# init(_:as:) Creates a regular expression from the given string, using the specified capture type. ``` init(_ pattern: String, as outputType: Output.Type = Output.self) throws ``` ## Parameters `pattern` A string with regular expression syntax. `outputType` The desired type for the output captures. ## Discussion You can use this initializer to create a `Regex` instance from a regular expression that you have stored in `pattern` when you know the capture structure of the regular expression in advance. In this example, the regular expression includes two parenthesized capture groups, so the capture type is `(Substring, Substring, Substring)`. The first substring in the tuple represents the entire match, while the second and third substrings represent the first and second capture group, respectively. ``` let keyAndValue = try Regex("(.+): (.+)", as: (Substring, Substring, Substring).self) ``` This initializer throws an error if `pattern` uses invalid regular expression syntax, or if `outputType` does not match the capture structure declared by `pattern`. If you don’t know the capture structure in advance, use the `init(_:)` initializer instead. --- 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)