CODEWITHSUNDEEP
swift
sabi
sabi

Reputation: 423

Swift "switch case" abbreviated syntax

While reading a tutorial about a deck of card, here, I found:

enum Suit: Int, CustomStringConvertible {
  case Clubs = 1, Diamonds, Hearts, Spades

  var description: String {
    return ["♣️", "♦️", "❤️", "♠️"][rawValue - 1]
  }
}

works well in playground. I understand it should be a short syntax for:

enum Suit: Int, CustomStringConvertible {
  case Clubs = 1, Diamonds, Hearts, Spades

  var description: String {
    switch self {
      case .Spades:
        return "♠️"
      case .Clubs:
        return "♣️"
      case .Diamonds:
        return "♦️"
      case .Hearts:
        return "♥️"
    }
  }
}

I couldn't find any documentation on this syntax. Does it have a name or is it described in the official documentation or any other place? Thanks for any contribution.

Upvotes: 1

Views: 207

Answers (2)

John Estropia
John Estropia

Reputation: 17500

["♣️", "♦️", "❤️", "♠️"][rawValue - 1]

is not a special syntax. Here's how it would be broken down:

let array: [String] = ["♣️", "♦️", "❤️", "♠️"]
let index: Int = self.rawValue - 1
let symbol = array[index]
return symbol

Upvotes: 2

jtbandes
jtbandes

Reputation: 118781

This isn't any special syntax by itself. It's two separate things:

  1. An array literal, ["♣️", "♦️", "❤️", "♠️"] which is an Array<String> a.k.a. [String]

  2. Array subscripting syntax: myArray[i] or, in this case, array[rawValue - 1] where array is the literal from #1.

["♣️", "♦️", "❤️", "♠️"][rawValue - 1] just means the rawValue - 1th entry of that array. It relies on the fact that the enum is declared with enum Suit: Int so that each value has an underlying rawValue.

Upvotes: 3

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