swift-4.swift

import Foundation

struct Person: Codable {
  public let name: String
}

let person = Person(name: "Bas")
let payload = try JSONEncoder().encode(person)
let string = String(data: payload, encoding: .utf8) // {"name":"Bas"}
let decodedPerson = try JSONDecoder().decode(Person.self, from: payload) // Person(name: "Bas")

let world = "hello, world".count // 12
let family = "👨‍👩‍👧‍👦".count // 1
let multiline = """
{
  "hello": "world",
  "multiple": [
    "one": 1,
    "two": 2
  ]
}
"""

let source = "hello, world"
var frequencies: [Character: Int] = [:]
source.map { frequencies[$0, default: 0] += 1 }
frequencies // ["w": 1, "r": 1, "e": 1, "o": 2, "l": 3, ",": 1, " ": 1, "h": 1, "d": 1]

let x = frequencies["a", default: 0] // Does not store `0` at `a`;
let y = frequencies["a"] ?? 0 // these lines are equivalent

let numbers = ["one": 1, "two": 2, "three": 3, "four": 4]
let strings = numbers.mapValues(String.init) // ["three": "3", "four": "4", "one": "1", "two": "2"]
let evens = numbers.filter { $0.value % 2 == 0 } // ["four": 4, "two": 2]

struct Song {
  let artist: String
  let name: String
  private var _description: String {
    return "\(artist) - \(name)"
  }
}

extension Song: CustomStringConvertible {
  var description: String {
    return _description
  }
}

Song(artist: "Rick Astley", name: "Never Gonna Give You Up") // OK!

var collection = ["a", "b"]
collection.swapAt(0, 1) // ["b", "a"]

protocol P {}
struct S: P {}
class C: P {}
let u: AnyObject & P = C() // Compiles successfully