Bool

A value type whose instances are either true or false.

@frozen struct Bool

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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.

Citizens in Swift

Conformances

protocol CVarArg
A type whose instances can be encoded, and appropriately passed, as elements of a C va_list.
protocol CustomReflectable
A type that explicitly supplies its own mirror.
protocol CustomStringConvertible
A type with a customized textual representation.
protocol Decodable
A type that can decode itself from an external representation.
protocol Encodable
A type that can encode itself to an external representation.
protocol Equatable
A type that can be compared for value equality.
protocol ExpressibleByBooleanLiteral
A type that can be initialized with the Boolean literals true and false.
protocol Hashable
A type that can be hashed into a Hasher to produce an integer hash value.
protocol LosslessStringConvertible
A type that can be represented as a string in a lossless, unambiguous way.
protocol Sendable
A type whose values can safely be passed across concurrency domains by copying.

Type members

init()
Creates an instance initialized to false.
init(Bool)
Creates an instance equal to the given Boolean value.
init?(String)
Creates a new Boolean value from the given string.
init(booleanLiteral: Bool)
Creates an instance initialized to the specified Boolean literal.
init(from: any Decoder) throws
Creates a new instance by decoding from the given decoder.
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.
static func ! (a: Bool) -> Bool
Performs a logical NOT operation on a Boolean value.
static func && (lhs: Bool, rhs: @autoclosure () throws -> Bool) rethrows -> Bool
Performs a logical AND operation on two Boolean values.
static func == (lhs: Bool, rhs: Bool) -> Bool
static func || (lhs: Bool, rhs: @autoclosure () throws -> Bool) rethrows -> Bool
Performs a logical OR operation on two Boolean values.

Instance members

var customMirror: Mirror
A mirror that reflects the Bool instance.
var description: String
A textual representation of the Boolean value.
func encode(to: any Encoder) throws
Encodes this value into the given encoder.
func hash(into: inout Hasher)
Hashes the essential components of this value by feeding them into the given hasher.
func toggle()
Toggles the Boolean variable’s value.

Show obsolete interfaces (1)

var customPlaygroundQuickLook: _PlaygroundQuickLook
A custom playground Quick Look for the Bool instance.

Type features

static func != (lhs: Self, rhs: Self) -> Bool
Returns a Boolean value indicating whether two values are not equal.

Available in Foundation

Type members

Show obsolete interfaces (1)

init(NSNumber)

Extension in BSON

Conformances

Instance features

Extension in MultipartKit

Conformances

protocol MultipartPartConvertible
A protocol to provide custom behaviors for parsing and serializing types from and to multipart data.

Type members

init?(multipart: MultipartPart)

Instance members

var multipart: MultipartPart?

Extension in ArgumentParser

Conformances

protocol ExpressibleByArgument
A type that can be expressed as a command-line argument.

Type features

Instance features

var defaultValueDescription: String

Extension in SwiftASN1

Conformances

protocol BERImplicitlyTaggable
protocol BERParseable
Defines a type that can be parsed from a BER-encoded form, which is a superset of DER.
protocol BERSerializable
Defines a type that can be serialized in BER-encoded form.
protocol DERImplicitlyTaggable
An ASN.1 node that can tolerate having an implicit tag.
protocol DERParseable
Defines a type that can be parsed from a DER-encoded form.
protocol DERSerializable
Defines a type that can be serialized in DER-encoded form.

Type members

Instance members

func serialize(into: inout DER.Serializer, withIdentifier: ASN1Identifier) throws

Type features

init(asn1Any: ASN1Any) throws
Construct this node from an ASN.1 ANY object.
init(asn1Any: ASN1Any, withIdentifier: ASN1Identifier) throws
Construct this node from an ASN.1 ANY object.
init(berASN1Any: ASN1Any) throws
Construct this node from an ASN.1 ANY object.
init(berASN1Any: ASN1Any, withIdentifier: ASN1Identifier) throws
Construct this node from an ASN.1 ANY object.
init(berEncoded: inout ASN1NodeCollection.Iterator) throws
init(berEncoded: ASN1Node) throws
By default, uses the underlying DERParseable initializer.
init(berEncoded: [UInt8]) throws
Initialize this object from a serialized BER representation.
init(berEncoded: ArraySlice<UInt8>) throws
Initialize this object from a serialized BER representation.
init(berEncoded: ASN1Node) throws
Initialize this object from a serialized BER representation.
init(berEncoded: inout ASN1NodeCollection.Iterator, withIdentifier: ASN1Identifier) throws
Initialize this object as one element of a constructed ASN.1 object.
init(berEncoded: [UInt8], withIdentifier: ASN1Identifier) throws
Initialize this object from a serialized BER representation.
init(berEncoded: ArraySlice<UInt8>, withIdentifier: ASN1Identifier) throws
Initialize this object from a serialized BER representation.
init(derEncoded: inout ASN1NodeCollection.Iterator) throws
Initialize this object as one element of a constructed ASN.1 object.
init(derEncoded: [UInt8]) throws
Initialize this object from a serialized DER representation.
init(derEncoded: ArraySlice<UInt8>) throws
Initialize this object from a serialized DER representation.
init(derEncoded: ASN1Node) throws
init(derEncoded: inout ASN1NodeCollection.Iterator, withIdentifier: ASN1Identifier) throws
Initialize this object as one element of a constructed ASN.1 object.
init(derEncoded: [UInt8], withIdentifier: ASN1Identifier) throws
Initialize this object from a serialized DER representation.
init(derEncoded: ArraySlice<UInt8>, withIdentifier: ASN1Identifier) throws
Initialize this object from a serialized DER representation.

Instance features

func serialize(into: inout DER.Serializer) throws

Extension in Atomics

Conformances

protocol AtomicValue
A type that supports atomic operations through a separate atomic storage representation.

Types

struct AtomicRepresentation

Extension in MMIO

Conformances

protocol BitFieldProjectable

Type members

Instance members

func storage<Storage>(Storage.Type) -> Storage

typealias AtomicWrapper

protocol ExpressibleByLiteralSyntax
A Swift type whose value can be represented directly in source code by a Swift literal.

Instance members

func makeLiteralSyntax() -> BooleanLiteralExprSyntax

Extension in Vapor

Conformances

protocol AsyncRequestDecodable
Can convert Request to a Self.
protocol AsyncResponseEncodable
Can convert self to a Response.
protocol Content
Convertible to / from content in an HTTP message.
protocol RequestDecodable
Can convert Request to a Self.
protocol ResponseEncodable
Can convert self to a Response.

Type features

Instance features

func afterDecode() throws
func beforeEncode() throws
func encodeResponse(for: Request) -> EventLoopFuture<Response>
func encodeResponse(status: HTTPStatus, headers: HTTPHeaders, for: Request) -> EventLoopFuture<Response>
Asynchronously encodes Self into a Response, setting the supplied status and headers.

Extension in Yams

Conformances

protocol NodeRepresentable
Type is representable as Node.
protocol ScalarConstructible
Types conforming to this protocol can be extracted Node.Scalars.
protocol ScalarRepresentable
Type is representable as Node.scalar.
protocol YAMLEncodable
Types conforming to this protocol can be encoded by YamlEncoder.

Type members

static func construct(from: Node.Scalar) -> Bool?
Construct an instance of Bool, if possible, from the specified scalar.

Instance members

func represented() -> Node.Scalar
This value’s Node.scalar representation.

Instance features

func box() -> Node
Returns this value wrapped in a Node.scalar.