# appendInterpolation(_:) Interpolates the given value’s textual representation into the string literal being created. ``` mutating func appendInterpolation(_ value: T) where T : CustomStringConvertible ``` ## Discussion You don’t need to call this method directly. It’s used by the compiler when interpreting string interpolations. Instead, use string interpolation to create a new string by including values, literals, variables, or expressions enclosed in parentheses, prefixed by a backslash (`\(`…`)`). ``` let price = 2 let number = 3 let message = """ If one cookie costs \(price) dollars, \ \(number) cookies cost \(price * number) dollars. """ print(message) // Prints "If one cookie costs 2 dollars, 3 cookies cost 6 dollars." ``` --- 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)