# init(_:) Creates a regular expression from the given string, using a dynamic capture list. ``` init(_ pattern: String) throws ``` ## Parameters `pattern` A string with regular expression syntax. ## Discussion Use this initializer to create a `Regex` instance from a regular expression that you have stored in `pattern`. ``` let simpleDigits = try Regex("[0-9]+") ``` This initializer throws an error if `pattern` uses invalid regular expression syntax. The output type of the new `Regex` is the dynamic [`AnyRegexOutput`](/documentation/Swift/AnyRegexOutput). If you know the capture structure of `pattern` ahead of time, use the `init(_:as:)` 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)