Swift Optionals Cheat Sheet

var name: String? = "Swift"   // may hold a String or nilname = nil                     // valid, since it's optionalvar age: Int = 30              // non-optional, cannot be nil// age = nil                   // compile error// Force unwrap with ! -- crashes at runtime if nillet forced: String = name!

var nickname: String? = "Swifty"// if let: unwraps only if non-nil, scoped to the if blockif let nickname = nickname {    print("Hello, \(nickname)")} else {    print("No nickname")}// Swift 5.7+ shorthand: `if let nickname` reuses the same nameif let nickname {    print("Hello, \(nickname)")}// guard let: unwraps or exits the current scope earlyfunc greet(_ nickname: String?) {    guard let nickname else {        print("No nickname provided")        return    }    print("Hello, \(nickname)") // nickname is non-optional here}// while let: loop while unwrapping succeedsvar stack = [1, 2, 3]while let top = stack.popLast() {    print(top)}

struct Address { var city: String? }struct Person { var address: Address? }let person = Person(address: Address(city: nil))// Optional chaining: returns nil if any link in the chain is nillet city: String? = person.address?.city// Nil-coalescing operator: provide a default for a nil optionallet displayCity = person.address?.city ?? "Unknown"// Chaining with method callslet uppercased = person.address?.city?.uppercased() ?? "N/A"

// Implicitly unwrapped optional: behaves like a non-optional at use sites,// but can still be nil and crashes if accessed while nil.var window: UIWindow!// Common for properties set immediately after init (e.g. IBOutlets)class ViewController: UIViewController {    @IBOutlet var titleLabel: UILabel! // set by Interface Builder before use}// Prefer regular optionals or ensuring init sets the value directly// wherever possible -- implicitly unwrapped optionals reintroduce crash risk.