ProtocolSwift5.9.0

Sendable

A type whose values can safely be passed across concurrency domains by copying.

protocol Sendable

You can safely pass values of a sendable type from one concurrency domain to another — for example, you can pass a sendable value as the argument when calling an actor’s methods. All of the following can be marked as sendable:

Value types
Reference types with no mutable storage
Reference types that internally manage access to their state
Functions and closures (by marking them with @Sendable)

Although this protocol doesn’t have any required methods or properties, it does have semantic requirements that are enforced at compile time. These requirements are listed in the sections below. Conformance to Sendable must be declared in the same file as the type’s declaration.

To declare conformance to Sendable without any compiler enforcement, write @unchecked Sendable. You are responsible for the correctness of unchecked sendable types, for example, by protecting all access to its state with a lock or a queue. Unchecked conformance to Sendable also disables enforcement of the rule that conformance must be in the same file.

For information about the language-level concurrency model that Task is part of, see Concurrency in The Swift Programming Language.

Sendable Structures and Enumerations

To satisfy the requirements of the Sendable protocol, an enumeration or structure must have only sendable members and associated values. In some cases, structures and enumerations that satisfy the requirements implicitly conform to Sendable:

Frozen structures and enumerations
Structures and enumerations that aren’t public and aren’t marked @usableFromInline.

Otherwise, you need to declare conformance to Sendable explicitly.

Structures that have nonsendable stored properties and enumerations that have nonsendable associated values can be marked as @unchecked Sendable, disabling compile-time correctness checks, after you manually verify that they satisfy the Sendable protocol’s semantic requirements.

Sendable Actors

All actor types implicitly conform to Sendable because actors ensure that all access to their mutable state is performed sequentially.

Sendable Classes

To satisfy the requirements of the Sendable protocol, a class must:

Be marked final
Contain only stored properties that are immutable and sendable
Have no superclass or have NSObject as the superclass

Classes marked with @MainActor are implicitly sendable, because the main actor coordinates all access to its state. These classes can have stored properties that are mutable and nonsendable.

Classes that don’t meet the requirements above can be marked as @unchecked Sendable, disabling compile-time correctness checks, after you manually verify that they satisfy the Sendable protocol’s semantic requirements.

Sendable Functions and Closures

Instead of conforming to the Sendable protocol, you mark sendable functions and closures with the @Sendable attribute. Any values that the function or closure captures must be sendable. In addition, sendable closures must use only by-value captures, and the captured values must be of a sendable type.

In a context that expects a sendable closure, a closure that satisfies the requirements implicitly conforms to Sendable — for example, in a call to Task.detached(priority:operation:).

You can explicitly mark a closure as sendable by writing @Sendable as part of a type annotation, or by writing @Sendable before the closure’s parameters — for example:

let sendableClosure = { @Sendable (number: Int) -> String in
    if number > 12 {
        return "More than a dozen."
    } else {
        return "Less than a dozen"
    }
}

Sendable Tuples

To satisfy the requirements of the Sendable protocol, all of the elements of the tuple must be sendable. Tuples that satisfy the requirements implicitly conform to Sendable.

Sendable Metatypes

Metatypes such as Int.Type implicitly conform to the Sendable protocol.

Citizens in Swift

Subtypes

protocol CodingKey
A type that can be used as a key for encoding and decoding.
protocol DurationProtocol
A type that defines a duration for a given InstantProtocol type.
protocol Error
A type representing an error value that can be thrown.
protocol InstantProtocol
protocol UnsafeSendable
A type whose values can safely be passed across concurrency domains by copying, but which disables some safety checking at the conformance site.

Available in _Concurrency

Subtypes

protocol Actor
Common protocol to which all actors conform.
protocol AnyActor
Common marker protocol providing a shared “base” for both (local) Actor and (potentially remote) DistributedActor types.
protocol Clock
A mechanism in which to measure time, and delay work until a given point in time.
protocol Executor
A service that can execute jobs.
protocol SerialExecutor
A service that executes jobs.

