Some Swift code examples

examples.swift

// A constant Int
let meaningOfLife = 42  

// A variable String
var greeting = "Hello!"

// Type inference on enum members
var directionToHead = CompassPoint.west
directionToHead = .east

var maybeString: String?
var maybeAnotherString: String?

maybeString = "hej"

// Optional binding
if let aString = maybeString {
    print("This is a string: \(aString)")
}

// Optional chaining
let count: Int? = maybeAnotherString?.characters.count


let point = (9, 0)
switch point {
case (let distance, 0), (0, let distance):
    print("On an axis, \(distance) from the origin")
default:
    print("Not on an axis")
}


enum Flavor {
    .vanilla
    .chocolate
    .strawberry
}

enum ASCIIControlCharacter: Character {
    case tab = "\t"
    case lineFeed = "\n"
    case carriageReturn = "\r"
}

// Sum type
enum Result<T> {
    .error(Error)
    .result(T)
}

let result = Result.success("👍")

// Recursive
enum ArithmeticExpression {
    case number(Int)
    indirect case addition(ArithmeticExpression, ArithmeticExpression)
    indirect case multiplication(ArithmeticExpression, ArithmeticExpression)
}

// Obj-C style
asyncFunction() {
    value, error in
    if error == nil {
        assert(value == nil)
        // Handle error
        return
    }
    assert(value != nil)
    // Do something with value
}

asyncFunction() {
    result in
    switch result {
    case let .error(error):
        // Handle errors
    case let .success(value):
        // Do something with value
    }
}

// Protocols
protocol YamlSerializable {
    func toYaml() -> String   
}

extension Date: YamlSerializable {
    func toYaml() -> String {
        return ISO8601DateFormatter().string(from: self)
    }
}


["foo", "", "bar"].filter(.isEmpty)

extension Collection where Iterator.Element: YamlSerializable {
    var textualDescription: String {
        let itemsAsText = self.map { $0.textualDescription }
        return "[" + itemsAsText.joined(separator: ", ") + "]"
    }
}

func foo() {
    var foobar = [[1, 2], [3, 4], [5]]
    var bar = foobar[0]
    bar[0] = [10]
    return foobar
}