Structure

Bool

A value type whose instances are either true or false.

Overview

Bool represents Boolean values in Swift. Create instances of Bool by using one of the Boolean literals true or false, or by assigning the result of a Boolean method or operation to a variable or constant.

var godotHasArrived = false

let numbers = 1...5
let containsTen = numbers.contains(10)
print(containsTen)
// Prints "false"

let (a, b) = (100, 101)
let aFirst = a < b
print(aFirst)
// Prints "true"

Swift uses only simple Boolean values in conditional contexts to help avoid accidental programming errors and to help maintain the clarity of each control statement. Unlike in other programming languages, in Swift, integers and strings cannot be used where a Boolean value is required.

For example, the following code sample does not compile, because it attempts to use the integer i in a logical context:

var i = 5
while i {
    print(i)
    i -= 1
}
// error: 'Int' is not convertible to 'Bool'

The correct approach in Swift is to compare the i value with zero in the while statement.

while i != 0 {
    print(i)
    i -= 1
}

Using Imported Boolean values

The C bool and Boolean types and the Objective-C BOOL type are all bridged into Swift as Bool. The single Bool type in Swift guarantees that functions, methods, and properties imported from C and Objective-C have a consistent type interface.

Topics

Comparing Boolean Values

static func != (Bool, Bool) -> Bool

Returns a Boolean value indicating whether two values are not equal.

Transforming a Boolean

func toggle()

Toggles the Boolean variable’s value.

static func ! (Bool) -> Bool

Performs a logical NOT operation on a Boolean value.

static func || (Bool, () -> Bool) -> Bool

Performs a logical OR operation on two Boolean values.

static func && (Bool, () -> Bool) -> Bool

Performs a logical AND operation on two Boolean values.

Creating a Random Value

static func random() -> Bool

Returns a random Boolean value.

static func random<T>(using: inout T) -> Bool

Returns a random Boolean value, using the given generator as a source for randomness.

Describing a Boolean

var description: String

A textual representation of the Boolean value.

Inspecting a Boolean

var customMirror: Mirror

A mirror that reflects the Bool instance.

var customPlaygroundQuickLook: PlaygroundQuickLook

A custom playground Quick Look for the Bool instance.

Deprecated
func hash(into: inout Hasher)

Hashes the essential components of this value by feeding them into the given hasher.

Creating a Boolean From Another Value

init(Bool)

Creates an instance equal to the given Boolean value.

init?(String)

Creates a new Boolean value from the given string.

init(NSNumber)Deprecated

Encoding and Decoding

init(from: Decoder)

Creates a new instance by decoding from the given decoder.

func encode(to: Encoder)

Encodes this value into the given encoder.

Infrequently Used Intializers

init()

Creates an instance initialized to false.

init(booleanLiteral: Bool)

Creates an instance initialized to the specified Boolean literal.