---
title: functionPrototype()
framework: metalperformanceshaders
role: symbol
role_heading: Instance Method
path: metalperformanceshaders/mpsfunction/functionprototype()
---

# functionPrototype()

## Declaration

```swift
func functionPrototype() -> String
```

## Discussion

Discussion Get a source level representation of the function prototype If your application is building its shaders from source at run time, this string will declare the appropriate function prototypes for the conversion routine appropriate to the version of MetalHDR you are currently running.          Note: It is expected that most applications will not use this interface because they          are building kernels offline from a .metallib. Such applications should simply:

#include <MPSFunctions/MPSFunctions.h>

in their .metal file, and declare any functions produced by this object using

MPSFUNCTION_DECLARE_COLOR_CONVERSION( _functionName );

or similar, depending on the type of the function created. The _functionName should          match the name passed to the object -init method.