Available in Distributed

Subtypes

protocol DistributedActor
The such obtained actor system is then used to resolve(id:using:) the decoded ID.
protocol DistributedActorSystem
A distributed actor system underpins and implements all functionality of distributed actors.
protocol DistributedActorSystemError
Error protocol to which errors thrown by any DistributedActorSystem should conform.

Available in _RegexParser

Subtypes

protocol LocatedErrorProtocol

Available in Foundation

Subtypes

protocol CustomNSError
Describes an error type that specifically provides a domain, code, and user-info dictionary.
protocol LocalizedError
Describes an error that provides localized messages describing why an error occurred and provides more information about the error.
protocol RecoverableError
Describes an error that may be recoverable by presenting several potential recovery options to the user.

Extension in BSON

Subtypes

protocol Primitive

Extension in ConsoleKit

Subtypes

protocol ActivityBar
An ActivityIndicatorType that renders an activity bar on a single line.
protocol ActivityIndicatorType
ActivityIndicatorTypes are responsible for drawing / rendering the current ActivityIndicatorState to the Console.
protocol AnyAsyncCommand
A type-erased Command.
protocol AsyncCommand
A command that can be run through a Console.
protocol AsyncCommandGroup
A group of named commands that can be run through a Console.
protocol Console
Protocol for powering styled Console I/O.
protocol LoggerFragment
A fragment of a log message.
protocol TimestampSource
A protocol to allow mocking the timestamp for tests

Extension in AsyncSequenceValidation

Subtypes

Extension in X509

Subtypes

protocol OCSPRequester

Extension in TraceableErrors

Subtypes

protocol NamedError
An error type that supports printing with a custom heading.
protocol TraceableError
A link in a propogated error.

Extension in Logging

Subtypes

protocol LogHandler
A LogHandler is an implementation of a logging backend.
protocol _SwiftLogSendableLogHandler

Extension in CoreMetrics

Subtypes

protocol CounterHandler
A CounterHandler represents a backend implementation of a Counter.
protocol FloatingPointCounterHandler
A FloatingPointCounterHandler represents a backend implementation of a FloatingPointCounter.
protocol MeterHandler
A MeterHandler represents a backend implementation of a Meter.
protocol MetricsFactory
The MetricsFactory is the bridge between the MetricsSystem and the metrics backend implementation. MetricsFactory’s role is to initialize concrete implementations of the various metric types:
protocol RecorderHandler
A RecorderHandler represents a backend implementation of a Recorder.
protocol TimerHandler
A TimerHandler represents a backend implementation of a Timer.
protocol _SwiftMetricsSendableProtocol

Extension in Durations

Subtypes

protocol QuantizedDuration<RawValue>

Extension in MongoDriver

Subtypes

protocol MongoCommand<Response>
A type that represents a MongoDB command. All public command types (and command protocols) ultimately inherit from this protocol.
protocol MongoFailpoint
protocol MongoImplicitSessionCommand<Response>
A type that can encode a MongoDB command that can be run as part of a session, which can be implicitly generated if the command is sent to a deployment at large.
protocol MongoIterableCommand<Element>
protocol MongoLoggingTarget
protocol MongoRetryableError
protocol MongoTransactableCommand<Response>

Extension in NIOCore

Subtypes

protocol Channel
A Channel is easiest thought of as a network socket. But it can be anything that is capable of I/O operations such as read, write, connect, and bind.
protocol ChannelOption
A configuration option that can be set on a Channel to configure different behaviour.
protocol EventLoop
An EventLoop processes IO / tasks in an endless loop for Channels until it’s closed.
protocol EventLoopGroup
Provides an endless stream of EventLoops to use.
protocol MulticastChannel
A MulticastChannel is a Channel that supports IP multicast operations: that is, a channel that can join multicast groups.
protocol NIOAsyncSequenceProducerBackPressureStrategy
A protocol for the back-pressure strategy of the NIOAsyncSequenceProducer.
protocol NIOAsyncSequenceProducerDelegate
The delegate of NIOAsyncSequenceProducer.
protocol NIOAsyncWriterSinkDelegate
The delegate of the NIOAsyncWriter. It is the consumer of the yielded writes to the NIOAsyncWriter. Furthermore, the delegate gets informed when the NIOAsyncWriter terminated.
protocol NIOSerialEventLoopExecutor
A helper protocol that can be mixed in to a NIO EventLoop to provide an automatic conformance to SerialExecutor.
protocol RecvByteBufferAllocator
Allocates ByteBuffers to be used to read bytes from a Channel and records the number of the actual bytes that were used.
protocol SocketOptionProvider
This protocol defines an object, most commonly a Channel, that supports setting and getting socket options (via setsockopt/getsockopt or similar). It provides a strongly typed API that makes working with larger, less-common socket options easier than the ChannelOption API allows.
protocol _NIOPreconcurrencySendable

