# appendInterpolation(_:format:align:privacy:attributes:) Appends an interpolated numeric type using the specified attributes. ``` mutating func appendInterpolation(_ number: @autoclosure @escaping () -> T, format: OSLogIntegerFormatting = .decimal, align: OSLogStringAlignment = .none, privacy: OSLogPrivacy = .auto, attributes: String) where T : FixedWidthInteger ``` ## Parameters `number` The interpolated numeric type, which the system automatically wraps in a closure. The type itself doesn’t appear in the log message. Instead, the system incorporates the type’s integer value. `format` The format to apply to the value when the system renders it in a log message. For more information, see [`OSLogIntegerFormatting`](/documentation/os/OSLogIntegerFormatting). The default value is [`decimal`](/documentation/os/OSLogIntegerFormatting/decimal). `align` The alignment and minimum number of columns to use when the system renders the value in a log message. For more information, see [`OSLogStringAlignment`](/documentation/os/OSLogStringAlignment). The default value is [`none`](/documentation/os/OSLogStringAlignment/none). `privacy` The privacy level of the value, which the system applies when it renders the value in a log message. For more information, see [`OSLogPrivacy`](/documentation/os/OSLogPrivacy). The default value is [`auto`](/documentation/os/OSLogPrivacy/auto). `attributes` Additional information about the value. Tools that process log messages interpret these attributes, which you typically provide as key-value pairs. For example, Instruments processes any e_ngineering types_ you embed in this value. For more information, see [Instruments Developer Help](https://help.apple.com/instruments/developer/mac/current/#/devcd5016d31). ## Discussion > Important: > You don’t call this method directly. Instead, the framework calls it automatically when you append an interpolated type that adopts the protocol to a log message. --- 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)