# makeFunction(name:) Creates an instance that represents a shader function in the library. ``` func makeFunction(name functionName: String) -> (any MTLFunction)? ``` ## Parameters `functionName` The name of the function. ## Return Value An [`MTLFunction`](/documentation/Metal/MTLFunction), or `nil` if the named function isn’t found in the library. ## Discussion If you call this method to retrieve a function that doesn’t use function constants, it returns an [`MTLFunction`](/documentation/Metal/MTLFunction) instance that you can use to build a render or compute pipeline. If you call this method to retrieve a function that uses function constants to specialize its behavior, you can only use the returned instance to query the `functionConstants` property for the list of function constants. You can’t use to create a render or compute pipeline. To get a specialized instance that you can use to create a pipeline instance, call the [`makeFunction(name:constantValues:completionHandler:)`](/documentation/Metal/MTLLibrary/makeFunction(name:constantValues:completionHandler:)) method or [`makeFunction(name:constantValues:)`](/documentation/Metal/MTLLibrary/makeFunction(name:constantValues:)) to generate a specialized function. ## See Also [Metal Shading Language Guide](https://developer.apple.com/library/archive/documentation/Metal/Reference/MetalShadingLanguageGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40014364) [Metal Programming Guide](https://developer.apple.com/library/archive/documentation/Miscellaneous/Conceptual/MetalProgrammingGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40014221) --- 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)