# beginInterval(_:id:) Begins a signposted interval. ``` func beginInterval(_ name: StaticString, id: OSSignpostID = .exclusive) -> OSSignpostIntervalState ``` ## Parameters `name` The signpost’s name. `id` The signpost’s identifier. The default value is [`exclusive`](/documentation/os/OSSignpostID/exclusive). ## Return Value The interval state that the signposter derives from the specified `id` parameter. ## Discussion The signposter uses a signpost ID to pair the beginning and the end of a signposted interval, which is necessary because multiple intervals with the same configuration and scope can be in-flight simultaneously. If only one interval with a specific configuration can execute at any particular time, use [`exclusive`](/documentation/os/OSSignpostID/exclusive) for the `id` parameter. Otherwise, use the [`makeSignpostID()`](/documentation/os/OSSignposter/makeSignpostID()) and [`makeSignpostID(from:)`](/documentation/os/OSSignposter/makeSignpostID(from:)) methods to generate a signpost identifier. To end a signposted interval, pass the return value to one of the [`endInterval(_:_:)`](/documentation/os/OSSignposter/endInterval(_:_:)) or [`endInterval(_:_:_:)`](/documentation/os/OSSignposter/endInterval(_:_:_:)) methods. If you don’t have access to the returned interval state when you want to end the signposted interval, recreate it by passing the same signpost ID to the [`beginState(id:)`](/documentation/os/OSSignpostIntervalState/beginState(id:)) method. If you need to pass the returned interval state across process boundaries, you must encode it first. For more information, see [`OSSignpostIntervalState`](/documentation/os/OSSignpostIntervalState). The following example demonstrates how to use a signpost ID and interval state to signpost the beginning and the end of an interval: ```swift // Create a signposter that uses the default subsystem. let signposter = OSSignposter() // Generate a signpost ID to associate with the signposted interval. let signpostID = signposter.makeSignpostID() // Create a name that the signposter uses, along with the // signpost ID, to disambiguate the begin call and end call. // The type must be StaticString. let name: StaticString = "Example Signpost" // Begin a signposted interval and keep a reference to the // returned interval state. let state = signposter.beginInterval(name, id: signpostID) // Perform one or more tasks that you want to measure. // Use the interval state from the begin call to end the // corresponding signposted interval. signposter.endInterval(name, state) ``` --- 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)