# Publishers.Buffer A publisher that buffers elements from an upstream publisher. ``` struct Buffer where Upstream : Publisher ``` ## Topics ### Creating a buffer publisher [`init(upstream: Upstream, size: Int, prefetch: Publishers.PrefetchStrategy, whenFull: Publishers.BufferingStrategy.Failure>)`](/documentation/Combine/Publishers/Buffer/init(upstream:size:prefetch:whenFull:)) Creates a publisher that buffers elements received from an upstream publisher. ### Declaring supporting types [`typealias Output`](/documentation/Combine/Publishers/Buffer/Output) The kind of values published by this publisher. [`typealias Failure`](/documentation/Combine/Publishers/Buffer/Failure) The kind of errors this publisher might publish. ### Inspecting publisher properties [`let upstream: Upstream`](/documentation/Combine/Publishers/Buffer/upstream) The publisher from which this publisher receives elements. [`let size: Int`](/documentation/Combine/Publishers/Buffer/size) The maximum number of elements to store. [`let prefetch: Publishers.PrefetchStrategy`](/documentation/Combine/Publishers/Buffer/prefetch) The strategy for initially populating the buffer. [`let whenFull: Publishers.BufferingStrategy.Failure>`](/documentation/Combine/Publishers/Buffer/whenFull) The action to take when the buffer becomes full. ## Relationships ### Conforms To [`Publisher`](/documentation/Combine/Publisher) --- 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)