# beginInterval(_:id:_:) Begins a signposted interval and attaches the specified message. ``` func beginInterval(_ name: StaticString, id: OSSignpostID = .exclusive, _ message: SignpostMetadata) -> OSSignpostIntervalState ``` ## Parameters `name` The signpost’s name. `id` The signpost’s identifier. The default value is [`exclusive`](/documentation/os/OSSignpostID/exclusive). `message` The interpolated string that the signposter attaches to the signpost. Each of the message’s interpolations can specify individual formatting and privacy options. For more information, see [Message Argument Formatters](/documentation/os/message-argument-formatters). ## Return Value The interval state that the signposter derives from the specified `id` parameter. ## Discussion > Important: > Don’t create an instance of ``doc://com.apple.os/documentation/os/SignpostMetadata``. Instead, provide an interpolated string as the `message` parameter and the system converts it automatically. 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 shows how to use a signpost ID and interval state to signpost the beginning and the end of an interval, and also demonstrates the use of message interpolation: ```swift let accountNumber = "12345678" // 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 = "Account Reconciliation" // Begin a signposted interval and attach a message that securely // interpolates sensitive data. let state = signposter.beginInterval(name, id: signpostID, "Account: \(accountNumber, privacy: .sensitive(mask: .hash))") // Perform the related tasks you want to measure. processTransactions() updateBalance() // 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)