Wrong \/ Risky code<\/th>\n | Correct \/ Better habit<\/th>\n | Why?<\/th>\n<\/tr>\n<\/thead>\n |
\n\n| Using var for everything<\/td>\n | var name: String everywhere<\/td>\n | Default to let unless you actually reassign<\/td>\n | let prevents accidental changes + better safety<\/td>\n<\/tr>\n |
\n| Force-unwrapping in class methods<\/td>\n | self.user!.name<\/td>\n | guard let user = user else { return }<\/td>\n | Safer, better error handling<\/td>\n<\/tr>\n |
\n| Deep inheritance hierarchies<\/td>\n | 5+ levels of inheritance<\/td>\n | Prefer composition or protocols<\/td>\n | Deep trees become hard to maintain<\/td>\n<\/tr>\n |
\n| Making everything public<\/td>\n | public class, public var everywhere<\/td>\n | Use internal (default) or private when possible<\/td>\n | Better encapsulation & API control<\/td>\n<\/tr>\n |
\n| Mutating shared state without care<\/td>\n | static var sharedBalance<\/td>\n | Prefer dependency injection over singletons<\/td>\n | Singletons make testing & reasoning hard<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/div>\n 6. Quick Summary \u2013 Classes vs Structs (the decision you make every day)<\/h3>\n\n \n \n\n\n| Feature \/ Question<\/th>\n | Class (reference type)<\/th>\n | Struct (value type)<\/th>\n | When most developers choose<\/th>\n<\/tr>\n<\/thead>\n | \n\n| Identity matters (same object, same instance)<\/td>\n | Yes \u2014 two variables can point to same object<\/td>\n | No \u2014 copying creates independent value<\/td>\n | Class when identity matters (shared state)<\/td>\n<\/tr>\n | \n| Inheritance supported<\/td>\n | Yes<\/td>\n | No<\/td>\n | Class when you need inheritance<\/td>\n<\/tr>\n | \n| Can be used as key in Dictionary\/Set<\/td>\n | No (unless you implement Hashable carefully)<\/td>\n | Yes (if Hashable)<\/td>\n | Struct almost always for value types<\/td>\n<\/tr>\n | \n| Memory management<\/td>\n | Reference counting (ARC)<\/td>\n | Copied on write (Copy-on-Write for Array, Dict\u2026)<\/td>\n | Struct safer for value semantics<\/td>\n<\/tr>\n | \n| Thread safety (mutable shared state)<\/td>\n | Can cause problems<\/td>\n | Safer (each copy independent)<\/td>\n | Struct preferred in modern Swift<\/td>\n<\/tr>\n | \n| Typical use in SwiftUI<\/td>\n | ObservableObject \/ @StateObject<\/td>\n | @State, @ObservedObject (structs)<\/td>\n | Structs for most data models<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/div>\n Modern Swift recommendation (2025\u20132026)<\/strong>:<\/p>\n\nUse struct<\/strong> by default for almost everything Use class<\/strong> only when you need:<\/p>\n\n- reference semantics (shared mutable state)<\/li>\n
- inheritance<\/li>\n
- Objective-C interop<\/li>\n
- identity comparison (===)<\/li>\n<\/ul>\n<\/blockquote>\n
7. Small Practice \u2013 Try these<\/h3>\n\n- Create a Person class with:\n
\n- let name: String<\/li>\n
- var age: Int<\/li>\n
- method haveBirthday() that increases age<\/li>\n<\/ul>\n<\/li>\n
- Create a BankAccount class like the example above\n
\n- private balance<\/li>\n
- deposit & withdraw methods<\/li>\n
- read-only currentBalance<\/li>\n<\/ul>\n<\/li>\n
- Create ElectricCar that inherits from Car\n
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