class Basics / init() / deinit()

class ClassName {
    // Stored property
    var property: Type

    // Initializer
    init(property: Type) {
        self.property = property
    }

    // Deinitializer (called when the instance is released)
    deinit {
        // Cleanup
    }

    // Method
    func methodName() {
        // Implementation
    }
}

class BankAccount {
    let owner: String
    var balance: Double

    init(owner: String, balance: Double) {
        self.owner = owner
        self.balance = balance
        print("Created account for \(owner)")
    }

    deinit {
        print("Released account for \(owner)")
    }

    func deposit(_ amount: Double) {
        balance += amount
        print("Deposited \(amount) → Balance: \(balance)")
    }

    func withdraw(_ amount: Double) -> Bool {
        if balance >= amount {
            balance -= amount
            print("Withdrew \(amount) → Balance: \(balance)")
            return true
        }
        print("Insufficient balance")
        return false
    }
}

// Create an instance
let alice = BankAccount(owner: "Alice", balance: 10000)
alice.deposit(5000)
alice.withdraw(3000)

// Reference type: both variables share the same instance
let sameAccount = alice
sameAccount.deposit(1000)
print("Alice's balance: \(alice.balance)")  // Reflects the change — same instance

// Use the identity operator to check if they are the same instance
print("Same instance: \(alice === sameAccount)")

let other = BankAccount(owner: "Bob", balance: 0)
print("Different instance: \(alice !== other)")

Because a class is a reference type, assigning it to another variable does not create a copy — both variables point to the same instance. This is the key difference from struct, which is a value type.

deinit is called automatically when the instance is removed from memory. Use it for cleanup tasks such as closing files or releasing resources. Classes support inheritance, but structs do not. When inheritance is not needed, preferring struct is idiomatic Swift.

For class inheritance, see Inheritance / override / final / super.