---
title: "leadSurrogate(_:)"
framework: swift
role: symbol
role_heading: Type Method
path: "swift/unicode/utf16/leadsurrogate(_:)"
---

# leadSurrogate(_:)

Returns the high-surrogate code unit of the surrogate pair representing the specified Unicode scalar.

## Declaration

```swift
static func leadSurrogate(_ x: Unicode.Scalar) -> UTF16.CodeUnit
```

## Parameters

- `x`: A Unicode scalar value. x must be represented by a surrogate pair when encoded in UTF-16. To check whether x is represented by a surrogate pair, use UTF16.width(x) == 2.

## Return Value

Return Value The leading surrogate code unit of x when encoded in UTF-16.

## Discussion

Discussion Because a Unicode scalar value can require up to 21 bits to store its value, some Unicode scalars are represented in UTF-16 by a pair of 16-bit code units. The first and second code units of the pair, designated leading and trailing surrogates, make up a surrogate pair. let apple: Unicode.Scalar = "🍎" print(UTF16.leadSurrogate(apple)) // Prints "55356"