Dasar

Hello World

import Foundation
print("Hello, World!")

Konstanta & Variabel

let name = "Swift"       // constant (immutable)
var count = 0            // variable (mutable)
count += 1
let pi: Double = 3.14   // explicit type annotation

Komentar

// single-line comment
/* multi-line
   comment */
/// documentation comment (Markdown supported)

Tipe Data

Tipe Dasar

Int	Integer berukuran platform (64-bit di sistem modern)
Double	Floating point 64-bit (lebih diutamakan dari Float)
Float	Floating point 32-bit
Bool	`true` / `false`
String	String Unicode, value type
Character	Satu extended grapheme cluster

Inferensi Tipe & Konversi

let score = 95              // inferred as Int
let gpa = 3.8              // inferred as Double
let total = Double(score) + gpa  // explicit conversion
let label = "Score: \(score)"    // string interpolation

Tuple

let point = (x: 3, y: 5)
print(point.x)            // named access
let (x, y) = point        // decompose
let (first, _) = point    // ignore second value

Type Alias

typealias Coordinate = (Double, Double)
let origin: Coordinate = (0.0, 0.0)

Alur Kontrol

If / Else

if score > 90 { print("A") }
else if score > 80 { print("B") }
else { print("C") }

Switch

switch grade {
case "A": print("excellent")
case "B", "C": print("passing")
default: print("unknown")
}

Loop

for i in 0..<5 { }            // half-open range
for name in names { }          // collection
for (i, val) in list.enumerated() { }
while condition { }
repeat { } while condition     // do-while

Guard

func process(value: Int?) {
    guard let v = value, v > 0 else { return }
    print(v)   // v is unwrapped and in scope
}

Fungsi

Fungsi Dasar

func greet(name: String) -> String {
    return "Hello, \(name)!"
}
greet(name: "Alice")

Label Argumen

func move(from start: Int, to end: Int) -> Int {
    return end - start
}
move(from: 0, to: 10)  // external labels
func add(_ a: Int, _ b: Int) -> Int { a + b }

Parameter Default & Variadic

func join(_ items: String..., separator: String = ", ") -> String {
    items.joined(separator: separator)
}
join("a", "b", "c")

Parameter inout

func double(_ x: inout Int) { x *= 2 }
var num = 5
double(&num)   // num is now 10

Closure

Sintaks Closure

let double = { (x: Int) -> Int in return x * 2 }
let nums = [3, 1, 2]
let sorted = nums.sorted { $0 < $1 }
let mapped = nums.map { $0 * 10 }

Trailing Closure

UIView.animate(withDuration: 0.3) {
    view.alpha = 0.0
}

Menangkap Nilai

func makeCounter() -> () -> Int {
    var count = 0
    return { count += 1; return count }
}
let counter = makeCounter()  // counter() => 1, 2, ...

Class & Struct

Struct (Value Type)

struct Point {
    var x: Double
    var y: Double
}
var p = Point(x: 1, y: 2)  // auto memberwise init

Class (Reference Type)

class Vehicle {
    var speed: Double = 0
    init(speed: Double) { self.speed = speed }
}
class Car: Vehicle { var gear: Int = 1 }

Struct vs Class

struct	Value type, disalin saat penugasan, tanpa inheritance
class	Reference type, dibagikan via referensi, mendukung inheritance
mutating	Keyword wajib untuk metode struct yang memodifikasi `self`
deinit	Deinitializer khusus class (dipanggil sebelum dealokasi)

Protocol

Definisi & Konformitas

protocol Drawable {
    var description: String { get }
    func draw()
}
struct Circle: Drawable { /* implement required members */ }

Protocol Extension

extension Drawable {
    func log() { print("Drawing: \(description)") }
}
// all Drawable conformers get log() for free

Protocol Umum

Equatable	Perbandingan `==` dan `!=`
Comparable	Pengurutan `<`, `>`, `<=`, `>=`
Hashable	Dapat digunakan sebagai kunci Dictionary atau dalam Set
Codable	Encodable + Decodable (JSON, Plist)
CustomStringConvertible	Properti `description` kustom
Identifiable	Membutuhkan properti `id` (SwiftUI)

Optional

Deklarasi Optional

var name: String? = "Alice"  // may contain String or nil
var age: Int? = nil          // currently nil
let count: Int = 5           // non-optional, never nil

Unwrapping

if let n = name { print(n) }       // optional binding
guard let n = name else { return }  // guard
let n = name ?? "Unknown"           // nil coalescing
let n = name!                       // force unwrap (crashes if nil)

Optional Chaining

let count = user?.address?.zip?.count
// returns nil if any link in the chain is nil
user?.save()   // called only if user is non-nil

Optional Map

let length = name.map { $0.count }   // Int?
let upper = name.flatMap { $0.isEmpty ? nil : $0.uppercased() }

Enum

Enum Dasar

enum Direction {
    case north, south, east, west
}
var heading = Direction.north
heading = .east   // type inferred

Associated Values

enum Result {
    case success(data: String)
    case failure(code: Int, message: String)
}
if case .failure(let code, _) = r { print(code) }

Raw Values

enum Planet: Int {
    case mercury = 1, venus, earth, mars
}
let p = Planet(rawValue: 3)   // Optional(.earth)
print(Planet.earth.rawValue)  // 3

Metode pada Enum

enum Suit: String, CaseIterable {
    case hearts, diamonds, clubs, spades
}
Suit.allCases.forEach { print($0.rawValue) }

Penanganan Error

Mendefinisikan Error

enum NetworkError: Error {
    case badURL
    case timeout(seconds: Int)
    case serverError(code: Int)
}

Melempar & Menangkap

func fetch(url: String) throws -> Data {
    guard url.hasPrefix("https") else { throw NetworkError.badURL }
    return Data()
}
do { let data = try fetch(url: "https://example.com") }
catch { print("Error: \(error)") }

Varian try

try	Harus dalam `do-catch`, meneruskan error
try?	Mengembalikan optional, `nil` jika error
try!	Force try, crash jika error
throws	Fungsi dapat melempar error
rethrows	Melempar hanya jika argumen closure melempar

REFERENSI CEPAT SWIFT