Strings and Characters

Strings are collections of characters. Strings have the type String, and characters have the type Character. Strings can be used to work with text in a Unicode-compliant way. Strings are immutable.

String and character literals are enclosed in double quotation marks (").

let someString = "Hello, world!"

String literals may contain escape sequences. An escape sequence starts with a backslash (\):

• \0: Null character

• \\: Backslash

• \t: Horizontal tab

• \n: Line feed

• \r: Carriage return

• \": Double quotation mark

• \': Single quotation mark

• \u: A Unicode scalar value, written as \u{x},

  where x is a 1–8 digit hexadecimal number

  which needs to be a valid Unicode scalar value,

  i.e., in the range 0 to 0xD7FF and 0xE000 to 0x10FFFF inclusive

// Declare a constant which contains two lines of text
// (separated by the line feed character `\n`), and ends
// with a thumbs up emoji, which has code point U+1F44D (0x1F44D).
//
let thumbsUpText =
    "This is the first line.\nThis is the second line with an emoji: \u{1F44D}"

The type Character represents a single, human-readable character. Characters are extended grapheme clusters, which consist of one or more Unicode scalars.

For example, the single character ü can be represented in several ways in Unicode. First, it can be represented by a single Unicode scalar value ü ("LATIN SMALL LETTER U WITH DIAERESIS", code point U+00FC). Second, the same single character can be represented by two Unicode scalar values: u ("LATIN SMALL LETTER U", code point U+0075), and "COMBINING DIAERESIS" (code point U+0308). The combining Unicode scalar value is applied to the scalar before it, which turns a u into a ü.

Still, both variants represent the same human-readable character ü.

let singleScalar: Character = "\u{FC}"
// `singleScalar` is `ü`
let twoScalars: Character = "\u{75}\u{308}"
// `twoScalars` is `ü`

Another example where multiple Unicode scalar values are rendered as a single, human-readable character is a flag emoji. These emojis consist of two "REGIONAL INDICATOR SYMBOL LETTER" Unicode scalar values.

// Declare a constant for a string with a single character, the emoji
// for the Canadian flag, which consists of two Unicode scalar values:
// - REGIONAL INDICATOR SYMBOL LETTER C (U+1F1E8)
// - REGIONAL INDICATOR SYMBOL LETTER A (U+1F1E6)
//
let canadianFlag: Character = "\u{1F1E8}\u{1F1E6}"
// `canadianFlag` is `🇨🇦`