---
title: "prefixMatch(in:)"
framework: swift
role: symbol
role_heading: Instance Method
path: "swift/regex/prefixmatch(in:)-5oh8i"
---

# prefixMatch(in:)

Returns a match if this regex matches the given string at its start.

## Declaration

```swift
func prefixMatch(in string: String) throws -> Regex<Output>.Match?
```

## Parameters

- `string`: The string to match this regular expression against.

## Return Value

Return Value The match, if this regex matches at the start of string; otherwise, nil.

## Discussion

Discussion Call this method if you want the regular expression to succeed only when it matches only at the start of the given string. This example uses prefixMatch(in:) and a regex that matches a title-case word to search for such a word at the start of different strings: let titleCaseWord = /[A-Z][A-Za-z]+/

if let wordMatch = try titleCaseWord.prefixMatch(in: "Searching in a Regex") {     print(wordMatch.0) } else {     print("No match.") } // Prints "Searching"

if let wordMatch = try titleCaseWord.prefixMatch(in: "title case word at the End") {     print(wordMatch.0) } else {     print("No match.") } // Prints "No match." The prefixMatch(in:) method can throw an error if this regex includes a transformation closure that throws an error.