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
}

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)

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

Transforming a Boolean

static func !(Bool)

Performs a logical NOT operation on a Boolean value.

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

Performs a logical OR operation on two Boolean values.

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

Performs a logical AND operation on two Boolean values.

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 hashValue: Int

The hash value for the Boolean value.

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

Infrequently Used Intializers

init()

Creates an instance initialized to false.

init(booleanLiteral: Bool)

Creates an instance initialized to the specified Boolean literal.