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Strings are a data type that represent a text value. Strings in Swift are a collection of Characters, which themselves hold a Unicode scalar value.

You can create a String through a string literal, which is a series of characters enclosed in double quotation marks ("). For multi-line strings, you can use triple quotation marks (""").

let hello : String = "Hello, World!"

let poem : String = """
Roses are red,
Violets are blue.
Sugar is sweet,
And so are you.
"""

Strings in Swift also obtain all of the functionality of the NSString class which was originally used in Apple's Objective-C libraries.

Character

Character is a data type that stores a single Unicode scalar value that is made up of one or more Unicode code points. A Unicode scalar value is any Unicode code point in the range U+0000 to U+D7FF inclusive or U+E000 to U+10FFFF inclusive.

let aChar : Character = "A"

Type inference

Swift can infer the type of a string literal, and will by default infer it to be a String. You can explicitly declare a string to be a Character by using the Character type annotation, which requires the value to be a single character.

let aString = "A"
let aChar: Character = "A"
print(type(of: aString)) // Prints String
print(type(of: aChar))   // Prints Character

// The following code will not compile
let badChar: Character = "Too many characters"
// Error: Cannot convert value of type 'String' to specified type 'Character'

Concatenation

In Swift, strings can be concatenated using the + operator. Characters can not be concatenated with strings using the + operator without first converting the character to a string.

print("honey" + "comb")
// Prints "honeycomb"

The append(_:) method mutates the string by adding either a string or a character to the end of it.

var greeting = "Hello"
let world = ", world"
let period: Character = "."

greeting.append(world)
print(greeting) // Prints "Hello, world"

greeting.append(period)
print(greeting) // Prints "Hello, world."

String interpolation

String interpolation is a way of constructing a String based on values from different sources like variables and expressions. To insert a value into a string using string interpolation, you place an expression or value in parentheses which are preceded by a backslash character.

let radius = 5.0
let circle = "The area of a circle with radius \(radius) is \(Double.pi * radius * radius)"
print(circle) // Prints "The area of a circle with radius 5.0 is 78.53981633974483"

String and Character properties

Strings and characters have a few different properties which can be queried to get information about the string or character.

String properties

Here are some of the most common string properties, but to find all, see the documentation.

Character properties

Here are some of the most common character properties, but to find all, see the documentation.

Type conversion

To convert a type to a string, you can use the String() initializer, which accepts a variety of types, including Int, Double, Character, and more.

let charX: Character = "x"
print(String(charX))     // Prints "x"
print(String(110))       // Prints "110"
print(String(Double.pi)) // Prints "3.141592653589793"

Special characters

Swift has a few special characters that can be used in strings.

let quote : String = "\"Hello\", he said."
print(quote) // Prints "Hello", he said.

let unicode : Character = "\u{1F496}"
print(unicode) // Prints 💖