Bool

A value type whose instances are either true or false.

Declaration

@frozen struct Bool

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: Cannot convert value of type 'Int' to expected condition type '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

Transforming a Boolean

Creating a Random Value

Describing a Boolean

description

Inspecting a Boolean

Creating a Boolean From Another Value

Converting an NSNumber to a Boolean

Encoding and Decoding

Infrequently Used Intializers

Boolean Literals

Structures

Bool.IntentDisplayName

Type Aliases

Type Properties

defaultResolverSpecification