---
title: "prefix(while:)"
framework: swift
role: symbol
role_heading: Instance Method
path: "swift/lazydropwhilesequence/prefix(while:)"
---

# prefix(while:)

Returns a lazy sequence of the initial consecutive elements that satisfy predicate.

## Declaration

```swift
func prefix(while predicate: @escaping (Self.Elements.Element) -> Bool) -> LazyPrefixWhileSequence<Self.Elements>
```

## Parameters

- `predicate`: A closure that takes an element of the sequence as its argument and returns true if the element should be included or false otherwise. Once predicate returns false it will not be called again.