---
layout: docs
title: lambda
id: class.Facebook.HackCodegen.HackBuilderKeys.lambda
docid: class.Facebook.HackCodegen.HackBuilderKeys.lambda
permalink: /docs/reference/class.Facebook.HackCodegen.HackBuilderKeys.lambda/
---
# Facebook\\HackCodegen\\HackBuilderKeys::lambda()




The key will be rendered with the specified lambda




``` Hack
public static function lambda<T as arraykey>(
  callable $render,
): IHackBuilderKeyRenderer<T>;
```




## Parameters




+ ` callable $render `




## Returns




* ` IHackBuilderKeyRenderer<T> `