# Optional.Publisher The type of a Combine publisher that publishes the value of a Swift optional instance to each subscriber exactly once, if the instance has any value at all. ``` struct Publisher ``` ## Overview In contrast with the publisher, which always produces a single value, this publisher might not send any values and instead finish normally, if [`output`](/documentation/Swift/Optional/Publisher-swift.struct/output-swift.property) is `nil`. ## Topics ### Declaring Publisher Topography [`typealias Output`](/documentation/Swift/Optional/Publisher-swift.struct/Output-swift.typealias) The kind of value published by this publisher. [`typealias Failure`](/documentation/Swift/Optional/Publisher-swift.struct/Failure) The kind of error this publisher might publish. ### Creating an Optional Publisher [`init(Optional.Publisher.Output?)`](/documentation/Swift/Optional/Publisher-swift.struct/init(_:)) Creates a publisher to emit the value of the optional, or to finish immediately if the optional doesn’t have a value. ### Inpsecting Publisher Properties [`let output: Optional.Publisher.Output?`](/documentation/Swift/Optional/Publisher-swift.struct/output-swift.property) The output to deliver to each subscriber. ### Working with Subscribers [`func receive(subscriber: S)`](/documentation/Swift/Optional/Publisher-swift.struct/receive(subscriber:)) Implements the Publisher protocol by accepting the subscriber and immediately publishing the optional’s value if it has one, or finishing normally if it doesn’t. ### Instance Methods [`func allSatisfy((Optional.Publisher.Output) -> Bool) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/allSatisfy(_:)) [`func collect() -> Optional<[Optional.Publisher.Output]>.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/collect()) [`func compactMap((Optional.Publisher.Output) -> T?) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/compactMap(_:)) [`func contains(Optional.Publisher.Output) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/contains(_:)) [`func contains(where: (Optional.Publisher.Output) -> Bool) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/contains(where:)) [`func count() -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/count()) [`func drop(while: (Optional.Publisher.Output) -> Bool) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/drop(while:)) [`func dropFirst(Int) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/dropFirst(_:)) [`func filter((Optional.Publisher.Output) -> Bool) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/filter(_:)) [`func first() -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/first()) [`func first(where: (Optional.Publisher.Output) -> Bool) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/first(where:)) [`func ignoreOutput() -> Empty.Publisher.Output, Optional.Publisher.Failure>`](/documentation/Swift/Optional/Publisher-swift.struct/ignoreOutput()) [`func last() -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/last()) [`func last(where: (Optional.Publisher.Output) -> Bool) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/last(where:)) [`func map((Optional.Publisher.Output) -> T) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/map(_:)) [`func max() -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/max()) [`func max(by: (Optional.Publisher.Output, Optional.Publisher.Output) -> Bool) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/max(by:)) [`func min() -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/min()) [`func min(by: (Optional.Publisher.Output, Optional.Publisher.Output) -> Bool) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/min(by:)) [`func output(at: Int) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/output(at:)) [`func output(in: R) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/output(in:)) [`func prefix(Int) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/prefix(_:)) [`func prefix(while: (Optional.Publisher.Output) -> Bool) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/prefix(while:)) [`func reduce(T, (T, Optional.Publisher.Output) -> T) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/reduce(_:_:)) [`func removeDuplicates() -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/removeDuplicates()) [`func removeDuplicates(by: (Optional.Publisher.Output, Optional.Publisher.Output) -> Bool) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/removeDuplicates(by:)) [`func replaceEmpty(with: Optional.Publisher.Output) -> Just`](/documentation/Swift/Optional/Publisher-swift.struct/replaceEmpty(with:)) [`func replaceError(with: Optional.Publisher.Output) -> Optional.Publisher.Output>.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/replaceError(with:)) [`func retry(Int) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/retry(_:)) [`func scan(T, (T, Optional.Publisher.Output) -> T) -> Optional.Publisher`](/documentation/Swift/Optional/Publisher-swift.struct/scan(_:_:)) ## Relationships ### Conforms To [`Publisher`](/documentation/Combine/Publisher) [`Equatable`](/documentation/Swift/Equatable) --- 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)