Swift — Data Types

Basic types

Type	Description
Bool	true or false
Int	64-bit signed integer
UInt	64-bit unsigned integer
Float	32-bit float
Double	64-bit float
String	UTF-8 text
Character	Single Unicode character

Numeric types

let i: Int = 42
let d: Double = 3.14159
let f: Float = 3.14
let u: UInt = 42

print(i, d, f, u)

Strings

let s = "Hello, World!"
let multiline = """
    This is a
    multiline string
    """
let interpolated = "Length: \(s.count)"

Arrays

let nums = [1, 2, 3, 4, 5]
var mutable = [1, 2, 3]
mutable.append(4)
mutable.remove(at: 0)
print(mutable) // [2, 3, 4]

Dictionaries

let ages = ["Alice": 30, "Bob": 25]
print(ages["Alice"] ?? 0)

var mutable = [String: Int]()
mutable["Charlie"] = 35

Sets

let set: Set = [1, 2, 3, 2, 1]
print(set) // {1, 2, 3}
print(set.contains(2)) // true

Tuples

let point = (x: 3.0, y: 4.0)
print(point.x, point.y)

let (x, y) = point
print(x, y)

Structs

struct Point {
    var x: Double
    var y: Double

    func distance(to other: Point) -> Double {
        let dx = x - other.x
        let dy = y - other.y
        return sqrt(dx * dx + dy * dy)
    }
}

let p1 = Point(x: 0, y: 0)
let p2 = Point(x: 3, y: 4)
print(p1.distance(to: p2)) // 5.0

Enums

enum Direction {
    case north, south, east, west
}

enum HttpStatus: Int {
    case ok = 200
    case notFound = 404
    case serverError = 500
}

let dir = Direction.north
let code = HttpStatus.notFound
print(code.rawValue) // 404

Mini Practice

Write Swift code that:

1. Creates arrays and dictionaries
2. Defines a struct with a method
3. Creates an enum with raw values
4. Demonstrates tuple destructuring

Up Next

In the next lesson, you'll learn about Type Inference — Swift's type system.