Extension in NIOExtras

Subtypes

protocol NIOExtrasError
Base type for errors from NIOExtras

Extension in NIOHPACK

Subtypes

protocol NIOHPACKError

Extension in NIOHTTP2

Subtypes

protocol NIOHTTP2Error
The base protocol for all errors thrown by NIOHTTP2.

Extension in NIOSSL

Subtypes

protocol NIOSSLCustomPrivateKey
NIOSSLCustomPrivateKey defines the interface of a custom, non-BoringSSL private key.

Extension in HTTPServer

Subtypes

protocol HTTPServerDelegate<Operation>
protocol HTTPServerOperation
A user-defined type for a server’s representation of an HTTP request.
protocol ServerAuthority

Extension in SymbolGraphParts

Subtypes

Extension in SymbolGraphLinker

Subtypes

protocol StaticLinkerError

Extension in UnidocLinker

Subtypes

protocol DynamicLinkerError

Extension in GitHubAPI

Subtypes

protocol GitHubApplication<Credentials>
The essence of a GitHub application. Not to be confused with GitHubApp.
protocol GitHubRateLimitError

Extension in UnidocDB

Subtypes

Extension in UnidocQueries

Subtypes

Extension in Vapor

Subtypes

protocol AbortError
Errors conforming to this protocol will always be displayed by Vapor to the end-user (even in production mode where most errors are silenced).
protocol AsyncAuthenticator
Helper for creating authentication middleware.
protocol AsyncBasicAuthenticator
Helper for creating authentication middleware using the Basic authorization header.
protocol AsyncBearerAuthenticator
Helper for creating authentication middleware using the Bearer authorization header.
protocol AsyncCredentialsAuthenticator
Helper for creating authentication middleware using request body contents.
protocol AsyncMiddleware
AsyncMiddleware is placed between the server and your router. It is capable of mutating both incoming requests and outgoing responses. AsyncMiddleware can choose to pass requests on to the next AsyncMiddleware in a chain, or they can short circuit and return a custom Response if desired.
protocol AsyncRequestAuthenticator
Help for creating authentication middleware based on Request.
protocol AsyncResponder
protocol AsyncSessionAuthenticator
Helper for creating authentication middleware in conjunction with SessionsMiddleware.
protocol AsyncSessionDriver
Capable of managing CRUD operations for Sessions.
protocol Authenticatable
Capable of being authenticated.
protocol Authenticator
Helper for creating authentication middleware.
protocol BasicAuthenticator
Helper for creating authentication middleware using the Basic authorization header.
protocol BearerAuthenticator
Helper for creating authentication middleware using the Bearer authorization header.
protocol BodyStreamWriter
protocol Client
protocol CredentialsAuthenticator
Helper for creating authentication middleware using request body contents.
protocol DebuggableError
Debuggable provides an interface that allows a type to be more easily debugged in the case of an error.
protocol LifecycleHandler
protocol Middleware
Middleware is placed between the server and your router. It is capable of mutating both incoming requests and outgoing responses. Middleware can choose to pass requests on to the next Middleware in a chain, or they can short circuit and return a custom Response if desired.
protocol PasswordHasher
protocol RequestAuthenticator
Help for creating authentication middleware based on Request.
protocol Responder
protocol SessionAuthenticatable
Models conforming to this protocol can have their authentication status cached using SessionAuthenticator.
protocol SessionAuthenticator
Helper for creating authentication middleware in conjunction with SessionsMiddleware.
protocol SessionDriver
Capable of managing CRUD operations for Sessions.
protocol ValidatorResult