# DistributedTargetInvocationDecoder Decoder that must be provided to `executeDistributedTarget` and is used by the Swift runtime to decode arguments of the invocation. ``` protocol DistributedTargetInvocationDecoder ``` ## Overview ### Decoding DistributedActor arguments using Codable When using an actor system where `ActorID` is `Codable`, every distributed actor using that system is also implicitly `Codable` (see [`DistributedActorSystem`](/documentation/Distributed/DistributedActorSystem)). Such distributed actors are encoded as their `ActorID` stored in an `Encoder.singlevaluecontainer()`. When `Codable` is being used by such a system, the [`decodeNextArgument()`](/documentation/Distributed/DistributedTargetInvocationDecoder/decodeNextArgument()) method will be using `Decoder` to decode the incoming values, which may themselves be distributed actors. An actor system must be provided to the `Decoder` in order for a distributed actor’s `Decodable.init(from:)` to be able to return the instance of the actor. Specifically, the decoded `ActorID` is passed to the actor system’s `resolve(id:as:)` method in order to return either a local instance identified by this ID, or creating a remote actor reference. Thus, you must set the actor system the decoding is performed for, on the decoder’s `userInfo`, as follows: ``` mutating func decodeNextArgument() throws -> Argument { let argumentData: Data = /// ... // ... decoder.userInfo[.actorSystemKey] = self.actorSystem return try Argument.decode( } ``` ## Topics ### Associated Types [`associatedtype SerializationRequirement`](/documentation/Distributed/DistributedTargetInvocationDecoder/SerializationRequirement) The serialization requirement that the types passed to `decodeNextArgument` are required to conform to. The type returned by `decodeReturnType` is also expected to conform to this associated type requirement. ### Instance Methods [`func decodeErrorType() throws -> (any Any.Type)?`](/documentation/Distributed/DistributedTargetInvocationDecoder/decodeErrorType()) Decode the specific error type that the distributed invocation target has recorded. Currently this effectively can only ever be `Error.self`. [`func decodeGenericSubstitutions() throws -> [any Any.Type]`](/documentation/Distributed/DistributedTargetInvocationDecoder/decodeGenericSubstitutions()) Decode all generic substitutions that were recorded for this invocation. [`func decodeNextArgument() throws -> Argument`](/documentation/Distributed/DistributedTargetInvocationDecoder/decodeNextArgument()) Attempt to decode the next argument from the underlying buffers into pre-allocated storage pointed at by ‘pointer’. [`func decodeReturnType() throws -> (any Any.Type)?`](/documentation/Distributed/DistributedTargetInvocationDecoder/decodeReturnType()) Attempt to decode the known return type of the distributed invocation. ## Relationships ### Conforming Types [`LocalTestingInvocationDecoder`](/documentation/Distributed/LocalTestingInvocationDecoder) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)